The reproduction of plants and animals appears to be of two kinds, solitary and sexual; the former occurs in the formation of the buds of trees, and the bulbs of tulips; which for several successions generate other buds, and other bulbs, nearly similar to the parent, but constantly approaching to greater perfection, so as finally to produce sexual organs, or flowers, and consequent seeds.
The same occurs in some inferior kinds of animals; as the aphises in the spring and summer are viviparous for eight or nine generations, which successively produce living descendants without sexual intercourse, and are themselves, I suppose, without sex; at length in the autumn they propagate males and females, which copulate and lay eggs, which lie dormant during the winter, and are hatched by the vernal sun; while the truffle, and perhaps mushrooms amongst vegetables, and the polypus and taenia amongst insects, perpetually propagate themselves by solitary reproduction, and have not yet acquired male and female organs.
Philosophers have thought these viviparous aphides, and the taenia, and volvox, to be females; and have supposed them to have been impregnated long before their nativity within each other; so the taenia and volvox still continue to produce their offspring without sexual intercourse. One extremity of the taenia, is said by Linneus to grow old, whilst at the other end new ones are generated proceeding to infinity like the roots of grass. The volvox globator is transparent, and carries within itself children and grandchildren to the fifth generation like the aphides; so that the taenia produces children and grandchildren longitudinally in a chain-like series, and the volvox propagates an offspring included within itself to the fifth generation; Syst. Nat.
Many microscopic animals, and some larger ones, as the hydra or polypus, are propagated by splitting or dividing; and some still larger animals, as oysters, and perhaps eels, have not yet acquired sexual organs, but produce a paternal progeny, which requires no mother to supply it with a nidus, or with nutriment and oxygenation; and, therefore, very accurately resemble the production of the buds of trees, and the wires of some herbaceous plants, as of knot-grass and of strawberries, and the bulbs of other plants, as of onions and potatoes; which is further treated of in Phytologia, Sect. VII.
The manner in which I suspect the solitary reproduction of the buds of trees to be effected, may also be applied to the solitary generation of the insects mentioned above, and probably of many others, perhaps of all the microscopic ones. It should be previously observed, that many insects are hermaphrodite, possessing both male and female organs of reproduction, as shell-snails and dew-worms; but that these are seen reciprocally to copulate with each other, and are believed not to be able to impregnate themselves; which belongs, therefore, to sexual generation, and not to the solitary reproduction of which I am now speaking.
As in the chemical production of any new combination of matter, two kinds of particles appear to be necessary; one of which must possess the power of attraction, and the other the aptitude to be attracted, as a magnet and a piece of iron; so in vegetable or animal combinations, whether for the purpose of nutrition or for reproduction, there must exist also two kinds of organic matter; one possessing the appetency to unite, and the other the propensity to be united; (see Zoonomia, octavo edition, Sect. XXXIX. 8.) Hence in the generation of the buds of trees, there are probably two kinds of glands, which acquire from the vegetable blood, and deposite beneath the cuticle of the tree two kinds of formative organic matter, which unite and form parts of the new vegetable embryon; which again uniting with other such organizations form the caudex, or the plumula, or the radicle, of a new vegetable bud.
A similar mode of reproduction by the secretion of two kinds of organic particles from the blood, and by depositing them either internally as in the vernal and summer aphis or volvox, or externally as in the polypus and taenia, probably obtains in those animals; which are thence propagated by the father only, not requiring a cradle, or nutriment, or oxygenation from a mother; and that the five generations, said to be seen in the transparent volvox globator within each other, are perhaps the successive progeny to be delivered at different periods of time from the father, and erroneously supposed to be mothers impregnated before their nativity.
II. Sexual as well as solitary reproduction appears to be effected by two kinds of glands; one of which collects or secretes from the blood formative organic particles with appetencies to unite, and the other formative organic particles with propensities to be united. These probably undergo some change by a kind of digestion in their respective glands; but could not otherwise unite previously in the mass of blood from its perpetual motion.
The first mode of sexual reproduction seems to have been by the formation of males into hermaphrodites; that is, when the numerous formative glands, which existed in the caudex of the bud of a tree, or on the surface of a polypus, became so united as to form but two glands; which might then be called male and female organs. But they still collect and secrete their adapted particles from the same mass of blood as in snails and dew-worms, but do not seem to be so placed as to produce an embryon by the mixture of their secreted fluids, but to require the mutual assistance of two hermaphrodites for that purpose.
From this view-of the subject, it would appear that vegetables and animals were at first propagated by solitary generation, and afterwards by hermaphrodite sexual generation; because most vegetables possess at this day both male and female organs in the same flower, which Linneus has thence well called hermaphrodite flowers; and that this hermaphrodite mode of reproduction still exists in many insects, as in snails and worms; and, finally, because all the male quadrupeds, as well as men, possess at this day some remains of the female apparatus, as the breasts with nipples, which still at their nativity are said to be replete with a kind of milk, and the nipples swell on titillation.
Afterwards the sexes seem to have been formed in vegetables as in flowers, in addition to the power of solitary reproduction by buds. So in animals the aphis is propagated both by solitary reproduction as in spring, or by sexual generation as in autumn; then the vegetable sexes began to exist in separate plants, as in the classes monoecia and dioecia, or both of them in the same plant also, as in the class polygamia; but the larger and more perfect animals are now propagated by sexual reproduction only, which seems to have been the chef-d'oeuvre, or capital work of nature; as appears by the wonderful transformations of leaf-eating caterpillars into honey-eating moths and butterflies, apparently for the sole purpose of the formation of sexual organs, as in the silk-worm, which takes no food after its transformation, but propagates its species and dies.
The microscopic productions of spontaneous vitality, and the next most inferior kinds of vegetables and animals, propagate by solitary generation only; as the buds and bulbs raised immediately from seeds, the lycoperdon tuber, with probably many other fungi, and the polypus, volvox, and taenia. Those of the next order propagate both by solitary and sexual reproduction, as those buds and bulbs which produce flowers as well as other buds or bulbs; and the aphis, and probably many other insects. Whence it appears, that many of those vegetables and animals, which are produced by solitary generation, gradually become more perfect, and at length produce a sexual progeny.
A third order of organic nature consists of hermaphrodite vegetables and animals, as in those flowers which have anthers and stigmas in the same corol; and in many insects, as leeches, snails, and worms; and perhaps all those reptiles which have no bones, according to the observation of M. Poupart, who thinks, that the number of hermaphrodite animals exceeds that of those which are divided into sexes; Mem. de l'Acad. des Sciences. These hermaphrodite insects I suspect to be incapable of impregnating themselves for reasons mentioned in Zoonomia, Sect. XXXIX. 6. 2.
And, lastly, the most perfect orders of animals are propagated by sexual intercourse only; which, however, does not extend to vegetables, as all those raised from seed produce some generations of buds or bulbs, previous to their producing flowers, as occurs not only in trees, but also in the annual plants. Thus three or four joints of wheat grow upon each other, before that which produces a flower; which joints are all separate plants growing over each other, like the buds of trees, previous to the uppermost; though this happens in a few months in annual plants, which requires as many years in the successive buds of trees; as is further explained in Phytologia, Sect. IX. 3. 1.
Where climate is favourable, and salubrious food plentiful, there is reason to believe, that the races of animals perpetually improve by reproduction. The smallest microscopic animals become larger ones in a short time, probably by successive reproductions, as is so distinctly seen in the buds of seedling apple-trees, and in the bulbs of tulips raised from seed; both which die annually, and leave behind them one or many, which are more perfect than themselves, till they produce a sexual progeny, or flowers. To which may be added, the rapid improvement of our domesticated dogs, horses, rabbits, pigeons, which improve in size, or in swiftness, or in the sagacity of the sense of smell, or in colour, or other properties, by sexual reproduction.
The great Linneus having perceived the changes produced in the vegetable world by sexual reproduction, has supposed that not more than about sixty plants were at first created, and that all the others have been formed by their solitary or sexual reproductions; and adds, Suadent haec Creatoris leges a simplicibus ad composita; Gen. Plant. preface to the natural orders, and Amenit. Acad. VI. 279. This mode of reasoning may be extended to the most simple productions of spontaneous vitality.
There is one curious circumstance of animal life analogous in some degree to this wonderful power of reproduction; which is seen in the propagation of some contagious diseases. Thus one grain of variolous matter, inserted by inoculation, shall in about seven days stimulate the system into unnatural action; which in about seven days more produces ten thousand times the quantity of a similar material thrown out on the skin in pustules!
