Twentieth Century Inventions - A Forecast
by George Sutherland
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A Forecast




Twenty years ago the author started a career in technological journalism by writing descriptions of what he regarded as the most promising inventions which had been displayed in international exhibitions then recently held. From that time until the present it has been his constant duty and practice to take note of the advance of inventive science as applied to industrial improvement—to watch it as an organic growth, not only from a philosophical, but also from a practical, point of view. The advance towards the actual adoption of any great industrial invention is generally a more or less collective movement; and, in the course of a practice such as that referred to, the habit of watching the signs of progress has been naturally acquired.

Moreover, it has always been necessary to take a comprehensive, rather than a minute or detailed, view of the progress of the great industrial army of nineteenth century civilisation towards certain objectives. It is better, for some purposes of technological journalism, to be attached to the staff than to march with any individual company—for the war correspondent must ever place himself in a position from which a bird's-eye view is possible. The personal aspect of the campaign becomes merged in that which regards the army as an organic unit.

It may, therefore, be claimed that, in some moderate degree, the author is fitted by training and opportunities for undertaking the necessarily difficult task of foretelling the trend of invention and industrial improvement during the twentieth century. He must, of course, expect to be wrong in a certain proportion of his prognostications; but, like the meteorologists, he will be content if in a fair percentage of his forecasts it should be admitted that he has reasoned correctly according to the available data.

The questions to be answered in an inquiry as to the chances of failure or success which lie before any invention or proposed improvement are, first, whether it is really wanted; and, secondly, whether the environment in the midst of which it must make its debut is favourable. These requirements generally depend upon matters which, to a large extent, stand apart from the personal qualifications of any individual inventor.

In the course of a search through the vast accumulations of the patent specifications of various countries, the thought is almost irresistibly forced upon the mind of the investigator that "there is nothing new under the sun". No matter how far back he may push his inquiry in attempting to unveil the true source of any important idea, he will always find at some antecedent date the germ, either of the same inventive conception, or of something which is hardly distinguishable from it. The habit of research into the origin of improved industrial method must therefore help to strengthen the impression of the importance of gradual growth, and of general tendencies, as being the prime factors in promoting social advancement through the success of invention.

The same habit will also generally have the effect of rendering the searcher more diffident in any claims which he may entertain as to the originality of his own ideas. Inventive thought has been so enormously stimulated during the past two or three generations, that the public recognition of a want invariably sets thousands of minds thinking about the possible methods of ministering to it.

Startling illustrations of this fact are continually cropping up in the experiences of patent agents and others who are engaged in technological work and its literature. The average inventor is almost always inclined to imagine—when he finds another man working in exactly the same groove as himself—that by some means his ideas have leaked out, and have been pirated. But those who have studied invention, as a social and industrial force, know that nothing is more common than to find two or more inventors making entirely independent progress in the same direction.

For example, while this book was in course of preparation the author wrote out an account of an application of wireless telegraphy to the purpose of keeping all the clocks within a given area correct to one standard time. Within a few days there came to hand a copy of Engineering in which exactly the same suggestion was put forward, and an announcement was made to the effect that Mr. Richard Kerr, F.G.S., had been working independently on the same lines, the details of his method of applying the Hertzian waves to the purpose being practically the same as those sketched out by the author. This is only one of several instances of coincidences in independent work which have been noticed during the period while this volume was in course of preparation.

It may, therefore, be readily understood that the author would hardly like to undertake the task of attempting to discriminate between those forecasts in the subsequent pages which are the results of his own original suggestions, and those which have been derived from other sources. Whatever is of value has in all probability been thought of, or perhaps patented and otherwise publicly suggested, before. At any rate, the great majority of the forecasts are based on actual records of the trials of inventions which distinctly have a future lying before them in the years of the twentieth century.

In declining to enter into questions relating to the original authorship of the improvements or discoveries discussed, it should not be supposed that any wish is implied to detract from the merits of inventors and promoters of inventions, either individually or collectively. Many of these are the heroes and statesmen of that great nation which is gradually coming to be recognised as a true entity under the name of Civilisation. Their life's work is to elevate humanity, and if mankind paid more attention to them, and to what they are thinking and doing, instead of setting so much store by the veriest tittle-tattle of what is called political life, it would make much faster progress.

Some of the industrial improvements referred to in the succeeding pages are necessarily sketched in an indefinite manner. The outlines, as it were, have been only roughed in; and no attempt has been made to supply particulars, which in fact would be out of place in an essay towards a comprehensive survey in so small a space. It is upon the wise and skilful arrangement of details that sound and commercially profitable patents are usually founded, rather than upon the broad general principles of a proposed industrial advance or reform.

During the twentieth century this latter fact, already well recognised by experts in what is known as industrial property, will doubtless force itself more and more upon the attention of inventors. Every specification will require to be drawn up with the very greatest care in observing the truth taught by the fable of the boy and the jar of nuts. So rapidly does the mass of bygone patent records accumulate, that almost any kind of claim based upon very wide foundations will be found to have trenched upon ground already in some degree taken up.

Probably there is hardly anything indicated in this work which is not—in the strict sense of the rules laid down for examiners in those countries which make search as to originality—common public property. The labour involved in gathering the data for a forecast of the inventions likely to produce important effects during the twentieth century has been chiefly that of selecting from out of a vast mass of heterogeneous ideas those which give promise of springing up amidst favourable conditions and of growing to large proportions and bearing valuable fruit. Such ideas, when planted in the soil of the collective mind through the medium of official or other records, generally require for their germination a longer time than that for which the patent laws grant protection for industrial property. Many of them, indeed, have formed the subjects of patents which, from one reason or another, lapsed long before the expiration of the maximum terms. Nature is ever prodigal of seeds and of "seed-thoughts" but comparatively niggardly of places in which the young plant will find exactly the kind of soil, air, rain, and sunshine which the young plant needs.

If any one requires proof of this statement he will find ample evidence in support of it in the tenth chapter of Smiles's work on Industrial Biography, where facts and dates are adduced to show that steam locomotion, reaping machines, balloons, gunpowder, macadamised roads, coal gas, photography, anaesthesia, and even telegraphy are inventions which, so far as concerns the germ idea on which their success has been based, are of very much older origin than the world generally supposes. The author, therefore, submits that he is justified in referring inventions to the century in which they produce successful results, not to that in which they may have been first vaguely thought of. And in this view it is obvious that many of those patents and suggestions which have been published in current literature during the nineteenth century, but which, although pregnant with mighty industrial influences, have not yet reached fruition, are essentially inventions of the twentieth century. More than this, it is extremely probable that the great majority of those ideas which will move the industrial world during the next ensuing hundred years have already been indicated, more or less clearly, by the inventive thought of the nineteenth century.


December, 1900.


















The year 1801, the first of the nineteenth century, was annus mirabilis in the industrial history of mankind. It was in that year that the railway locomotive was invented by Richard Trevithick, who had studied the steam engine under a friend and assistant of James Watt. His patent, which was secured during the ensuing year, makes distinct mention of the use of his locomotive driven by steam upon tramways; and in 1803 he actually had an engine running on the Pen-y-Darran mining tramway in Cornwall. From that small beginning has grown a system of railway communication which has brought the farthest inland regions of mighty continents within easy reach of the seaboard and of the world's great markets; which has made social and friendly intercourse possible in millions of homes which otherwise would have been almost destitute of it; which has been the means of spreading a knowledge of literature, science and religion over the face of the civilised world; and which, at the present moment, constitutes the outward and visible sign of the difference between Western civilisation and that of the Asiatic, as seen in China.

In another corner of the globe, during the year 1801, Volta was constructing his first apparatus demonstrating the material and physical nature of those mysterious electric currents which his friend Professor Galvani of Bologna, who died just two years earlier, had at first ascribed to a physiological source. The researches of the latter, it will be remembered, were begun in an observation of the way in which the legs of a dead frog twitched under certain conditions. The voltaic pile was the first electric battery, and, therefore, the parent of the existing marvellous telegraphic and telephonic systems, while less immediately it led to the development of the dynamo and its work in electric lighting and traction. It brought into harmony much fragmentary knowledge which had lain disjointed in the armoury of the physicist since Dufay in France and Franklin in America had investigated their theories of positive and negative frictional electricities, and had connected them with the flash of lightning as seen in Nature. Thus it became a fresh starting point both for industry and for science.