The mystery of reproduction, which alone distinguishes organic life from mechanic or chemic action, is yet wrapt in darkness. During the decomposition of organic bodies, where there exists a due degree of warmth with moisture, new microscopic animals of the most minute kind are produced; and these possess the wonderful power of reproduction, or of producing animals similar to themselves in their general structure, but with frequent additional improvements; which the preceding parent might in some measure have acquired by his habits of life or accidental situation.
But it may appear too bold in the present state of our knowledge on this subject, to suppose that all vegetables and animals now existing were originally derived from the smallest microscopic ones, formed by spontaneous vitality? and that they have by innumerable reproductions, during innumerable centuries of time, gradually acquired the size, strength, and excellence of form and faculties, which they now possess? and that such amazing powers were originally impressed on matter and spirit by the great Parent of Parents! Cause of Causes! Ens Entium!
ADDITIONAL NOTES. IX.
And Heaven-born STORGE weaves the social chain. CANTO II. l. 92.
The Greek word Storge is used for the affection of parents to children; which was also visibly represented by the Stork or Pelican feeding her young with blood taken from her own wounded bosom. A number of Pelicans form a semicircle in shallow parts of the sea near the coast, standing on their long legs; and thus including a shoal of small fish, they gradually approach the shore; and seizing the fish as they advance, receive them into a pouch under their throats; and bringing them to land regurgitate them for the use of their young, or for their future support. Adanson, Voyage to Senegal. In this country the parent Pigeons both male and female swallow the grain or other seeds, which they collect for their young, and bring it up mixed with a kind of milk from their stomachs, with their bills inserted into the mouths of the young doves. J. Hunter's works.
The affection of the parent to the young in experienced mothers may be in part owing to their having been relieved by them from the burden of their milk; but it is difficult to understand, how this affection commences in those mothers of the bestial world, who have not experienced this relief from the sucking of their offspring; and still more so to understand how female birds were at first induced to incubate their eggs for many weeks; and lastly how caterpillars, as of the silk-worm, are induced to cover themselves with a well-woven house of silk before their transformation.
These as well as many other animal facts, which are difficult to account for, have been referred to an inexplicable instinct; which is supposed to preclude any further investigation: but as animals seem to have undergone great changes, as well as the inanimate parts of the earth, and are probably still in a state of gradual improvement; it is not unreasonable to conclude, that some of these actions both of large animals and of insects, may have been acquired in a state preceding their present one; and have been derived from the parents to their offspring by imitation, or other kind of tradition; thus the eggs of the crocodile are at this day hatched by the warmth of the sun in Egypt; and the eggs of innumerable insects, and the spawn of fish, and of frogs, in this climate are hatched by the vernal warmth: this might be the case of birds in warm climates, in their early state of existence; and experience might have taught them to incubate their eggs, as they became more perfect animals, or removed themselves into colder climates: thus the ostrich is said to sit upon its eggs only in the night in warm situations, and both day and night in colder ones.
This love of the mother in quadrupeds to the offspring, whom she licks and cleans, is so allied to the pleasure of the taste or palate, that nature seems to have had a great escape in the parent quadruped not devouring her offspring. Bitches, and cats, and sows, eat the placenta; and if a dead offspring occurs, I am told, that also is sometimes eaten, and yet the living offspring is spared; and by that nice distinction the progenies of those animals are saved from destruction!
"Certior factus sum a viro rebus antiquissimis docto, quod legitur in Berosi operibus homines ante diluvium mulierum puerperarum placentam edidisse, quasi cibum delicatum in epulis luxuriosis; et quod hoc nefandissimo crimine movebatur Deus diluvio submergere terrarum incolas." ANON.
It may be finally concluded, that this affection from the parent to the progeny existed before animals were divided into sexes, and produced the beginning of sympathetic society, the source of which may perhaps be thus well accounted for; whenever the glandular system is stimulated into greater natural action within certain limits, an addition of pleasure is produced along with the increased secretion; this pleasure arising from the activity of the system is supposed to constitute the happiness of existence, in contradistinction to the ennui or taedium vitae; as shown in Zoonomia, Sect. XXXIII. 1.
Hence the secretion of nutritious juices occasioned by the stimulus of an embryon or egg in the womb gives pleasure to the parent for a length of time; whence by association a similar pleasure may be occasioned to the parent by seeing and touching the egg or fetus after its birth; and in lactescent animals an additional pleasure is produced by the new secretion of milk, as well as by its emission into the sucking lips of the infant. This appears to be one of the great secrets of Nature, one of those fine, almost invisible cords, which have bound one animal to another.
The females of lactiferous animals have thus a passion or inlet of pleasure in their systems more than the males, from their power of giving suck to their offspring; the want of the object of this passion, either owing to the death of the progeny, or to the unnatural fashion of their situation in life, not only deprives them of this innocent and virtuous source of pleasure; but has occasioned diseases, which have been fatal to many of them.
ADDITIONAL NOTES. X.
EVE FROM ADAM'S RIB.
Form'd a new sex, the mother of mankind. CANTO II. l. 140.
The mosaic history of Paradise and of Adam and Eve has been thought by some to be a sacred allegory, designed to teach obedience to divine commands, and to account for the origin of evil, like Jotham's fable of the trees; Judges ix. 8. or Nathan's fable of the poor man and his lamb; 2 Sam. xii. 1. or like the parables in the New Testament; as otherwise knowledge could not be said to grow upon one tree, and life upon another, or a serpent to converse; and lastly that this account originated with the magi or philosophers of Egypt, with whom Moses was educated, and that this part of the history, where Eve is said to have been made from a rib of Adam might have been an hieroglyphic design of the Egyptian philosophers, showing their opinion that Mankind was originally of both sexes united, and was afterwards divided into males and females: an opinion in later times held by Plato, and I believe by Aristotle, and which must have arisen from profound inquiries into the original state of animal existence.
ADDITIONAL NOTES. XI.
The feeble births acquired diseases chase, Till Death extinguish the degenerate race. CANTO II. l. 165.
As all the families both of plants and animals appear in a state of perpetual improvement or degeneracy, it becomes a subject of importance to detect the causes of these mutations.
The insects, which are not propagated by sexual intercourse, are so few or so small, that no observations have been made on their diseases; but hereditary diseases are believed more to affect the offspring of solitary than of sexual generation in respect to vegetables; as those fruit trees, which have for more than a century been propagated only by ingrafting, and not from seeds, have been observed by Mr. Knight to be at this time so liable to canker, as not to be worth cultivation. From the same cause I suspect the degeneracy of some potatoes and of some strawberries to have arisen; where the curled leaf has appeared in the former, and barren flowers in the latter.
This may arise from the progeny by solitary reproduction so much more exactly resembling the parent, as is well seen in grafted trees compared with seedling ones; the fruit of the former always resembling that of the parent tree, but not so of the latter. The grafted scion also accords with the branch of the tree from whence it was taken, in the time of its bearing fruit; for if a scion be taken from a bearing branch of a pear or apple tree, I believe, it will produce fruit even the next year, or that succeeding; that is, in the same time that it would have produced fruit, if it had continued growing on the parent tree; but if the parent pear or apple tree has been cut down or headed, and scions are then, taken from the young shoots of the stem, and ingrafted; I believe those grafted trees will continue to grow for ten or twelve years, before they bear fruit, almost as long as seedling trees, that is they will require as much time, as those new shoots from the lopped trunk would require, before they produce fruit. It should thence be inquired, when grafted fruit trees are purchased, whether the scions were taken from bearing branches, or from the young shoots of a lopped trunk; as the latter, I believe, are generally sold, as they appear stronger plants. This greater similitude of the progeny to the parent in solitary reproduction must certainly make them more liable to hereditary diseases, if such have been acquired by the parent from unfriendly climate or bad nourishment, or accidental injury.
In respect to the sexual progeny of vegetables it has long been thought, that a change of seed or of situation is in process of time necessary to prevent their degeneracy; but it is now believed, that it is only changing for seed of a superior quality, that will better the product. At the same time it may be probably useful occasionally to intermix seeds from different situations together; as the anther-dust is liable to pass from one plant to another in its vicinity; and by these means the new seeds or plants may be amended, like the marriages of animals into different families.
As the sexual progeny of vegetables are thus less liable to hereditary diseases than the solitary progenies; so it is reasonable to conclude, that the sexual progenies of animals may be less liable to hereditary diseases, if the marriages are into different families, than if into the same family; this has long been supposed to be true, by those who breed animals for sale; since if the male and female be of different temperaments, as these are extremes of the animal system, they may counteract each other; and certainly where both parents are of families, which are afflicted with the same hereditary disease, it is more likely to descend to their posterity.
The hereditary diseases of this country have many of them been the consequence of drinking much fermented or spirituous liquor; as the gout always, most kinds of dropsy, and, I believe, epilepsy, and insanity. But another material, which is liable to produce diseases in its immoderate use, I believe to be common salt; the sea-scurvy is evidently caused by it in long voyages; and I suspect the scrofula, and consumption, to arise in the young progeny from the debility of the lymphatic and venous absorption produced in the parent by this innutritious fossile stimulus. The petechiae and vibices in the sea-scurvy and occasional haemorrhages evince the defect of venous absorption; the occasional haemoptoe at the commencement of pulmonary consumption, seems also to arise from defect of venous absorption; and the scrofula, which arises from the inactivity of the lymphatic absorbent system, frequently exists along with pulmonary as well as with mesenteric consumption. A tendency to these diseases is certainly hereditary, though perhaps not the diseases themselves; thus a less quantity of ale, cyder, wine, or spirit, will induce the gout and dropsy in those constitutions, whose parents have been intemperate in the use of those liquors; as I have more than once had occasion to observe.
Finally the art to improve the sexual progeny of either vegetables or animals must consist in choosing the most perfect of both sexes, that is the most beautiful in respect to the body, and the most ingenious in respect to the mind; but where one sex is given, whether male or female, to improve a progeny from that person may consist in choosing a partner of a contrary temperament.
As many families become gradually extinct by hereditary diseases, as by scrofula, consumption, epilepsy, mania, it is often hazardous to marry an heiress, as she is not unfrequently the last of a diseased family.
ADDITIONAL NOTES. XII.
CHEMICAL THEORY OF ELECTRICITY AND MAGNETISM.
Then mark how two electric streams conspire To form the resinous and vitreous fire. CANTO III. l. 21.
I. Of Attraction and Repulsion.
The motions, which accomplish the combinations and decompositions of bodies, depend on the peculiar attractions and repulsions of the particles of those bodies, or of the sides and angles of them; while the motions of the sun and planets, of the air and ocean, and of all bodies approaching to a general centre or retreating from it, depend on the general attraction or repulsion of those masses of matter. The peculiar attractions above mentioned are termed chemical affinities, and the general attraction is termed gravitation; but the peculiar repulsions of the particles of bodies, or the general repulsion of the masses of matter, have obtained no specific names, nor have been sufficiently considered; though they appear to be as powerful agents as the attractions.
The motions of ethereal fluids, as of magnetism and electricity, are yet imperfectly understood, and seem to depend both on chemical affinity, and on gravitation; and also on the peculiar repulsions of the particles of bodies, and on the general repulsion of the masses of matter.
In what manner attraction and repulsion are produced has not yet been attempted to be explained by modern philosophers; but as nothing can act, where it does not exist, all distant attraction of the particles of bodies, as well as general gravitation, must be ascribed to some still finer ethereal fluid; which fills up all space between the suns and their planets, as well as the interstices of coherent matter. Repulsion in the same manner must consist of some finer ethereal fluid; which at first projected the planets from the sun, and I suppose prevents their return to it; and which occasionally volatilizes or decomposes solid bodies into fluid or aerial ones, and perhaps into ethereal ones.
May not the ethereal matter which constitutes repulsion, be the same as the matter of heat in its diffused state; which in its quiescent state is combined with various bodies, as appears from many chemical explosions, in which so much heat is set at liberty? The ethereal matter, which constitutes attraction, we are less acquainted with; but it may also exist combined with bodies, as well as in its diffused state; since the specific gravities of some metallic mixtures are said not to accord with what ought to result from the combination of their specific gravities, which existed before their mixture; but their absolute gravities have not been attended to sufficiently; as these have always been supposed to depend on their quantity of matter, and situation in respect to the centre of the earth.
The ethereal fluids, which constitute peculiar repulsions and attractions, appear to gravitate round the particles of bodies mixed together; as those, which constitute the general repulsion or attraction, appear to gravitate round the greater masses of matter mixed together; but that which constitutes attraction seems to exist in a denser state next to the particles or masses of matter; and that which constitutes repulsion to exist more powerfully in a sphere further from them; whence many bodies attract at one distance, and repel at another. This may be observed by approaching to each other two electric atmospheres round insulated cork-balls; or by pressing globules of mercury, which roll on the surface, till they unite with it; or by pressing the drops of water,' which stand on a cabbage leaf, till they unite with it, and hence light is reflected from the surface of a mirror without touching it.
Thus the peculiar attractions and repulsions of the particles of bodies, and the general ones of the masses of matter, perpetually oppose and counteract each other; whence if the power of attraction should cease to act, all matter would be dissipated by the power of repulsion into boundless space; and if heat, or the power of repulsion, should cease to act, the whole world would become one solid mass, condensed into a point.
II. Preliminary Propositions.
The following propositions concerning Electricity and Galvanism will either be proved by direct experiments, or will be rendered probable by their tending to explain or connect the variety of electric facts, to which they will be applied.
1. There are two kinds of electric ether, which exist either separately or in combination. That which is accumulated on the surface of smooth glass, when it is rubbed with a cushion, is here termed vitreous ether; and that which is accumulated on the surface of resin or sealing-wax, when it is rubbed with a cushion, is here termed resinous ether; and a combination of them, as in their usual state, may be termed neutral electric ethers.
2. Atmospheres of vitreous or of resinous or of neutral electricity surround all separate bodies, are attracted by them, and permeate those, which are called conductors, as metallic and aqueous and carbonic ones; but will not permeate those, which are termed nonconductors, as air, glass, silk, resin, sulphur.
3. The particles of vitreous electric ether strongly repel each other as they surround other bodies; but strongly attract the particles of resinous electric ether: in similar manner the particles of the resinous ether powerfully repel each other, and as powerfully attract those of the vitreous ether. Hence in their separate state they appear to occupy much greater space, as they, gravitate round insulated bodies, and are then only cognizable by our senses or experiments. They rush violently together through conducting substances, and then probably possess much less space in this their combined state. They thus resemble oxygen gas and nitrous gas; which rush violently together when in contact; and occupy less space when united, than either of them possessed separately before their union. When the two electric ethers thus unite, a chemical explosion occurs, like an ignited train of gunpowder; as they give out light and heat; and rend or fuse the bodies they occupy; which cannot be accounted for on the mechanical theory of Dr. Franklin.
4. Glass holds within it in combination much resinous electric ether, which constitutes a part of it, and which more forcibly attracts vitreous electric ether from surrounding bodies, which stands on it mixed with a less proportion of resinous ether like an atmosphere, but cannot unite with the resinous ether, which is combined with the glass; and resin, on the contrary, holds within it in combination much vitreous electric ether, which constitutes a part of it, and which more forcibly attracts resinous electric ether from surrounding bodies, which stands on it mixed with a less proportion of vitreous ether like an atmosphere, but cannot unite with the vitreous ether, which is combined with the resin.
As in the production of vitrification, those materials are necessary which contain much oxygen, as minium, and manganese; there is probably much oxygen combined with glass, which may thence be esteemed a solid acid, as water may be esteemed a fluid one. It is hence not improbable, that one kind of electric ether may also be combined with it, as it seems to affect the oxygen of water in the Galvanic experiments. The combination of the other kind of electric ether with wax or sulphur, is countenanced from those bodies, when heated or melted, being said to part with much electricity as they cool, and as it appears to affect the hydrogen in the decomposition of water by Galvanism.
5. Hence the nonconductors of electricity are of two kinds; such as are combined with vitreous ether, as resin, and sulphur; and such as are combined with resinous ether, as glass, air, silk. But both these kinds of nonconductors are impervious to either of the electric ethers; as those ethers being already combined with other bodies will not unite with each other, or be removed from their situations by each other. Whereas the perfect conducting bodies, as metals, water, charcoal, though surrounded with electric atmospheres, as they have neither of the electric ethers combined with them, suffer them to permeate and pass through them, whether separately or in their neutral state of reciprocal combination.
But it is probable, that imperfect conductors may possess more or less of either the vitreous or resinous ether combined with them, since their natural atmospheres are dissimilar as mentioned below; and that this makes them more or less imperfect conductors.