At the Exposition of National Industry, held in Paris during the year 1801, a working model of the Jacquard loom was exhibited—the prototype of those remarkable pieces of mechanism by which the most elaborately figured designs are worked upon fabrics during the process of weaving by means of sets of perforated cardboards. This was the crowning achievement of the inventions relating to textile fabrics, which had rendered the latter half of the eighteenth century so noteworthy in an industrial sense. It brought artistic designs in articles of common use within the reach of even poor people, and has been the means of unconsciously improving the public taste, in matters of applied art, more rapidly than could have been accomplished by an army of trained artists. The riots in which the mob nearly drowned Jacquard at Lyons for attempting to set up some of his looms were very nearly a counterpart of those which had occurred in England in connection with the introduction of spinning, weaving and knitting machinery.

In Paris, during the first year of the nineteenth century, Robert Fulton, an American, and friend of the United States representative in France, was making trials on the Seine with his first steam-boat—a little vessel imitated by him later on in the first successful steamers which plied on the river Hudson, carrying passengers from New York. At the same time, William Symongton launched the Charlotte Dundas, the steam tug-boat which, on the Scottish canals, did the first actually useful work in the conveyance of goods by steam power on the water. These small experiments have initiated a movement in maritime transport which is fully comparable to that brought about on land by the invention of the railway locomotive.

Again, in 1801, Sir Humphry Davy gave his first lecture at the Royal Institution in London, where he had just been installed as a professor, and began that long series of investigations into the chemistry of common things which, taken up by his successor Faraday, gave to the United Kingdom the first start in some of those industries depending upon a knowledge of organic chemistry and the use of certain essential oils.

Public attention at the beginning of the nineteenth century, however, was directed anywhere but towards these small commencements of mighty forces which were to revolutionise the industrial world, and through it also the social and political. If in those days Cornwall was ever referred to, it was not by any means in connection with Trevithick and his steam-engine which would run on rails, but by way of reference to the relations of the Prince of Wales to the Duchy, and the proportion of its revenues which belonged to him from birth.

Glancing over the pages of any history compiled in the early half of the century, the eye will trace hardly the barest allusions to forces, the discoveries in which were, in the year 1801, still in the incipient stage. Canon Hughes, for instance, in his continuation of the histories of Hume and Smollett, devoted some forty pages to the record of that year. The space which he could spare from the demands made upon his attention by the wars in Spain and Egypt, and the naval conflict with France, was mainly occupied with such matters as the election of the Rev. Horne Tooke for Old Sarum, and the burning question as to whether that gentleman had not rendered himself permanently ineligible for Parliamentary honours through taking Holy Orders, and with a miscellaneous mass of topics relating to the merely evanescent politics of the day.

The whole of the effects of invention and discovery in making history during the first year of the century were dismissed by this writer with a casual reference to the augmentation of the productive power of the labouring population through the use of machinery, and a footnote stating that "this was more particularly the case in the cotton manufacture".

Time corrects the historical perspective of the past, but it does not very materially alter the power of the historical vision to adjust itself to an examination of the present day forces which are likely to grow to importance in the making of future history. When we ask what are the inventions and discoveries which are really destined to grow from seeds of the nineteenth into trees of the twentieth century, we are at once confronted with the same kind of difficulty which would present itself to one who, standing in the midst of an ancient forest, should be requested to indicate in what spots the wide-spreading giants of the next generation of trees might be expected to grow. The company promoter labels those inventions in which he is commercially interested as the affairs which will grow to huge dimensions in the future; while the man of scientific or mechanical bent is very apt to predict a mighty future only for achievements which strike him as being peculiarly brilliant.

Patent experts, on the other hand, when asked by their clients to state candidly what class of inventions may be relied upon to bring the most certain returns, generally reply that "big money usually comes from small patents". In other words, an invention embodying some comparatively trivial, but yet really serviceable, improvement on a very widely used type of machine; or a little bit of apparatus which in some small degree facilitates some well known process; or a fashionable toy or puzzle likely to have a good run for a season or two, and then a moderate sale for a few years longer; these are the things to be recommended to an inventor whose main object is to make money. Thus the most qualified experts in patent law and practice do not fail to disclose this fact to those who seek their professional advice in a money-making spirit, as the great majority of inventors do.

The full term of fourteen years in the United Kingdom, or seventeen in the United States, may be a ridiculously long period for which to grant a monopoly to the inventor of some ephemeral toy, although absolutely inadequate to secure the just reward for one who labours for many years to perfect an epoch-making invention, and then to introduce it to the public in the face of all the opposition from vested interests which such inventions almost invariably meet.

Thus the fact that a man has made money out of one class of patents may not be any safe guide at all to arriving at a due estimate of his ideas on industrial improvements of greater "pith and moment," but, on the contrary, it is generally exactly the reverse. The law offers an immense premium for such inventions as are readily introduced, and the inventor who has made it his business to take advantage of this fact is usually one of the last men from whom to get a trustworthy opinion on patents of a different class.

Of the patents taken out during the latter portion of the nineteenth century, many undoubtedly contain the germs of great ideas, and, nevertheless, have excited comparatively little attention from business men or from the general public. It was so in the latter part of the eighteenth century, and history is only repeating itself when the seeds of twentieth century industrial movements are permitted to germinate unseen.

For all practical purposes each invention must be referred to the age in which it actually does useful work in the service of mankind. Thus, Hero of Alexandria, in the third century B.C., devised a water fountain worked by the expansive power of steam. From time to time during the succeeding twenty centuries similar pieces of apparatus excited the curiosity of the inquisitive and the interest of the learned. The clever and eccentric Marquis of Worcester, in his little book published in 1663, A Century of the Names and Scantlings of Inventions, generally known as the Century of Inventions, gave an account of one application of the power of steam to lift water which he had worked out, probably on a scale large enough to have become of practical service. Thomas Savery and Denis Papin, both of them men of high attainments and great ingenuity, made important improvements before the end of the seventeenth century.

Yet, if we refer to the question as to the proper age to which the steam-engine as a useful invention is to be assigned, we shall unhesitatingly speak of it as an eighteenth century invention, and this notwithstanding the fact that Savery's patent for the first pumping engine which came into practical use was dated 1698. The real introduction of steam as a factor in man's daily work was effected later on, partly by Savery himself and partly by Newcomen, and above all by James Watt. The expiration of Watt's vital patent occurred in 1800, and he himself then retired from the active supervision of his engineering business, having virtually finished his great life's work on the last year of the century which he had marked for all time by the efforts of his genius.

Similarly we may confidently characterise the locomotive engine as an invention belonging to the first half of the nineteenth century, although tramways on the one hand, and steam-engines on the other hand, were ready for the application of steam transport, and the only work that remained to be accomplished in the half century indicated was the bringing of the two things together. The dynamo, as a factor in human life—or, in other words, the electric current as a form of energy producing power and light—is an invention of the second half of the nineteenth century, although the main principles upon which it was built were worked out prior to the year 1851.

It will be seen, in the course of the subsequent pages, that portable electric power has as yet won its way only into very up-to-date workshops and mines, and that the means by which it will be applied to numerous useful purposes in the field, the road, and the house will be distinctly inventions of the twentieth century. Similarly the steam-engine has not really been placed upon the ordinary road, although efforts have been made for more than a century to put it there, the conception of a road locomotive being, in fact, an earlier one than that of an engine running on rails. Steam automobiles and traction engines are still confined to special purposes, the natures of which prove that certain elements of adaptability are still lacking in order to render them universally useful as are the locomotive and the steam-ship.

In nearly every other important line of human needs and desires it will be found that merely tentative efforts have been made by ingenious minds resulting in inventions of greater or less promise. Many of the finest conceptions which have necessarily been set down as failures have missed fulfilling their intended missions, not so much by reason of inherent weakness, as through the want of accessory circumstances to assist them. As in biology, so in industrial progress the definition of fitness appended to the law of the survival of the fittest must have reference to the environment.

A foolish law or public prejudice results in the temporary failure of a great invention, and the inventor's patent succumbs to the inexorable operation of the struggle for existence. Yet, fortunately for mankind, if not for the individual inventor, an idea does not suffer extinction as the penalty for non-success in the struggle. "The beginning of creation," says Carlyle, "is light," and the kind of light which inventors throw upon the dark problems involving man's industrial progress is providentially indestructible.

Twentieth century inventions—as the term is used in this book—are, therefore, those which are destined to fulfil their missions during the ensuing hundred years. They are those whose light will not only exist in hidden places, but will also shine abroad to help and to bless mankind. Or, if we may revert to the former figure, they are those which have not only been planted in the seed and have germinated in the leaf, but which have grown to goodly proportions, so that none may dare to assert that they have been planted for nought. A man's age is the age in which he does his work rather than that in which he struggles to years of maturity. Moore and Byron were poets of the nineteenth century, although the one had attained to manhood and the other had grown from poverty to inherit a peerage before the new century dawned.

The prophetic role—although proverbially an unsafe one—is nevertheless one which every business man must play almost every day of his life. The merchant, the manufacturer, the publisher, the director, the manager, and even the artist, must perforce stake some portion of his success in life upon the chance of his forecast as to the success of a particular speculation, article of manufacture, or artistic conception, and its prospects of proving as attractive or remunerative as he has expected it to be. The successful business man no doubt makes his plans, as far as may be practicable, upon the system indicated by the humorist, who advises people never to prophesy unless they happen to know, but the nature of his knowledge is almost always to some extent removed from certainty. He may spend much time in laborious searching; make many inquiries from persons whom he believes to be competent to advise him; diligently study the conditions upon which the problem before him depends—in short, he may take every reasonable precaution against the chances of failure, yet, in spite of all, he must necessarily incur risks. And so it is with regard to the task of forecasting the trend of industrial improvement. All who are called upon to lay their plans for a number of years beforehand must necessarily be deeply interested in the problems relating to the various directions which the course of that improvement may possibly take. Meanwhile their estimates of the future, although based upon an intimate knowledge of the past and aided by naturally clear powers of insight, must be hypothetical and conditional. Unfortunately for the vast majority of manufacturing experts, the thoroughness with which they have mastered the details of one particular branch of industry too often blinds them to the chances of change arising from localities beyond their own restricted fields of vision.

The merriment occasioned by the first proposals for affixing pneumatic tyres to bicycles may be cited as a striking instance of the lack of forecasting insight displayed by very many of those who are best entitled to pronounce opinions on the minutiae of their particular avocations. In almost every "bike" shop and factory throughout the United Kingdom and America, the suggestion of putting an air-filled hosepipe around each wheel of the machine to act as a tyre was received with shouts of ridicule!

Railway men, who understood the wonderful elasticity imparted by air to pieces of mechanism, such as the pneumatic brake, were not by any means so much inclined to laughter; but naturally, for the most part, they deferred to the rule which enjoins every man to stick to his trade. The rule in question—when applied to the task of estimating the worth of inventions claiming to produce revolutionary effects in any industry—is necessarily, in the majority of cases, more or less irrelevant, because such an invention should be regarded not so much as a proposed innovation in an old trade as the creation of a new one.

George Stephenson's ideas on the transport of passengers and goods were almost unanimously condemned by the experts of his day who were engaged in that line of business. On points relating to wheels of waggons and the harness of horses, the opinions of these men were probably worth something; but in relation to steam locomotives, carriages and trucks running upon rails, their judgment was not merely worthless, but a good deal worse; it was indeed actually misleading, because based on a pretence of knowledge of a trade which was to be called into existence to compete with their own. "Great is Diana of the Ephesians" said the artificers of old; and on the strength of their expert knowledge in the making of idols they set themselves up as judges of systems of theology and morality. The argument, although based on self-interest subjectively, was nevertheless intended to carry weight even among persons who wished to judge the questions in dispute according to their merits, and most of the latter were only too ready to accept the implied dictum that men who work about a temple must be experts in theology! The principles upon which Royal Commissions and Select Committees are sometimes appointed and entrusted with the onerous duty of deciding upon far-reaching industrial problems, affecting the progress of trade and manufactures in the present day, involve exactly the same kind of fallacy. Men are selected to pronounce judgment upon the proposals of their rivals in trade, and narrow-minded specialists to give their opinions upon projects which essentially belong to the border lands between two or more branches of industry, and cannot be understood by persons not possessing a knowledge of both.

Yet the world's work goes on apace; and as capital is accumulated and seeks to find new outlets the multiplication of industrial projects must continue in spite of every discouragement. This process will go on at a rate even faster than that which was exhibited at the beginning of the nineteenth century; but in watching the course of advancement, the world must take count of ideas rather than of the names of those who may have claims to rank as the originators of ideas. While for purposes of convenience, history labels certain great inventive movements, each with the name of one pre-eminent individual who has contributed largely to its success, nothing like a due appraisement of the services rendered by other men is ever attempted. It is not even as if the commanding general should by public acclamation receive all the applause for a successful campaign to the exclusion of his lieutenants. The pioneers in each great department of invention have generally acted as forerunners of the men whose names have become the most famous. They have borne much of the heat and burden of the day, while their successors have reaped the fruits of triumph. Mr. Herbert Spencer's strong protest against the part assigned by some writers in the mental and industrial evolution of the human race to the influence of great men is certainly fully justified, if the attribute of greatness is to be ascribed only to those whose names figure in current histories. The parts performed by others, whose fate it may have been to have fallen into comparatively unfavourable environments, may have entitled them even more eminently to the acclamation of greatness.

The world in such a matter asks, reasonably enough under the circumstances, Shall we omit to honour any of the great men who have played important parts in an industrial movement, assigning as our motive the difficulty of enumerating so many names? For the encouragement of those to whom the ambition for fame acts as a great stimulus to self-devotion in the interests of human progress, it is unavoidable that some men should be singled out and made heroes, while the much more numerous class of those who have also done great work, but who have not been quite so successful, must pass out of the ken of all, excepting the few who possess an expert knowledge of the various subjects which they have taken in hand.

Still the distortion to which history has been subjected through its biographical mode of treatment must always be reckoned with as a factor of possible error by any one attempting to read the riddle of the past, and it may offer a still more dangerous snare to one who tries to deduce the future course of events from the evidences of the past, and the promises which they hold out. People are naturally prone to take it for granted that the world's progress during the first part of the twentieth century depends upon the future work of those inventors and industrial promoters whose names have become most famous during the latter half of the nineteenth. But this personal treatment of the subject will be found to be in the last degree unsatisfactory, when judged in the light both of past experience and of some of the utterances of those eminent inventors who have tried to forecast the future in their own particular lines of research.

If, therefore, we look at the whole subject from the entirely impersonal point of view, and face the task of forecasting the progress of industry during the twentieth century, in this aspect we shall find that we have entered upon a chapter in the evolution of the human race—dealing, in fact, with a branch of anthropology. We see certain industrial and inventive forces at work, producing certain initial effects, but plainly, as yet, falling immeasurably short of an entire fulfilment of their possibilities; setting to work a multitude of busy brains, planning and arranging, and gradually preparing the minds of the more apathetic portion of humanity for the reception of new ideas and the adoption of improved methods of life and of work. Whither is it all tending? Will the twentieth century bring about as great a change upon the earth—man's habitat—as the nineteenth did? Or have the possibilities of really great and effective industrial revolutions been practically exhausted? The belief impressed upon the Author's mind, by facts and considerations evoked during the collection of materials for this book, is that the march of industrial progress is only just beginning, and that the twentieth century will witness a far greater development than the nineteenth has seen.