6. Those bodies which are perfect conductors, have probably neutral electric atmospheres gravitating round them consisting of an equal or saturated mixture of the two electric ethers, whereas the atmospheres round the nonconducting bodies probably consist of an unequal mixture of the electric ethers, as more of the vitreous one round glass, and more of the resinous one round resin; and, it is probable, that these mixed atmospheres, which surround imperfect conducting bodies, consist also of different proportions of the vitreous and resinous ethers, according to their being more or less perfect conductors. These minute degrees of the difference of these electric atmospheres are evinced by Mr. Bennet's Doubler of Electricity, as shown in his work, and are termed by him Adhesive Electric Atmospheres, to distinguish them from those accumulated by art; thus the natural adhesive electricity of silver is more of the vitreous kind compared with that of zinc, which consists of a greater proportion of the resinous; that is, in his language, silver is positive and zinc negative. This experiment I have successfully repeated with Mr. Bennet's Doubler along with Mr. Swanwick.
7. Great accumulation or condensation of the separate electric ethers attract each other so strongly, that they will break a passage through nonconducting bodies, as through a plate of glass, or of air, and will rend bodies which are less perfect conductors, and give out light and heat like the explosion of a train of gunpowder; whence, when a strong electric shock is passed through a quire of paper, a bur, or elevation of the sheets, is seen on both sides of it occasioned by the explosion. Whence trees and stone walls are burst by lightning, and wires are fused, and inflammable bodies burnt, by the heat given out along with the flash of light, which cannot be explained by the mechanic theory.
8. When artificial or natural accumulations of these separate ethers are very minute in quantity or intensity, they pass slowly and with difficulty from one body to another, and require the best conductors for this purpose; whence many of the phenomena of the torpedo or gymnotus, and of Galvanism. Thus after having discharged a coated jar, if the communicating wire has been quickly withdrawn, a second small shock may be taken after the principal discharge, and this repeatedly two or three times.
Hence the charge of the Galvanic pile being very minute in quantity or intensity, will not readily pass through the dry cuticle of the hands, though it so easily passes through animal flesh or nerves, as this combination of charcoal with water seems to constitute the most perfect conductor yet known.
9. As light is reflected from the surface of a mirror before it actually touches it, and as drops of water are repelled from cabbage leaves without touching them, and as oil lies on water without touching it, and also as a fine needle may be made to lie on water without touching it, as shown by Mr. Melville in the Literary Essays of Edinburgh; there is reason to believe, that the vitreous and resinous electric ethers are repelled by, or will not pass through, the surfaces of glass or resin, to which they are applied. But though neither of these electric ethers passes through the surfaces of glass or resin, yet their attractive or repulsive powers pass through them: as the attractive or repulsive power of the magnet to iron passes through the atmosphere, and all other bodies which exist between them. So an insulated cork-ball, when electrised either with vitreous or resinous ether, repels another insulated cork-ball electrised with the same kind of ether, through half an inch of common air, though these electric atmospheres do not unite.
Whence it may be concluded, that the general attractive and repulsive ethers accompany the electric ethers as well as they accompany all other bodies; and that the electric ethers do not themselves attract or repel through glass or resin, as they cannot pass through them, but strongly attract each other when they come into contact, rush together, and produce an explosion of the sudden liberation of heat and light.
III. Effect of Metallic Points.
1. When a pointed wire is presented by a person standing on the ground to an insulated conductor, on which either vitreous or resinous electricity is accumulated, the accumulated electricity will pass off at a much greater distance than if a metallic knob be fixed on the wire and presented in its stead.
2. The same occurs if the metallic point be fixed on the electrised conductor, and the finger of a person standing on the ground be presented to it, the accumulated electricity will pass off at a much greater distance, and indeed will soon discharge itself by communicating the accumulated electricity to the atmosphere.
3. If a metallic point be fixed on the prime conductor, and the flame of a candle be presented to it, on electrising the conductor either with vitreous or resinous ether, the flame of the candle is blown from the point, which must be owing to the electric fluid in its passage from the point carrying along with it a stream of atmospheric air.
The manner in which the accumulated electricity so readily passes off by a metallic point may be thus understood; when a metallic point stands erect from an electrised metallic plane, the accumulated electricity which exists on the extremity of the point, is attracted less than that on the other parts of the electrised surface. For the particle of electric matter immediately over the point is attracted by that point only, whereas the particles of electric matter over every other part of the electrised plane, is not only attracted by the parts of the plane immediately under them, but also laterally by the circumjacent parts of it; whence the accumulated electric fluid is pushed off at this point by that over the other parts being more strongly attracted to the plane.
Thus if a light insulated horizontal fly be constructed of wire with points fixed as tangents to the circle, it will revolve the way contrary to the direction of the points as long as it continues to be electrised. For the same reason as when a circle of cork, with a point of the cork standing from it like a tangent, is smeared with oil, and thrown upon a lake, it will continue to revolve backwards in respect to the direction of the point till all the oil is dispersed upon the lake, as first observed by Dr. Franklin; for the oil being attracted to all the other parts of the cork-circle more than towards the pointed tangent, that part over the point is pushed off and diffuses itself on the water, over which it passes without touching, and consequently without friction; and thus the cork revolves in the contrary direction.
As the flame of a candle is blown from a point fixed on an electrised conductor, whether vitreous or resinous electricity is accumulated on it, it shows that in both cases electricity passes from the point, which is a forcible argument against the mechanical theory of positive and negative electricity; because then the flame should be blown towards the point in one case, and from it in the other.
So the electric fly, as it turns horizontally, recedes from the direction of the points of the tangents, whether it be electrised with vitreous or resinous electricity; whereas if it was supposed to receive electricity, when electrised by resin, and to part with it when electrised by glass, it ought to revolve different ways; which also forcibly opposes the theory of positive and negative electricity.
As an electrised point with either kind of electricity causes a stream of air to pass from it in the direction of the point, it seems to affect the air much in the same manner as the fluid matter of heat affects it; that is, it will not readily pass through it, but will adhere to the particles of air, and is thus carried away with them.
From this it will also appear, that points do not attract electricity, properly speaking, but suffer it to depart from them; as it is there less attracted to the body which it surrounds, than by any other part of the surface.
And as a point presented to an electrised conductor facilitates the discharge of it, and blows the flame of a candle towards the conductor, whether vitreous or resinous electricity be accumulated upon it; it follows, that in both cases some electric matter passes from the point to the conductor, and that hence there are two electric ethers; and that they combine or explode when they meet together, and give out light and heat, and occupy less space in this their combined state, like the union of nitrous gas with oxygen gas.
IV. Accumulation of Electric Ethers by Contact.
The electric ethers may be separately accumulated by contact of conductors with nonconductors, by vicinity of the two ethers, by heat, and by decomposition.
Glass is believed to consist in part of consolidated resinous ether, and thence to attract an electric atmosphere round it, which consists of a greater proportion of vitreous ether compared to the quantity of the resinous, as mentioned in Proposition No. 4. This atmosphere may stand off a line from the surface of the glass, though its attractive or repulsive power may extend to a much greater distance; and a more equally mixed electric atmosphere may stand off about the same distance from the surface of a cushion.
Now when a cushion is forcibly pressed upon the surface of a glass cylinder or plane, the atmosphere of the cushion is forced within that of the glass, and consequently the vitreous part of it is brought within the sphere of the attraction of the resinous ether combined with the glass, and therefore becomes attracted by it in addition to the vitreous part of the spontaneous atmosphere of the glass; and the resinous part of the atmosphere of the cushion is at the same time repelled by its vicinity to the combined resinous ether of the glass. From both which circumstances a vitreous ether alone surrounds the part of the glass on which the cushion is forcibly pressed; which does not, nevertheless, resemble an electrised coated jar; as this accumulation of vitreous ether on one side of the glass is not so violently condensed, or so forcibly attracted to the glass by the loose resinous ether on the other side of it, as occurs in the charged coated jar.
Hence as weak differences of the kinds or quantities of electricity do not very rapidly change place, if the cushion be suddenly withdrawn, with or without friction, I suppose an accumulation of vitreous electric ether will be left on the surface of the glass, which will diffuse itself on an insulated conductor by the assistance of points, or will gradually be dissipated in the air, probably like odours by the repulsion of its own particles, or may be conducted away by the surrounding air as it is repelled from it, or by the moisture or other impurities of the atmosphere. And hence I do not suppose the friction of the glass-globe to be necessary, except for the purpose of more easily removing the parts of the surface from the pressure of the cushion to the points of the prime conductor, and to bring them more easily into reciprocal contact.
When sealing wax or sulphur is rubbed by a cushion, exactly the same circumstance occurs, but with the different ethers; as the resinous ether of the spontaneous atmosphere of the cushion, when it is pressed within the spontaneous atmosphere of the sealing wax, is attracted by the solid vitreous ether, which is combined with it; and at the same time the vitreous ether of the cushion is repelled by it; and hence an atmosphere of resinous ether alone exists between the sealing wax and the cushion thus pressed together. It is nevertheless possible, that friction on both sealing wax and glass may add some facility to the accumulations of their opposite ethers by the warmth which it occasions. As most electric machines succeed best after being warmed, I think even in dry frosty seasons.