The great majority of mankind still require to be released from the drudgery of irksome, physical exertion, which, when power has been cheapened, will be seen to be to a very large extent avoidable. Pleasurable exercise will be substituted for the monotonous, manual labour which, while it continues, generally precludes the possibility of mental improvement. Hygienic science will insist more strenuously than ever upon the great truth that, in order to be really serviceable in promoting the health of mind and body, physical exertion must be in some degree exhilarating, and the bad old practice of "all work and no play," which was based upon the assumption that a boy can get as much good out of chopping wood for an hour as out of a bicycle ride or a game of cricket, will be relegated to the limbo of exploded fallacies.

The race, as a whole, will be athletic in the same sense in which cultured ladies and gentlemen are at present. It will, a century hence, offer a still more striking contrast to the existing state of the Chinese, who bandage their women's feet in order to show that they are high born and never needed to walk or to exert themselves!—the assumption being that no one would ever move a muscle unless under fear of the lash of poverty or of actual hunger. The farther Western civilisation travels from that effete Eastern ideal, the greater will be the hope for human progress in physical, mental and moral well-being.



"Nature," remarked James Watt when he set to work inventing his improved steam-engine, "has always a weak side if we can only find it out." Many invaluable secrets have been successfully explored through the discovery of Nature's "weak side" since that momentous era in the industrial history of the world; and the nineteenth century, as Watt clearly foresaw, has been emphatically the age of steam power. In the condenser, the high pressure cylinder and the automatic cut-off, which utilises the expansive power of steam vapour, mankind now possesses the means of taming a monster whose capacities were almost entirely unknown to the ancients, and of bringing it into ready and willing service for the accomplishment of useful work. Vaguely and loosely it is often asserted that the age of steam is now giving place to that of electricity; but these two cannot yet be logically placed in opposition to one another. No method has yet been discovered whereby the heat of a furnace can be directly converted into an electric current. The steam-engine or, as Watt and his predecessors called it, the "fire-engine" is par excellence the world's prime motor; and by far the greater proportion of the electrical energy that is generated to-day owes its existence primarily to the steam-engine and to other forms of reciprocating machinery designed to utilise the expansive power of vapours or gases acting in a similar manner to steam.

The industrial revolutions of the coming century will, without doubt, be brought about very largely through the utilisation of Nature's waste energy in the service of mankind. Waterfalls, after being very largely neglected for two or three generations, are now commanding attention as valuable and highly profitable sources of power. This is only to be regarded as forming the small beginning of a movement which, in the coming century, will "acquire strength by going," and which most probably will, in less than a hundred years, have produced changes in the industrial world comparable to those brought about by the invention of the steam-engine.

Lord Kelvin, in the year 1881, briefly, but very significantly, classified the sources of power available to man under the five primary headings of tides, food, fuel, wind, and rain. Food is the generator of animal energy, fuel that of the power obtained from steam and other mechanical expansive engines; rain, as it falls on the hill-tops and descends in long lines of natural force to the sea coasts, furnishes power to the water-wheel; while wind may be utilised to generate mechanical energy through the agency of windmills and other contrivances. The tides as a source of useful power have hardly yet begun to make their influence felt, and indeed the possibility of largely using them is still a matter of doubt. The relative advantages of reclaiming a given area of soil for purposes of cultivation, and of converting the same land into a tidal basin in order to generate power through the inward and outward flow of the sea-water, were contrasted by Lord Kelvin in the statement of a problem as follows: Which is the more valuable—an agricultural area of forty acres or an available source of energy equal to one hundred horse-power? The data for the solution of such a question are obviously not at hand, unless the quality of the land, its relative nearness to the position at which power might be required, and several other factors in its economic application have been supplied. Still, the fact remains that very large quantities of the coastal land and a considerable quantity of expensive work would be needed for the generation, by means of the tides, of any really material quantity of power.

It is strange that, while so much has been written and spoken about the possibility of turning the energy of the tides to account for power in the service of man, comparatively little attention has been paid to the problem of similarly utilising the wave-power, which goes to waste in such inconceivably huge quantities. Where the tidal force elevates and depresses the sea-water on a shore, through a vertical distance of say eight feet, about once in twelve hours, the waves of the ocean will perform the same work during moderate weather once in every twelve or fifteen seconds. It is true that the moon in its attraction of the sea-water produces a vastly greater sum total of effect than the wind does in raising the surface-waves, but reckoning only that part of the ocean energy which might conceivably be made available for service it is safe to calculate that the waves offer between two and three thousand times as much opportunity for the capture of natural power and its application to useful work as the tides could ever present. In no other form is the energy of the wind brought forward in so small a compass or in so concrete a form. A steam-ship of 10,000 tons gross weight which rises and falls ten times per minute through an average height of 3.3 feet is thereby subjected to an influence equal to 22,400 horse-power. In this estimate the unit of the horse-power which has been adopted is Watt's arbitrary standard of "33,000 foot pounds per minute". The work done in raising the vessel referred to is equal to ten horse-power multiplied by the number of pounds in a ton, or, in other words, 22,400 horse-power, as stated.

Wind-power, again, has been to a large extent neglected since the advent of the steam-engine. The mightiest work carried out in any European country in the early part of the present century was that which the Dutch people most efficiently performed in the draining of their reclaimed land by means of scores of windmills erected along their seaboard. Even to the present day there are no examples of the direct employment of the power of the wind which can be placed in comparison with those still to be found on the coasts of Holland. But, unfortunately for the last generation of windmill builders, the intermittent character of the power to which they had to trust completely condemned it when placed in competition with the handy and always convenient steam-engine. The wind bloweth "where it listeth," but only at such times and seasons as it listeth, and its vagaries do not suit an employer whose wages list is mounting up whether he has his men fully occupied or not. The storage of power was the great thing needful to enable the windmill to hold its own. The electrical storage battery, compressed air, and other agencies which will be referred to later on, have now supplied this want of the windmill builder, but in the meantime his trade has been to a large extent destroyed. For its revival there is no doubt that, as Lord Kelvin remarked in the address already quoted, "the little thing wanted to let the thing be done is cheap windmills."

This, however, leads to another part of the problem. The costliness of the best modern patterns of windmill as now so extensively used, particularly in America, is mainly due to the elaborate, and, on the whole, successful attempts at minimising the objection of the intermittent nature of the source of power. To put the matter in another way, it may be said that lightness, and sensitiveness to the slightest breeze, have had to be conjoined with an eminent degree of safety in the severest gale, so that the most complicated self-regulating mechanisms have been rendered absolutely imperative. Once the principle of storage is applied, the whole of the conditions in this respect are revolutionised. There is no need to attempt the construction of wind-motors that shall run lightly in a soft zephyr of only five or six miles an hour, and stability is the main desideratum to be looked to.

The fixed windmill, which requires no swivel mechanism and no vane to keep it up to the wind, is the cheapest and may be made the most substantial of all the forms of wind-motor. In its rudimentary shape this very elementary windmill resembles a four-bladed screw steam-ship propeller. The wheel may be constructed by simply erecting a high windlass with arms bolted to the barrel at each end, making the shape of a rectangular cross. But those at one end are fixed in such positions that when viewed from the side they bisect the angles made by those at the other side. Sails of canvas or galvanised iron are then fastened to the arms, the position of which is such that the necessary obliquity to the line of the barrel is secured at once.

Looking at this elementary and at one time very popular form of windmill, and asking ourselves what adaptation its general principle is susceptible of in order that it may be usefully employed in conjunction with a storage battery, we find, at the outset, that, inasmuch as the electric generator requires a high speed, there is every inducement to greatly lengthen the barrel and at the same time to make the arms of the sails shorter, because short sails give in the windmill the high rate of speed required.

We are confronted, in fact, with the same kind of problem which met the constructors of turbine steam-engines designed for electric lighting. The object was to get an initial speed which would be so great as to admit of the coupling of the dynamo to the revolving shaft of the turbine steam-motor, without the employment of too much reducing gear. In the case of the wind-motor the eighteenth century miller was compelled to make the arms of his mill of gigantic length, so that, while the centre of the wind pressure on each arm was travelling at somewhere near to the rate of the wind, the axis would not be running too fast and the mill stones would never be grinding so rapidly as to "set the tems—or the lighter parts of the corn—on fire."

The dynamo for the generation of the electric current demands exactly the opposite class of conditions. We may therefore surmise that the windmill of the future, as constructed for the purposes of storing power, will have a long barrel upon which will be set numerous very short blades or sails. Reducing this again to its most convenient form, it is plain that a spiral of sheet-metal wound round the barrel will offer the most convenient type of structure for stability and cheapness combined. At the end of this long barrel will be fixed the dynamo, the armature of which is virtually a part of the barrel itself, while the magnets are placed in convenient positions on the supporting uprights. From the generating dynamo the current is conveyed directly to the storage batteries, and these alone work the electric motor, which, if desired, keeps continually in motion, pumping, grinding, or driving any suitable class of machinery.

It is rather surprising to find how relatively small is the advantage possessed by the vane-windmill over the fixed type in the matter of continuity of working. During about two years the Author conducted a series of experiments with the object of determining this point, the fixed windmill being applied to work which rendered it a matter of indifference in which way the wheel ran. With the prevailing winds from the west it ran in one direction, and with those of next degree of frequency, namely from the east, it turned in the reverse direction. The mill, however, was effective although the breeze might veer several points from either of the locations mentioned. It was found that there were rather less than one-fourth of the points of the compass, the winds from which would bring the wheel to a standstill or cause it to swing ineffectively, but as these were the directions in which the wind least frequently blew it might safely be reckoned that not one-eighth of the possible working hours of a swivel-windmill were really lost in the fixed machine.

With the type adapted to the working of a dynamo as already described, it will, in most cases, be convenient to construct two spirals on uprights set in three holes in the ground, forming lines at right angles to each other, but both engaging, by suitable gearing, with the electric current generator situated at the angle. This will be found cheaper than to go to the expense of constructing the mill on a swivel so that it may follow the direction of the wind. At the same time it should be noticed that the adoption of the high speed wind-wheel, consisting of some kind of spiral on a very long axis, may be made effective for improving even the swivel windmill itself, so as to adapt it for electric generation and conservation of power through the medium of the storage battery. Supposing that a number of small oblique sails be set upon an axis lying in the direction of the wind, the popular conception of the result of such an arrangement is that the foremost sails would render those behind it almost, if not entirely, useless.

The analogy followed in reaching this conclusion is that of the sails of a ship, but, as applied to wind-motors, it is quite misleading, because not more than one-third or one-fourth of the energy of the wind is expended upon the oblique sails of an ordinary wind-wheel. Moreover, in the case of a number of such wheels set on a long axis, one behind the other as described, the space within which the shelter of the front sail is operative to keep the wind from driving the next one is exceedingly minute.

The elasticity of the air and its frictional inertia when running in the form of wind cause the current to proceed on its course after a very slight check, which in point of time is momentary and in its effects almost infinitesimal. This being the case, and the principal expense attendant upon the construction of ordinary wind-engines being due to the need for providing a large diameter of wind-wheel, with all the attendant complications required to secure such a wheel from risk, it is obvious that as soon as the long axis and the very short sail, or the metallic spiral, have been generally introduced as adjuncts to the dynamo storage battery, an era of cheaper wind-motors will have been entered upon,—in fact, the "little want" of which Lord Kelvin spoke in 1881 will have been supplied. The high speed which the dynamo requires, and the more rapid rate at which windmills constructed on this very economical principle must necessarily run, both mark the two classes of apparatus as being eminently suited for mutual assistance in future usefulness.

The anemometer of the "Robinson" type, having four little hemispherical cups revolving horizontally, furnishes the first hint of another principle of construction adapted to the generation of electricity. Some years ago a professor in one of the Scottish Universities set up a windmill which was simply an amplified anemometer, and connected it with several of Faure's storage batteries for the purpose of furnishing the electric light to his residence. His report regarding his experience with this arrangement showed that the results of the system were quite satisfactory.

In this particular type of natural motor the wind-wheel, of course, is permanently set to run no matter from what direction the wind may be blowing. Tests instituted with the object of determining the pressure which the wind exerts on the cup of a "Robinson" anemometer have shown that when the breeze blows into the concave side of the cup, its effect is rather more than three times as strong as when it blows against the convex side. At any given time the principal part of the work done by a windmill constructed on this principle is being carried out by one cup which has its concave side presented to the wind, while, opposite to it, there is another cup travelling in the opposite direction to that of the wind but having its convex side opposed.

The facts that practically only one sail of the mill is operative at any given time, and that even the work which is done by this must be diminished by nearly one-third owing to the opposing "pull" of the cup at the opposite side, no doubt must detract from the merits of such a wind-motor, judged simply on the basis of actual area of sail employed. But when the matter of cost alone is taken as the standard, the advantages are much more evenly balanced than they might at first sight seem to be.

The cup-shaped sail may be greatly improved upon for power-generating purposes by adopting a sail having a section not semicircular but triangular in shape, and by extending its length in the vertical direction to a very considerable extent. Practically this cheap and efficient wind-motor then becomes a square or hexagonal upright axis of fairly large section, to each side of which is secured a board or a rigid sheet-metal sail projecting beyond the corners. The side of the axis and the projecting portion of the sail then together form the triangular section required.

For the sake of safety in time of storm, an opening may be left at the apex of the angle which is closed by a door kept shut through the tension of a spring. When the wind rises to such a speed as to overbalance the force of the spring each door opens and lets the blast pass through. One collateral advantage of this type of windmill is that it may be made to act virtually as its own stand, the only necessity in its erection being that it should have a collar fitting round the topmost bearing, which collar is fastened by four strong steel ropes to stakes securely set in the ground. The dynamo is then placed at the lower bearing and protected from the weather by a metal shield through which the shaft of the axis passes.

For pumping, and for other simple purposes apart from the use of the dynamo, a ready application of this form of wind-engine with a minimum of intricacy or expense may be worked out by setting the lower bearing in a round tank of water kept in circular motion by a set of small paddles working horizontally. Into the water a vertically-working paddle-wheel dips, carrying on its shaft a crank which directly drives the pump. This simple wind-motor is particularly safe in a storm, because on attaining a high speed it merely "smashes" the water in the tank.

Solar heat is one of the principal sources of the energy to be derived from the wind. Several very determined and ingenious attempts at the utilisation of the heat of sunshine for the driving of a motor have been made during the past century. As a solution of a mechanical and physical puzzle, the arrangement of a large reflector, with a small steam-boiler at the focus of the heat rays thrown by it, is full of interest. Yet, when a man like the late John Ericsson, who did so much to improve the caloric engine, and the steam-ship as applied to war-like purposes, meets with failure in the attempt to carry such an idea to a commercially successful issue, there is at least prima facie evidence of some obstacle which places the proposed machine at a disadvantage in competition with its rivals.

The solar engine, if generally introduced, would be found more intermittent in its action than the windmill—excepting perhaps in a very few localities where there is a cloudless sky throughout the year. The windmill gathers up the power generated by the expansion of the air in passing over long stretches of heated ground, while a solar engine cannot command more of the sun's heat than that which falls upon the reflector or condenser of the engine itself. The latter machine may possibly have a place assigned to it in the industrial economy of the future, but the sum total of the power which it will furnish must always be an insignificant fraction.

The wave-power machine, when allied to electric transmission, will, without doubt, supply in a cheap and convenient form a material proportion of the energy required during the twentieth century for industrial purposes. Easy and effective transmission is a sine qua non in this case, just as it is in the utilisation of waterfalls situated far from the busy mart and factory. Hardly any natural source of power presents so near an approach to constancy as the ocean billows. Shakespeare takes as his emblem of perpetual motion the dancing "waves o' th' sea".