Though when a cushion is applied to a smooth surfaced glass, so as to intermix their electric atmospheres, the vitreous ether of the cushion is attracted by the resinous ether combined with the glass; but does not intermix with it, but only adheres to it: and as the glass turns round, the vitreous electric atmosphere stands on the solid resinous electric ether combined with the glass; and is taken away by the metallic points of the prime conductor.
Yet if the surface of the glass be roughened by scratching it with a diamond or with hard sand, a new event occurs; which is, that the vitreous ether attracted from the cushion by the resinous ether combined with the glass becomes adhesive to it; and stands upon the roughened glass, and will not quit the glass to go to the prime conductor; whence the surface of the glass having a vitreous electric atmosphere united, as it were, to its inequalities, becomes similar to resin; and will now attract resinous electric ether, like a stick of sealing wax, without combining with it. Whence this curious and otherwise unintelligible phenomenon, that smooth surfaced glass will give vitreous electric ether to an insulated conductor, and glass with a roughened surface will give resinous ether to it.
V. Accumulation of electric ethers by vicinity.
Though the contact of a cushion on the whirling glass is the easiest method yet in use for the accumulation of the vitreous electric ether on an insulated conductor; yet there are other methods of effecting this, as by the vicinity of the two electric ethers with a nonconductor between them.
Thus I believe a great quantity of both vitreous and resinous electric ether may be accumulated in the following manner. Let a glass jar be coated within in the usual manner; but let it have a loose external coating, which can easily be withdrawn by an insulating handle. Then charge the jar, as highly as it may be, by throwing into it vitreous electric ether; and in this state hermetically seal it, if practicable, otherwise close it with a glass stopple and wax. When the external coating is drawn off by an insulating handle, having previously had a communication with the earth, it will possess an accumulation of resinous electric ether; and then touching it with your finger, a spark will be seen, and there will cease to be any accumulated ether.
Thus by alternately replacing this loose coating, and withdrawing it from the sealed charged jar, by means of an insulating handle; and by applying it to one insulated conductor, when it is in the vicinity of the jar; and to another insulated conductor, when it is withdrawn; vitreous electric ether may be accumulated on one of them, and resinous on the other; and thus I suspect an immense quantity of both ethers may be produced without friction or much labour, if a large electric battery was so contrived; and that it might be applied to many mechanical purposes, where other explosions are now used, as in the place of steam engines, or to rend rocks, or timber, or destroy invading armies!
The principle of this mode of accumulating the two electric ethers in some measure resembles that of Volta's Electrophorus and Bennet's Doubler.
VI. Accumulation of electric ethers by heat and by decomposition.
When glass or amber is heated by the fire in a dry season, I suspect that it becomes in some degree electric; as either of the electric ethers which is combined with them may have its combination with those materials loosened by the application of heat; and that on this account they may more forcibly attract the opposite one from the air in their vicinity.
It has long been known, that a siliceous stone called the tourmalin, when its surfaces are polished, if it be laid down before the fire, will become electrified with vitreous, or what is called positive electricity on its upper surface; and resinous, or what is called negative electricity on its under surface; which I suppose lay in contact with somewhat which supported it near the fire.
In this experiment I suppose the tourmalin to be naturally combined with resinous electric ether like glass; which on one side next towards the fire by the increase of its attractive power, owing to the heat having loosened its combination with the earth of the stone, more strongly attracts vitreous electric ether from the atmosphere; which now stands on its surface: and then as the lower surface of the stone lies in contact with the hearth, the less quantity of vitreous ether is there repelled by the greater quantity of it on the upper surface; while the resinous ether is attracted by it: and the stone is thus charged like a coated jar with vitreous electric ether condensed on one side of it, and resinous on the other.
So cats, as they lie by the fire in a frosty day, become so electric as frequently to give a perceptible spark to one's finger from their ears without friction.
A fourth method of separating the two ethers would seem to be by the decomposition of metallic bodies, as in the experiment with Volta's Galvanic pile; which is said by Mr. Davy to act so much more powerfully, when an acid is added to the water used in the experiment; as will be spoken of below.
From experiments made by M. Saussure on the electricity of evaporated water from hot metallic vessels, and from those of china and glass, he found when the vessel was calcined or made rusty by the evaporating water, that the electricity of it was positive (or vitreous), and that from china or glass was negative (or resinous), Encyclop. Britan. Art. Elect. No. 206, which seems also to show, that vitreous electric ether was given out or produced by the corrosion of metals, and resinous ether from the evaporation of water.
VII. The spark from the conductor, and of electric light.
When either the vitreous or resinous electric ether is accumulated on an insulated conductor, and an uninsulated conductor, as the finger of an attendant, is applied nearly in contact with it, what happens? The attractive and repulsive powers of the accumulated electric ether pass through the nonconducting plate of air, and if it be of the vitreous kind, it attracts the resinous electric ether of the finger towards it, and repels the vitreous electric ether of the finger from it.
Hence there exists for an instant a charged plate of air between the finger and the prime conductor, with an accumulation of vitreous ether on one side of it, and of resinous ether on the other side of it; and lastly these two kinds of electric ethers suddenly unite by their powerful attraction of each other, explode, and give out heat and light, and rupture the plate of nonconducting air, which separated them.
The rupture or disjunction of the plate of air is known by the sound of the spark, as of thunder; which shows that a vacuum of air was previously produced by the explosion of the electric fluids, and a vibration of the air in consequence of the sudden joining again of the sides of the vacuum.
The light which attends electric sparks and shocks, is not accounted for by the Theory of Dr. Franklin. I suspect that it is owing to the combination of the two electric ethers, from which as from all chemical explosions both light and heat are set at liberty, and because a smell is said to be perceptible from electric sparks, and even a taste which must be deduced from new combinations, or decompositions, as in other explosions: add to this that the same thing occurs, when electric shocks are passed through eggs in the dark, or through water, a luminous line is seen like the explosion of a train of gunpowder; lastly, whether light is really produced in the passage of the Galvanic electricity through the eyes, or that the sensation alone of light is perceived by its stimulating the optic nerve, has not yet been investigated; but I suspect the former, as it emits light from its explosion even in passing through eggs and through water, as mentioned above.
VIII. The shock from the coated jar, and of electric condensation.
1. When a glass jar is coated on both sides, and either vitreous or resinous electricity is thrown upon the coating on one side, and there is a communication to the earth from the other side, the same thing happens as in the plate of air between the finger and prime conductor above described; that is, the accumulated electricity, if it be of the vitreous kind, on one coating of the glass jar will attract the resinous part of the electricity, which surrounds or penetrates the coating on the other side of the jar, and also repel the vitreous part of it; but this occurs on a much more extensive surface than in the instance of the plate of air between the finger and prime conductor.
The difference between electric sparks and shocks consists in this circumstance, that in the former the insulating medium, whether of air, or of thin glass, is ruptured in one part, and thus a communication is made between the vitreous and resinous ethers, and they unite immediately, like globules of quicksilver, when pressed forcibly together: but in the electric shock a communication is made by some conducting body applied to the other extremities of the vitreous, and of the resinous atmospheres, through which they pass and unite, whether both sides of the coated jar are insulated, or only one side of it.
And in this line, as they reciprocally meet, they appear to explode and give out light and heat, and a new combination of the two ethers is produced, as a residuum after the explosion, which probably occupies much less space than either the vitreous or resinous ethers did separately before. At the same time there may be another unrestrainable ethereal fluid yet unobserved, given out from this explosion, which rends oak trees, bursts stone-walls, lights inflammable substances, and fuses metals, or dissipates them in a calciform smoak, along with which great light and much heat are emitted, or these effects are produced by the heat and light only thus set at liberty by their synchronous and sudden evolution.
2. The curious circumstance of electric condensation appears from the violence of the shock of the coated jar compared with the strongest spark from an insulated conductor, though the latter possesses a much greater surface; when vitreous electric ether is thrown on one side of a coated jar, it attracts the resinous electric ether of the other side of the coated jar; and the same occurs, when resinous ether is thrown on one side of it, it attracts the vitreous ether of the other side of it, and thus the vitreous electric ether on one side of the jar, and the resinous ether on the other side of it become condensed, that is accumulated in less space, by their reciprocal attraction of each other.