But the ocean coasts—where alone natural wave-power is constant—are exactly the localities at which, as a rule, it is the least practicable to build up a manufacturing trade. Commerce needs smooth water for the havens offered to its ships, and inasmuch as this requirement is vastly more imperative during the early stages of civilisation than cheap power, the drift of manufacturing centres has been all towards the calm harbours and away from the ocean coasts. But electrical transmission in this connection abolishes space, and can bring to the service of man the power of the thundering wave just as it can that of the roaring torrent or waterfall.

The simplest form of wave-motor may be suggested by the force exerted by a ferry boat or dinghy tied up to a pier. The pull exerted by the rope is equal to the inertia of the boat as it falls into the trough of each wave successively, and the amount of strain involved in rough weather may be estimated from the thickness of the rope that is generally found necessary for the security of even very small craft indeed. A similar suggestion is conveyed by the need for elaborate "fenders" to break the force of the shock when a barge is lying alongside of a steamer, or when any other vessel is ranging along a pier or jetty.

A buoy of large size, moored in position at a convenient distance from a rock-bound ocean coast, will supply the first idea of a wave-motor on this primary principle as adapted for the generation of power. On the cliff a high derrick is erected. Over a pulley or wheel on the top of this there is passed a wire-rope cable fastened on the seaward side to the buoy, and on the landward side to the machinery in the engine-house. The whole arrangement in fact is very similar in appearance to the "poppet-head" and surface buildings that may be seen at any well-equipped mine. The difference in principle, of course, is that while on a mine the engine-house is supplying power to the other side of the derrick, the relations are reversed in the wave-motor, the energy being passed from the sea across into the engine-house. The reciprocating, or backward and forward, movement imparted to the cable by the rising and falling of the buoy now requires to be converted into a force exerted in one direction. In the steam-engine and in other machines of similar type, the problem is simplified by the uniform length of the stroke made by the piston, so that devices such as the crank and eccentric circular discs are readily applicable to the securing of a rotatory motion for a fly-wheel from a reciprocating motion in the cylinders. In the application of wave-power provision must be made for the utilisation of the force derived from movements of differing lengths, as well as of differing characters, in the force of impact. Every movement of the buoy which imparts motion to the pulley on top of the derrick must be converted into an additional impetus to a fly-wheel always running in the same direction.

The spur-wheel and ratchet, as at present largely used in machinery, offer a rough and ready means of solving this problem, but two very important improvements must be effected before full advantage can be taken of the principle involved. In the first place it is obvious that if a ratchet runs freely in one direction and only catches on the tooth of the spur-wheel when it is drawn in the other, the power developed and used is concentrated on one stroke, when it might, with greater advantage, be divided between the two; and in the second place the shock occasioned by the striking of the ratchet against the tooth when it just misses catching one of the teeth and is then forced along the whole length of the tooth gathering energy as it goes, must add greatly to the wear and tear of the machinery and to the unevenness of the running.

Taking the first of these difficulties into consideration it is obvious that by means of a counterbalancing weight, about equal to half that of the buoy, it is possible to cause the wave-power to operate two ratchets, one doing work when the pull is to landwards and the other when it is to seawards. Each, however, must be set to catch the teeth of its own separate spur-wheel; and, inasmuch as the direction of the motion in one case is different from what it is in the other, it is necessary that, by means of an intervening toothed wheel, the motion of one of these should be reversed before it is communicated to the fly-wheel. The latter is thus driven always in the same direction, both by the inward and by the outward stroke or pull of the cable from the buoy.

Perhaps the most convenient development of the system is that in which the spur-wheel is driven by two vertically pendant toothed bands, resembling saws, and of sufficient length to provide for the greatest possible amplitude of movement that could be imparted to them by the motion of the buoy. The teeth are set to engage in those of the spur-wheel, one band on each side, so that the effective stroke in one case is downward, while in the other it is upward. These toothed bands are drawn together at their lower ends by a spring, and they are also kept under downward tension by weights or a powerful spring beneath. The effect of this is that when both are drawn up and down the spur-wheel goes round with a continuous motion, because at every stroke the teeth of one band engage in the wheel and control it, while those of the reversed one (at the other side) slip quite freely.

The shock occasioned by the blow of the ratchet on the spur-wheel, or of one tooth upon another, may be reduced almost to vanishing point by multiplying the number of ratchets or toothed bands, and placing the effective ends, which engage in the teeth of the wheel successively, one very slightly in advance of the other. In this way the machine is so arranged that, no matter at what point the stroke imparted by the movement of the buoy may be arrested, there is always one or other of the ratchets or of the teeth which will fall into engagement with the tooth of the spur-wheel, very close to its effective face, and thus the momentum acquired by the one part before it impinges upon the other becomes comparatively small.

The limit to which it may be practicable to multiply ratchets or toothed bands will, of course, depend upon the thickness of the spur-wheel, and when this latter has been greatly enlarged, with the object of providing for this feature, it becomes virtually a steel drum having bevelled steps accurately cut longitudinally upon its periphery.

The masts of a ship tend to assume a position at right angles to the water-line. When the waves catch the vessel on the beam the greatest degree of pendulous swing is brought about in a series of waves so timed, and of such a length, that the duration of the swing coincides with the period required for one wave to succeed another. The increasing slope of the ship's decks, due to the inertia of this continuous rhythmical motion, often amounts to far more than the angle made by the declivity of the wave as compared with the sea level; and it is, of course, a source of serious danger in the eyes of the mariner.

But, for the purposes of the mechanician who desires to secure power from the waves, the problem is not how to avoid a pendulous motion but how to increase it. For each locality in which any large wave-power plant of machinery is to be installed, it will therefore be advisable to study the characteristic length of the wave, which, as observation has proved, is shorter in confined seas than in those fully open to the ocean. It is advisable then to make the beam width of the buoy, no matter how it may be turned, of such a length that when one side is well in the trough of a wave the other must be not far from the crest.

Practically the best design for such a floating power-generator will be one in which four buoys are placed, each of them at the end of one arm of a cross which has been braced up very firmly. From the angle of intersection projects a vertical mast, also firmly held by stays or guys. The whole must be anchored to the bottom of the sea by attachment to a large cemented block or other heavy weight having a ring let into it, from which is attached a chain of a few links connecting with an upright beam. It is the continuation of the latter above sea-level which forms the mast. On this beam the framework of the buoy must be free to move up and down.

At first sight it might seem as if this arrangement rendered nugatory the attempt to take advantage of the rise and fall of the buoy; but it is not so when the relations of the four buoys to one another are considered. Although the frame is free to move up and down upon the uprising shaft, still its inclination to the vertical is determined by the direction of the line drawn from a buoy in the trough of a wave to one on the crest. In order to facilitate the free movement, and to render the rocking effect more accurate and free from vibration, sets of wheels running on rails fixed to the beam are of considerable advantage.

The rise and fall of the tides render necessary the adoption of some such compensating device as that which has been indicated. Of course it would be possible to provide for utilising the force generated by a buoy simply moored direct to a ring at the bottom by means of a common chain cable; but this latter would require to be of a length sufficient to provide for the highest possible wave on the top of the highest tide. Then, again, the loose chain at low tide would permit the buoy to drift abroad within a very considerable area of sea surface, and in order to take advantage of the rise and fall on each wave it would be essential to provide at the derrick on the shore end of the wave-power plant very long toothed bands or equivalent devices on a similarly enlarged scale.

By providing three or four chains and moorings, meeting in a centre at the buoy itself but fastened to rings secured to weights at the bottom at a considerable distance apart, the lateral movement might, no doubt, be minimised; and for very simple installations this plan, associated with the device of taking a cable from the buoy and turning it several times round a drum on shore, could be used to furnish a convenient source of cheap power. The drum may carry a crank and shaft, which works the spur-wheel and toothed bands as already described, so that no matter at what stage in the revolution of the drum an upward or downward stroke may be stopped, the motion will still be communicated in a continuous rotary form to the fly-wheel.

But the beam and sliding frame, with buoys, give the best practical results, especially for large installations. It is in some instances advisable, especially where the depth of the water at a convenient distance from the shore is very considerable, not to provide a single beam reaching the whole distance to the bottom, but to anchor an air-tight tank below the surface and well beneath the depth at which wave disturbance is ever felt. From this submerged tank, which approximately keeps a steady position in all tides and weathers, the upward beam is attached by a ring just as would be done if the tank itself constituted the bottom.

One main reason for this arrangement is that the resistance of the beam to the water as it rocks backwards and forwards wastes to some extent the power generated by the force of the waves; and the greater the length of the beam, the longer must be the distance through which it has to travel when the buoys draw it into positions vertical to that of the framework. A thin steel pipe offers less resistance than a wooden beam of equal strength, besides facilitating the use of a simple device for enabling the frame and buoys to slide easily up and down.

The generally fatal defect of those inventions which have been designed in the past with the object of utilising wave-power has arisen from the mistake of placing too much of the machinery in the sea. The device of erecting in the water an adjustable reservoir to catch the wave crests and to use the power derived from them as the water escaped through a water-wheel was patented in 1869. Nearly twenty years later another scheme was brought out depending upon the working of a large pump fixed far under the surface, and connected with the shore so that, when operated by the rising and falling of floats upon the waves, it would drive a supply of water into an elevated reservoir on shore, from which, on escaping down the cliff, the pressure of the water would be utilised to work a turbine.

Earlier devices included the building of a mill upon a rocking barge, having weights and pulleys adjusted to run the machinery on board; and also a revolving float so constructed that each successive wave would turn one portion, but the latter would then be held firm by a toothed wheel and ratchet until another impulse would be given to it in the same direction. This plan included certain elements of the simple system already described; but it is obvious that some of its floating parts might with advantage have been removed to the shore end, where they would not only be available for ready inspection and adjustment, but also be out of harm's way in rough weather.

Different wave-lengths, as already explained, correspond to various periods in the pendulous swing of floating bodies. Examples have been cited by Mr. Vaughan Cornish, M. Sc., in Knowledge, 2nd March, 1896, as follows: "A wave-length of fifty feet corresponds to a period of two and a half seconds, while one of 310 feet corresponds to five and a half seconds. It is mentioned that the swing of the steam-ship Great Eastern took six seconds." Other authorities state that during a storm in the Atlantic the velocity of the wave was determined to be thirty-two miles an hour, and that nine or ten waves were included in each mile; thus about five would pass in each minute. But in average weather the number of waves to the mile is considerably larger, say, from fifteen to twenty to the mile; and in nearly calm days about double those numbers.

One interesting fact, which gives to wave-power a peculiarly enhanced value as a source of stored wind-power, is that the surface of the ocean—wild as it may at times appear—is not moved by such extremes of agitation as the atmosphere. In a calm it is never so inertly still, and in a storm it is never so far beyond the normal condition in its agitation as is the wind. The ocean surface to some extent operates as the governor of a steam-engine, checking an excess in either direction. In very moderate weather the number of waves to the mile is greatly increased, while their speed is not very much diminished. Indeed the rate at which they travel may even be increased.

This latter phenomenon generally occurs when long ocean rollers pass out of a region of high wind into one of relative calm, the energy remaining for a long time comparatively constant by reason of the multiplication of short, low waves created out of long, high ones. On all ocean coasts the normal condition of the surface is governed by this law, and it follows that, no matter what the local weather may be at any given time, there is always plenty of power available.

An attempt was made by M. C. Antoine, after a long series of observations, to establish a general relation between the speed of the wind and that of the waves caused by it, the formulae being published in the Revue Nautique et Coloniale in 1879. The rule may be taken as correct within certain limits, although in calm weather, when the condition of the ocean surface is almost entirely ruled by distant disturbances, it has but little relevancy. Approximately, the velocity of wave transmission is seven times the fourth root of the wind-speed; so that when the latter is a brisk breeze of sixteen miles an hour the waves will be travelling fourteen miles an hour, or very nearly as fast as the wind. When, on the other hand, a light breeze of nine miles an hour is driving the waves, the latter, according to the formula, should run about twelve and a half miles an hour; but, in point of fact, the influence of more distant commotion nearly always interferes with this result.

As a matter of experience, the waves on an ocean coast are usually running faster than the wind, and, being so much more numerous in calm than they are in rough weather, they maintain comparatively a uniform sum total of energy. It is obvious that, so far as practical purposes are concerned, three waves of an available height of three feet each are as effective as one of nine feet. If the state of the weather be such that the average wave length is 176 feet there will be exactly thirty waves to the mile, and if the speed be twelve miles an hour—that is to say, if an expanse of twelve miles of waves pass a given point hourly—then 360 waves will pass every sixty minutes, or six every minute. In the wave-power plant as described, each buoy of one hundred tons displacement when raised and depressed, say, three feet by every wave will thus be capable of giving power equal to three times 600, or 1,800 foot-tons per minute.

The unit of nominal horse-power being 33,000 foot-pounds or about fifteen foot-tons per minute, it is evident that each buoy, at its maximum, would be capable of giving about 120 horse-power. Supposing that half of the possible energy were exerted at the forward and half at the backward stroke and that each buoy were always in position to exert its full power upon the uprising shaft without deduction, the total effective duty of a machine such as has been described would be 480 horse-power. In practice, however, the available duty would probably, according to minor circumstances, be rather more or rather less than 300 horse-power.



The three principal forms of stored power which are now in sight above the horizon of the industrial outlook are the electric storage battery, compressed air, and calcium-carbide. The first of these has come largely into use owing to the demand for a regulated and stored supply of electricity available for lighting purposes. Indeed the storage battery has practically rendered safe the wide introduction of electric lighting, because a number of cells, when once charged, are always available as a reserve in case of any failure in the power or in the generators at any central station; and also because, by means of the storage cells or "accumulators," the amount of available electrical energy can be subdivided into different and subordinate circuits, thus obviating the necessity for the employment of currents of very high voltage and eluding the only imperfectly-solved problem of dividing a current traversing a wire as conveniently as lighting gas is divided by taking small pipes off from the gas mains.

Compressed air for the storage of power has hitherto been best appreciated in mining operations, one of the main reasons for this being that the liberated air itself—apart from the power which it conveyed and stored—has been so great a boon to the miner working in ill-ventilated stopes and drives. The cooling effects of the expansion, after close compression, are also very grateful to men labouring hard at very great depths, where the heat from the country rock would become, in the absence of such artificial refrigeration, almost overpowering. For underground railway traffic exactly the same recommendations have, at one period during the fourth quarter of the nineteenth century, given an adventitious stimulus to the use of compressed air.

Yet it is now undoubted that, even in deep mining, the engineer's best policy is to adopt different methods for the conveyance and storage of power on the one hand, and for the ventilation of the workings on the other. Few temptations are more illusory in the course of industrial progress than those presented by that class of inventions which aim at "killing two birds with one stone". If one object be successfully accomplished it almost invariably happens that the other is indifferently carried out; but the most frequent result is that both of them suffer in the attempt to adapt machinery to irreconcilable purposes.

The electric rock-drill is now winning its way into the mines which are ventilated with comparative ease as well as into those which are more difficult to supply with air. It is plain, therefore, that on its merits as a conveyer and storer of power the electric current is preferable to compressed air. The heat that is generated and then dissipated in the compression of any gas for such a purpose represents a very serious loss of power; and it is altogether an insufficient excuse to point to the compensation of coolness being secured from the expansion. Fans driven by electric motors already offer a better solution of the ventilation difficulty, and the advantages on this side are certain to increase rather than to diminish during the next few years.

The electric rock-drill, which can already hold its own with that driven by compressed air, is therefore bound to gain ground in the future. This is a type and indication of what will happen all along the industrial line, the electric current taking the place of the majority of other means adopted for the transmission of power. Even in workshops—where it is important to have a wide distribution of power and each man must be able to turn on a supply of it to his bench at any moment—shafting is being displaced by electric cables for the conveyance of power to numerous small motors.

The loss of power in this system has already been reduced to less than that which occurs with shafting, unless under the most favourable circumstances; and in places where the works are necessarily distributed over a considerable area the advantage is so pronounced that hardly any factories of that kind will be erected ten years hence without resort being had to electricity, and small motors as the means of distributing the requisite supplies of power to the spots where they are needed. It was a significant fact that at the Paris Exposition of 1900 the electric system of distribution was adopted.