This condensation of the two electric ethers owing to their reciprocal attraction appears from another curious event, that the thinner the glass jar is, the stronger will the charge be on the same quantity of surface, as then the two ethers approaching nearer without their intermixing attract each other stronger, and consequently condense each other more. And when the glass jar is very thin the reciprocal attractive powers of the vitreous and resinous ether attract each other so violently as at length to pass through the glass by rupturing it, in the same manner as a less forcible attraction of them ruptures and passes through the plate of air in the production of sparks from the prime conductor.
As these two ethers on each side of a charged coated jar so powerfully attract each other, when a communication is made between them by some conducting substance as in the common mode of discharging an electrised coated jar, they reciprocally pass to each other for the purpose of combining, as some chemical fluids are known to do; as when nitrous gas and oxygen gas are mixed together; whence as these fluids pass both ways to intermix with each other, and then explode; a bur appears on each side of a quire of paper well pressed together, when a strong electric shock is passed through it; which is occasioned by their explosion, like a train of gunpowder, and consequent emission of some other ethereal fluid, either those of heat and light or of some new one not yet observed. Whence it becomes difficult to explain, according to the theory of Dr. Franklin, which way the electric fluid passed; and which side of the coated jar contained positive and which the negative charge according to that doctrine.
But the theory of the ingenious Dr. Franklin failed also in explaining other phenomena of the coated jar; since if the positive electricity accumulated on one side of the jar repelled the electricity from the coating on the other side of it, so as to produce an electric vacuum; why should it be so eager, when a communication is made by some conducting body, to run into that vacuum by its attraction or gravitation, which has been made by its repulsion; as thus it seems to be violently attracted by the vacuum, from which it had previously repelled a fluid similar to itself, which is not easily to be comprehended.
3. There is another mode by which either vitreous or resinous electric ether is capable of condensation; which consists in contracting the volume, so as to diminish the surface of the electrised body; as was ingeniously shown by Dr. Franklin's experiment of electrising a silver tankard with a length of chain rolled up within it; and then drawing up the chain by a silk string, which weakened the electric attraction of the tankard; which was strengthened again by returning the chain into it; thus the condensation of an electrised cloud is believed to condense the electric ether, which it contains, and thus to occasion the lightning passing from one cloud to another, or from a cloud into the earth.
This experiment of the chain and tankard is said to succeed as well with what is termed negative electricity in the theory of Dr. Franklin, as with what is termed positive electricity; but in that theory the negative electricity means a less quantity or total deprivation or vacuity of that fluid; now to condense negative electricity by lowering the suspended chain into the tankard ought to make it less negative; whereas in this experiment I am told it becomes more so, as appears by its stronger repulsion of cork balls suspended on silk strings, and previously electrised by rubbed sealing wax: and if the negative electricity be believed to be a perfect vacuum of it, the condensation of a vacuum of electricity is totally incomprehensible; and this experiment alone seems to demonstrate the existence of two electric ethers.
IX. Of Galvanic Electricity.
1. The conductors of electricity, as well as the nonconductors of it, have probably a portion of the vitreous and resinous ethers combined with them, and have also another portion of these ethers diffused round them, which forms their natural or spontaneous adhesive atmospheres; and which exists in different proportions round them correspondent in quantity to those which are combined with them, but opposite in kind.
These adhesive spontaneous atmospheres of electricity are shown to consist of different proportions or quantities of the electric ethers by Mr. Bennet's Doubler of Electricity, as mentioned in his work called New Experiments on Electricity, sold by Johnson. In this work, p. 91, the blade of a steel knife was evidently, in his language, positive, compared to a soft iron wire which was comparatively negative; so the adhesive electricity of gold, silver, copper, brass, bismuth, mercury, and various kinds of wood and stone, were what he terms positive or vitreous; and that of tin and zinc, what he terms negative or resinous.
Where these spontaneous atmospheres of diffused electricity surrounding two conducting bodies, as two pieces of silver, are perfectly similar, they probably do not intermix when brought into the vicinity of each other; but if these spontaneous atmospheres of diffused electricity are different in respect to the proportion of the two ethers, or perhaps in respect to their quantity, in however small degree either of these circumstances exists, they may be made to unite but with some difficulty; as the two metallic plates, suppose one of silver, and another of zinc, which they surround, must be brought into absolute or adhesive contact; or otherwise these atmospheres may be forced together so as to be much flattened, and compress each other where they meet, like small globules of quicksilver when pressed together, but without uniting.
This curious phenomenon may be seen in more dense electric atmospheres accumulated by art, as in the following experiment ascribed to Mr. Canton. Lay a wooden skewer the size of a goose-quill across a dry wine-glass, and another across another wine-glass; let the ends of them touch each other, as they lie in a horizontal line; call them X and Y; approach a rubbed glass-tube near the external end of the skewer X, but not so as to touch it; then separate the two skewers by removing the wine-glasses further from each other; and lastly, withdraw the rubbed glass-tube, and the skewer X will now be found to possess resinous electricity, which has been generally called negative or minus electricity; and the skewer Y will be found to possess vitreous, or what is generally termed positive or plus electricity.
The same phenomenon will occur if rubbed sealing wax be applied near to, but not in contact with, the skewer X, as the skewer X will then be left with an atmosphere of vitreous ether, and the skewer Y with one of resinous ether. These experiments also evince the existence of two electric fluids, as they cannot be understood from an idea of one being a greater or less quantity of the same material; as a vacuum of electric ether, brought near to one end of the skewer, cannot be conceived so to attract the ether as to produce a vacuum at the other end.
In this experiment the electric atmospheres, which are nearly of similar kinds, do not seem to touch, as there may remain a thin plate of air between them, in the same manner as small globules of mercury may be pressed together so as to compress each other, long before they intermix; or as plates of lead or brass require strongly to be pressed together before they acquire the attraction of cohesion; that is, before they come into real contact.
2. It is probable, that all bodies are more or less perfect conductors, as they have less or more of either of the electric ethers combined with them; as mentioned in Preliminary Proposition, No. VI. as they may then less resist the passage of either of the ethers through them. Whence some conducting bodies admit the junction of these spontaneous electric atmospheres, in which the proportions or quantities of the two ethers are not very different, with greater facility than others.
Thus in the common experiments, where the vitreous or resinous ether is accumulated by art, metallic bodies have been esteemed the best conductors, and next to these water, and all other moist bodies; but it was lately discovered, that dry charcoal, recently burnt, was a more perfect conductor than metals; and it appears from the experiments discovered by Galvani, which have thence the name of Galvanism, that animal flesh, and particularly perhaps the nerves of animals, both which are composed of much carbon and water, are the most perfect conductors yet discovered; that is, that they give the least resistance to the junction of the spontaneous electric atmospheres, which exist round metallic bodies, and which differ very little in respect to the proportions of their vitreous and resinous ingredients.
Thus also, though where the accumulated electricities are dense, as in charging a coated glass-jar, the glass, which intervenes, may be of considerable thickness, and may still become charged by the stronger attraction of the secondary electric ethers; but where the spontaneous adhesive electric atmospheres are employed to charge plates of air, as in the Galvanic pile, or probably to charge thin animal membranes or cuticles, as perhaps in the shock given by the torpedo or gymnotus, it seems necessary that the intervening nonconducting plate must be extremely thin, that it may become charged by the weaker attraction of these small quantities or difference of the spontaneous electric atmospheres; and in this circumstance only, I suppose, the shocks from the Galvanic pile, and from the torpedo and gymnotus, differ from those of the coated jar.
3. When atmospheres of electricity, which do not differ much in the quantity or proportion of their vitreous and resinous ethers, approach each other, they are not easily or rapidly united; but the predominant vitreous or resinous ether of one of them repels the similar ether of the opposed atmosphere, and attracts the contrary kind of ether.
The slowness or difficulty with, which atmospheres, which differ but little in kind or in density, unite with each other, appears not only from the experiment of Mr. Canton above related, but also from the repeated smaller shocks, which may be taken from a charged coated jar after the first or principal discharge, if the conducting medium has not been quickly removed, as is also mentioned above.
Hence those atmospheres of either kind of electric matter, which differ but very little from each other in kind or quantity, require the most perfect conductors to cause them to unite. Thus it appears by Mr. Bennet's doubler, as mentioned in the Preliminary Proposition, No. VI. that the natural adhesive atmosphere round silver contains more vitreous electricity than that naturally round zinc; but when thin plates of these metals, each about an ounce in weight, are laid on each other, or moderately pressed together, their atmospheres do not unite. For metallic plates, which when laid on each other, do not adhere, cannot be said to be in real contact, of which their not adhering is a proof; and in consequence a thin plate of air, or of their own repulsive ethers exists between them.
Hence when two plates of zinc and silver are thus brought in to the vicinity of each other, the plate of air between them, as they are not in adhesive contact, becomes like a charged coated jar; and if these two metallic plates are touched by your dry hands, they do not unite their electricities, as the dry cuticle is not a sufficiently good conductor; but if one of the metals be put above, and another under the tongue, the saliva and moist mucous membrane, muscular fibres, and nerves, supply so good a conductor, that this very minute electric shock is produced, and a kind of pungent taste is perceived.
When a plate or pencil of silver is put between the upper lip and the gum, and a plate or pencil of zinc under the tongue, a sensation of light is perceived in the eyes, as often as the exterior extremities of these metals are brought into contact; which is owing in like manner to the discharge of a very minute electric shock, which would not have been produced but by the intervention of such good conductors as moist membranes, muscular fibres, and nerves.
In this situation, a sensation of light is produced in the eyes; which seems to show, that these ethers pass through nerves more easily, than through muscular flesh simply; since the passage of them through the retina of the eyes from the upper gum to the parts beneath the tongue is a more distant one, than would otherwise appear necessary. It is not so easy to give the sensation of light in the eyes by passing a small shock of artificially accumulated electricity through, the eyes (though this may, I believe, be done) because this artificial accumulated electricity, as it passes with greater velocity than the spontaneous accumulations of it, will readily permeate the muscles or other moist parts of animal bodies; whereas the spontaneous accumulations of electricity seem to require the best of all conductors, as animal nerves, to facilitate their passage.
4. In the Galvanic pile of Volta this electric shock becomes so much increased, as to pass by less perfect conductors, and to give shocks to the arms of the conducting person, if the cuticle of his hands be moistened, and even to show sparks like the coated jar; which appears to be effected in this manner. When a plate of silver is laid horizontally on a plate of zinc, the plate of air between them becomes charged like a coated jar; as the silver, naturally possessing more vitreous electric ether, repels the vitreous ether, which the zinc possesses in less quantity, and attracts the resinous ether of the zinc. Whence the inferior surface of the plate of zinc abounds now with vitreous ether, and its upper surface with resinous ether. Beneath this pair of plates lay a cloth moistened with water, or with some better conductor, as salt and water, or a slight acid mixed with water, or volatile alcali of ammoniac mixed with water, and this vitreous electric ether on the lower surface of the zinc plate will be given to the second silver plate which lies beneath it; and thus this second silver plate will possess not only its own natural vitreous atmosphere, which was denser or in greater quantity than that of the zinc plate next beneath it, but now acquires an addition of vitreous ether from the zinc plate above it, conducted to it through the moist cloth.
This then will repel more vitreous ether from the second zinc plate into the third silver one; and so on till the plates of air between the zincs and silvers are all charged, and each stronger and stronger, as they descend in the pile.
If the reader still prefers the Franklinian theory of positive and negative electricity, he will please to put the word positive for vitreous, and negative for resinous, and he will find the theory of the Galvanic pile equally thus accounted for.
5. When a Galvanic pile is thus placed, and a communication between the two ends of it is made by wires, so that the electric shocks pass through water, the water becomes decomposed in some measure, and oxygen is liberated from it at the point of one wire, and hydrogen at the point of the other; and this though a syphon of water be interposed between them. This curious circumstance seems to evince the existence of two electric ethers, which enter the water at different ends of the syphon, and have chemical affinities to the component parts of it; the resinous ether sets at liberty the hydrogen at one end, and the vitreous ether the oxygen at the other end of the conducting medium.
Hence it must appear, that the longer the Galvanic pile, or the greater the number of the alternate pieces of silver and zinc that it consists of, the stronger will be the Galvanic shock; but there is another circumstance, difficult to explain, which is the perpetual decomposition of water by the Galvanic pile; when water is made the conducting medium between the two extremities of the pile.
As no conductors of electricity are absolutely perfect, there must be produced a certain accumulation of vitreous ether on one side of each charged plate of the Galvanic pile, and of resinous ether on the other side of it, before the discharge takes place, even though the conducting medium be in apparent contact. When the discharge does take place, the whole of the accumulated electricity explodes and vanishes; and then an instant of time is required for the silver and zinc again to attract from the air, or other bodies in their vicinity, their spontaneous natural atmospheres, and then another discharge ensues; and so repeatedly and perpetually till the surface of one of the metallic plates becomes so much oxydated or calcined, that it ceases to act.
Hence a perpetual motion may be said to be produced, with an incessant decomposition of water into the two gasses of oxygen and hydrogen; which must probably be constantly proceeding on all moist Surfaces, where a chain of electric conductors exists, surrounded with different proportions of the two electric ethers. Whence the ceaseless liberation of oxygen from the water has oxydated or calcined the ores of metals near the surface of the earth, as of manganese, of zinc into lapis calaminaris, of iron into various ochres, and other calciform ores. From this source also the corrosion of some metals may be traced, when they are immersed in water in the vicinity of each other, as when the copper sheathing of ships was held on by iron nails. And hence another great operation of nature is probably produced, I mean the restoration of oxygen to the atmosphere from the surface of the earth in dewy mornings, as well as from the perspiration of vegetable leaves; which atmospheric oxygen is hourly destructible by the respiration of animals and plants, by combustion, and by other oxydations.
6. The combination of the electric ethers with metallic bodies, before mentioned appears from the Galvanic pile; since, according to the experiments of Mr. Davy, when an acid is mixed with the water placed between the alternate pairs of silver and zinc plates, a much greater electric shock is produced by the same pile; and an anonymous writer in the Phil. Magaz. No. 36, for May 1801, asserts, that when the intervening cloths or papers are moistened with pure alcali, as a solution of pure ammonia, the effect is greater than by any other material. It must here be observed, that both the acid and the alcaline solution, or common salt and water, and even water alone, in these experiments much erodes the plates of zinc, and somewhat tarnishes those of silver. Whence it would appear, that as by the repeated explosions of the two electric ethers in the conducting water, both oxygen and hydrogen are liberated; the oxygen erodes the zinc plates, and thus increases the Galvanic shock by liberating their combined electric ethers: and that this erosion is much increased by a mixture either of acid or of volatile alcali with the water. Further experiments are wanting on this subject to show whether metallic bodies emit either or both of the electric ethers at the time of their solution or erosion in acids or in alcalies.
X. Of the two Magnetic Ethers.
1. Magnetism coincides with electricity in so many important points, that the existence of two magnetic ethers, as well as of two electric ones, becomes highly probable. We shall suppose, that in a common bar of iron or steel the two magnetic ethers exist intermixed or in their neutral state; which for the greater ease of speaking of them may be called arctic ether and antarctic ether; and in this state like the two electric fluids they are not cognizable by our senses of experiments.
When these two magnetic ethers are separated from each other, and the arctic ether is accumulated on one end of an iron or steel bar, which is then called the north pole of the magnet, and the antarctic ether is accumulated on the other end of the bar, and is then termed the south pole of the magnet; they become capable of attracting other pieces of iron or steel, and are thus cognizable by experiments.
It seems probable, that it is not the magnetic ether itself which attracts or repels particles of iron, but that an attractive and repulsive ether attends the magnetic ethers, as was shown to attend the electric ones in No. II. 9. of this Note; because magnetism does not pass through other bodies, as it does not escape from magnetised steel when in contact with other bodies; just as the electric fluids do not pass through glass, but the attractive and repellent ethers, which attend both the magnetic and electric ethers, pass through all bodies.
2. The prominent articles of analogical coincidence between magnetism and electricity are first, that when one end of an iron bar possesses an accumulation of arctic magnetic ether, or northern polarity; the other end possesses an accumulation of antarctic magnetic ether, or southern polarity; in the same manner as when vitreous electric ether is accumulated on one side of a coated glass jar, resinous electric ether becomes accumulated on the other side of it; as the vitreous and resinous ethers strongly attract each other, and strongly repel the ethers of the same denomination, but are prevented from intermixing by the glass plane between them; so the arctic and antarctic ethers attract each other, and repel those of similar denomination, but are prevented from intermixing by the iron or steel being a bad conductor of them; they will, nevertheless, sooner combine, when the bar is of soft iron, than when it is of hardened steel; and then they slowly combine without explosion, that is, without emitting heat and light like the electric ethers, and therefore resemble a mixture of oxygen and pure ammonia; which unite silently producing a neutral fluid without emitting any other fluids previously combined with them.