In regard to compressed air, however, it seems practically certain that, notwithstanding its inferiority to electric storage of power, it is applicable to so many kinds of small and cheap installations that, on the whole, its area of usefulness, instead of being restricted, will be largely increased in the near future. There will be an advance all along the line; and although electric storage will far outstrip compressed air for the purposes of the large manufacturer, the air reservoir will prove highly useful in isolated situations, and particularly for agricultural work.

For example, as an adjunct to the ordinary rural windmill for pumping water, it will prove much more handy and effective than the system at present in vogue of keeping large tanks on hand for the purpose of ensuring a supply of water during periods of calm weather. Regarding a tank of water elevated above the ground and filled from a well as representing so much stored energy, and also comparing this with an equal bulk of air compressed to about 300 pounds pressure to the square inch, it would be easy to show that—unless the water has been pumped from a very deep well—the power which its elevation indicates must be only a small fraction of that enclosed in the air reservoir.

It will be one great point in favour of compressed air, as a form of stored energy for the special purpose of pumping, that by making a continuous small flow of air take the place of the water at the lowest level in the upward pipe, it is possible to cause it to do the pumping without the intervention of any motor.

One means of effecting this may be simply indicated. The air under pressure is admitted from a very small air pipe and the bubbles, as they rise, fill the hollow of an inverted iron cup rising and falling on a bearing like a hinge. Above and beneath the chamber containing this cup are valves opening upwards and similar to those of an ordinary force or suction pump. The cup must be weighted with adjustable weights so that it will not rise until quite full of air. When that point is reached the stroke is completed, the air having driven upwards a quantity of water of equal bulk with itself, and, as the cup falls again by its own weight, the vacuum caused by the air escaping upwards through the pipe is filled by an inrush of water through the lower valve. The function of the upper valve, at that time, is to keep the water in the pipe from falling when the pressure on the column is removed. The expansive power of the air enables it to do more lifting at the upper than at the lower level, so that a larger diameter of pipe can be used at the former place.

Cheap motors working on the same principle—that is to say through the upward escape of compressed air, gas or vapour filling a cup and operating it by its buoyancy, or turning a wheel in a similar manner—will doubtless be a feature in the machine work of the future; and for motors of this description it is obvious that compressed air will be very useful as the form of power-storage. Excepting under very special conditions, steam is not available for such a purpose, seeing that it condenses long before it has risen any material distance in a column of cold water.

"The present accumulator," remarked Prof. Sylvanus P. Thompson in the year 1881, referring to the Faure storage batteries then in use, "probably bears as much resemblance to the future accumulator as a glass bell-jar used in chemical experiments for holding gas does to the gasometer of a city gasworks, or James Watt's first model steam-engine does to the engines of an Atlantic steamer." When Faure, having in 1880 improved upon the storage battery of Plante, sent his four-cell battery from Paris to Glasgow, carrying in it stored electrical energy, it was found to contain power equal to close upon a million foot-pounds, which is about the work done by a horse-power during the space of half an hour. This battery weighed very nearly 75 lb. It nevertheless represented an immense forward step in the problem of compressing a given quantity of potential power into a small weight of accumulator.

The progress made during less than twenty years to the end of the century may be estimated from the conditions laid down by the Automobile Club of Paris for the competitive test of accumulators applicable to auto-car purposes in 1899. It was stipulated that five cells, weighing in all 244 lb., should give out 120 ampere-hours of electric intensity; and that at the conclusion of the test there should remain a voltage of 1.7 volt per cell.

Very great improvements in the construction of electric accumulators are to be looked for in the near future. Hitherto the average duration of the life of a storage cell has not been more than about two years; and where impurities have been present in the sulphuric acid, or in the litharge or "minium" employed, the term of durability has been still further shortened. It must be remembered that while the principal chemical and electrical action in the cell is a circular one,—that is to say, the plates and liquids get back to the original condition from which they started when beginning work in a given period,—there is also a progressive minor action depending upon the impurities that may be present. Such a reagent, for instance, as nitric acid has an extremely injurious effect upon the plates.

During the first decade after Plante and Faure had made their original discoveries, the main drawback to the advancement of the electric accumulator for the storage of power owed its existence to the lack of precise knowledge, among those placed in charge of storage batteries, as to the destructive effects of impurities in the cells. It is, however, now the rule that all acids and all samples of water used for the purpose must be carefully tested before adoption, and this practice, in itself, has greatly prolonged the average life of the accumulator cell.

The era of the large electric accumulator of the kind foreshadowed by Prof. Sylvanus P. Thompson has not yet arrived, the simple reason being that electric power storage—apart from the special purposes of the subdivision and transmission for lighting—has not yet been tried on a large scale. For the regulation and graduation of power it is exceedingly handy to be able to "switch-on" a number of small accumulator cells for any particular purpose; and, of course, the degree of control held in the hands of the engineer must depend largely on the smallness of each individual cell, and the number which he has at command. This fact of itself tends to keep down the size of the storage cell which is most popular.

But when power storage by means of the electric accumulator really begins in earnest the cells will attain to what would at present be regarded as mammoth proportions; and the special purpose aimed at in each instance of power installation will be the securing of continuity in the working of a machine depending upon some intermittent natural force. Windmills are especially marked out as the engines which will be used to put electrical energy into the accumulators. From these latter again the power will be given out and conveyed to a distance continuously.

High ridges and eminences of all kinds will in the future be selected as the sites of wind-power and accumulator plants. In the eighteenth century, when the corn from the wheat-field required to be ground into flour by the agency of wind-power, it was customary to build the mill on the top of some high hill and to cart all the material laboriously to the eminence. In the installations of the future the power will be brought to the material rather than the material to the power. From the ranges or mountain peaks, and also from smaller hills, will radiate electrical power-nerves branching out into network on the plains and supplying power for almost every purpose to which man applies physical force or electro-chemical energy.

The gas-engine during the twentieth century will vigorously dispute the field against electrical storage; and its success in the struggle—so far as regards its own particular province—will be enhanced owing to the fact that, in some respects, it will be able to command the services of electricity as its handmaid. Gas-engines are already very largely used as the actuators of electric lighting machinery. But in the developments which are now foreshadowed by the advent of acetylene gas the relation will be reversed. In other words, the gas-engine will owe its supply of cheap fuel to the electric current derived at small expense from natural sources of power.

Calcium carbide, by means of which acetylene gas is obtained as a product from water, becomes in this view stored power. The marvellously cheap "water-gas" which is made through a jet of steam impinging upon incandescent carbons or upon other suitable glowing hot materials will, no doubt, for a long time command the market after the date at which coal-gas for the generation of power has been partially superseded.

But it seems exceedingly probable that a compromise will ultimately be effected between the methods adopted for making water-gas and calcium carbide respectively, the electric current being employed to keep the carbons incandescent. When power is to be sold in concrete form it will be made up as calcium carbide, so that it can be conveyed to any place where it is required without the assistance of either pipes or wires. But when the laying of the latter is practicable—as it will be in the majority of instances—the gas for an engine will be obtainable without the need for forcing lime to combine with carbon as in calcium carbide.

Petroleum oil is estimated to supply power at just one-third the price of acetylene gas made with calcium carbide at a price of L20 per ton. This calculation was drawn up before the occurrence of the material rise in the price of "petrol" in the last year of the nineteenth century; while, concurrently, the price of calcium carbide was falling. A similar process will, on the average, be maintained throughout each decade; and, as larger plants, with cheaper natural sources of energy, are brought into requisition, the costs of power, as obtained from oil and from acetylene gas, will more and more closely approximate, until, in course of time, they will be about equal; after which, no doubt, the relative positions will be reversed, although not perhaps in the same ratio. Time is all on the side of the agent which depends for its cheapness of production on the utilisation of any natural source of power which is free of all cost save interest, wear and tear, and supervision.

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