Secondly, If the north pole of a magnetic bar be approached near to the eye of a sewing needle, the arctic ether of the magnet attracts the antarctic ether, which resides in the needle towards the eye of it, and repels the arctic ether, which resides in the needle towards the point, precisely in the same manner as occurs in presenting an electrised, glass tube, or a rubbed stick of sealing wax to one extremity of two skewers insulated horizontally on wine-glasses in the experiment ascribed to Mr. Canton, and described in No. IX. 1, of this Additional Note, and also so exactly resembles the method of producing a separation and consequent accumulation of the two electric ethers by pressing a cushion on glass or on sealing wax, described in No. 4 of this Note, that their analogy is evidently apparent.
Thirdly, When much accumulated electricity is approached to one end of a long glass tube by a charged prime conductor, there will exist many divisions of the vitreous and resinous electricity alternately; as the vitreous ether attracts the resinous ether from a certain distance on the surface of the glass tube, and repels the vitreous ether; but, as this surface is a bad conductor, these reciprocal attractions and repulsions do not extend very far along it, but cease and recur in various parts of it. Exactly similar to this, when a magnetic bar is approximated to the end of a common bar of iron or steel, as described in Mr. Cavallo's valuable Treatise on Magnetism; the arctic ether of the north pole of the magnetic bar attracts the antarctic ether of the bar of common iron towards the end in contact, and repels the arctic ether; but, as iron and steel are as bad conductors of magnetism, as glass is of electricity, this accumulation of arctic ether extends but a little way, and then there exists an accumulation of antarctic ether; and thus reciprocally in three or four divisions of the bar, which now becomes magnetised, as the glass tube became electrised.
Another striking feature, which shows the sisterhood of electricity and magnetism, consists in the origin of both of them from the earth, or common mass of matter. The eduction of electricity from the earth is shown by an insulated cushion soon ceasing to supply either the vitreous or resinous ether to the whirling globe of glass or of sulphur; the eduction of magnetism from the earth appears from the following experiment: if a bar of iron be set upright on the earth in this part of the world, it becomes in a short time magnetical; the lower end possessing northern polarity, or arctic ether, and the higher end in consequence possessing southern polarity or antarctic ether; which may be well explained, if we suppose with Mr. Cavallo, that the earth itself is one great magnet, with its southern polarity or antarctic ether at the northern end of its axis; and, in consequence, that it attracts the arctic ether of the iron bar into that end of it which touches the earth, and repels the antarctic ether of the iron bar to the other end of it, exactly the same as when the southern pole of an artificial magnet is brought into contact with one end of a sewing needle.
3. The magnetic and electric ethers agree in the characters above mentioned, and perhaps in many others, but differ in the following ones. The electric ethers pass readily through metallic, aqueous, and carbonic bodies, but do not permeate vitreous or resinous ones; though on the surfaces of these they are capable of adhering, and of being accumulated by the approach or contact of other bodies; while the magnetic ethers will not permeate any bodies, and are capable of being accumulated only on iron and steel by the approach or contact of natural or artificial magnets, or of the earth; at the same time the attractive and repulsive powers both of the magnetic and electric ethers will act through all bodies, like those of gravitation and heat.
Secondly, The two electric ethers rush into combination, when they can approach each other, after having been separated and condensed, and produce a violent explosion emitting the heat and light, which were previously combined with them; whereas the two magnetic ethers slowly combine, after having been separated and accumulated on the opposite ends of a soft iron bar, and without emitting heat and light produce a neutral mixture, which, like the electric combination, ceases to be cognizable by our senses or experiments.
Thirdly, The wonderful property of the magnetic ethers, when separately accumulated on the ends of a needle, endeavouring to approach the two opposite poles of the earth; nothing similar to which has been observed in the electric ethers.
From these strict analogies between electricity and magnetism, we may conclude that the latter consists of two ethers as well as the former; and that they both, when separated by art or nature, combine by chemical affinity when they approach, the one exploding, and then consisting of a residuum after having emitted heat and light; and the other producing simply a neutralised fluid by their union.
1. When two fluids are diffused together without undergoing any change of their chemical properties, they are said simply to be mixed, and not combined; as milk and water when poured together, or as oxygen and azote in the common atmosphere. So when salt or sugar is diffused in water, it is termed solution, and not combination; as no change of their chemical properties succeeds.
But when an acid is mixed with a pure alcali a combination is produced, and the mixture is said to become neutral, as it does not possess the chemical properties which either of the two ingredients possessed in their separate state, and is therefore similar to neither of them. But when a carbonated alcali, as mild salt of tartar, is mixed with a mineral acid, they presently combine as above, but now the carbonic acid flies forcibly away in the form of gas; this, therefore, may be termed a kind of explosion, but cannot properly be so called, as the ethereal fluids of heat and light are not principally emitted, but an aerial one or gas; which may probably acquire a small quantity of heat from the combining matters.
But when strong acid of nitre is poured upon charcoal in fine powder, or upon oil of cloves, a violent explosion ensues, and the ethereal matters of heat and light are emitted in great abundance, and are dissipated; while in the former instance the oxygen of the nitrous acid unites with the carbone forming carbonic acid gas, and the azote escapes in its gaseous form; which may be termed a residuum after the explosion, and may be confined in a proper apparatus, which the heat and light cannot; for the former, if its production be great and sudden, bursts the vessels, or otherwise it passes slowly through them; and the latter passes through transparent bodies, and combines with opake ones.
But where ethers only are concerned in an explosion, as the two electric ones, which are previously difficult to confine in vessels; the repulsive ethers of heat and light are given out; and what remains is a combination of the two electric ethers; which in this state are attracted by all bodies, and form atmospheres round them.
These combined electric atmospheres must possess less heat and light after their explosion; which they seem afterwards to acquire at the time they are again separated from each other, probably from the combined heat and combined light of the cushion and glass, or of the cushion and resin; by the contact of which they are separated; and not from the diffused heat of them; but no experiments have yet been made to ascertain this fact, this combination of the vitreous and resinous ethers may be esteemed the residuum after their explosion.
2. Hence the essence of explosion consists in two bodies, which are previously united with heat and light, so strongly attracting each other, as to set at liberty those two repulsive ethers; but it happens, that these explosive materials cannot generally be brought into each other's vicinity in a state of sufficient density; unless they are also previously combined with some other material beside the light and heat above spoken of: as in the nitrous acid, the oxygen is previously combined with azote; and is thus in a condensed state, before it is brought into the contact or vicinity of the carbone; there are however bodies which will slowly explode; or give out heat and light, without being previously combined with other bodies; as phosphorus in the common atmosphere, some dead fish in a certain degree of putridity, and some living insects probably by their respiration in transparent lungs, which is a kind of combustion.
But the two electric ethers are condensed by being brought into vicinity with each other with a nonconductor between them; and thus explode, violently as soon as they communicate, either by rupturing the interposed nonconductor, or by a metallic communication. This curious method of a previous condensation of the two exploding matters, without either of them being combined with any other material except with the ethers of heat and light, distinguishes, this ethereal explosion from that of most other bodies; and seems to have been the cause, which prevented the ingenious Dr. Franklin, and others since his time, from ascribing the powerful effects of the electric battery, and of lightning in bursting trees, inflaming combustible materials, and fusing metals, to chemical explosion; which it resembles in every other circumstance, but in the manner of the previous condensation of the materials, so as violently to attract each other, and suddenly set at liberty the heat and light, with which one or both of them were combined.
3. This combination of vitreous and resinous electric ethers is again destroyed or weakened by the attractions of other bodies; as they separate intirely, or exist in different proportions, forming atmospheres round conducting and nonconducting bodies; and in this they resemble other combinations of matters; as oxygen and azote, when united in the production of nitrous acid, are again separated by carbone; which attracts the oxygen more powerfully, than that attracts the azote, with which it is combined.
This mode of again separating the combined electric ethers by pressing them, as they surround bodies in different proportions, into each other's atmospheres, as by the glass and cushion, has not been observed respecting the decomposition of other bodies; when their minute particles are brought so near together as to decompose each other; which has thence probably contributed to prevent this decomposition of the two combined electric ethers from being ascribed to chemical laws; but, as far as we know, the attractive and repulsive atmospheres round the minute particles of bodies in chemical operations may act in a similar manner; as the attractive and repulsive atmospheres, which accompany the electric ethers surrounding the larger masses of matter, and that hence both the electric and the chemical explosions are subject to the same laws, and also the decomposition again of those particles, which were combined in the act of explosion.
4. It is probable that this theory of electric and magnetic attractions and repulsions, which so visibly exist in atmospheres round larger masses of matter, may be applied to explain the invisible attractions and repulsions of the minute particles of bodies in chemical combinations and decompositions, and also to give a clear idea of the attractions of the great masses of matter, which form the gravitations of the universe.