I

THE POWER OF THE FUTURE.

would need a library, rather than a magazine sketch, to tell the monds" of the mine form the foundation on which the edifice of modern civilization is built. Not only do we owe to them the great sum of our industry, comfort, and luxury, but they are also an invaluable aid in the dissemination of literature, art, science, and education. Coal has not made better writers and thinkers, but it has made more numerous and practical ones, and by its cheapening of literature and development of wealth has vastly widened the reading and art-loving public. Morally, also, mankind has greatly advanced, through the breaking down of the barriers of distance and the mingling of the nations which we owe to coal. Our neighbor, whom we are commanded to love as ourselves, is no longer he who lives next door, but he who dwells beyond mountains and oceans. Coal, in short, has been invaluable to mankind, through the motive power which it yields, the vast increase in productiveness which we owe to it, and the rapidity with which it enables man to move himself and his goods over the surface of land and ocean.

Yet the deposits of coal are limited in quantity, and are being reduced with a wasteful rapidity which has already set engineers to calculating their probable duration. We are consuming in years what nature prepared by the slow work of centuries, and are "burning our candle at both ends" with a haste that will force the world of the future to look somewhere else for its supply of power.

The great prosperity of England we know to be due to the coal-beds which underlie that busy island. Yet those beds are being rapidly depleted, and recent calculations place the duration of the available beds, at the present growing rate of consumption, inside of two centuries. No such narrow limit of duration can be placed on the coal-supply of the United States and some other countries. There is an abundant stock of fuel for many generations to come, and this is added to by the petroleum and natural gas, whose output may last for centuries for all we positively know to the contrary.

We need not, therefore, concern ourselves about the fate of our immediate posterity. The edifice of civilization is safe for perhaps thousands of years; or at least it will not topple over through its foundations giving way. Yet that man will outlive coal seems almost beyond question. He has come upon the earth to stay for long future ages. And though the material interests of generations thousands of years in the time to come may have no living interest for us, we cannot help feeling some concern for that splendid edifice which man has built up with such busy labor and so many heart-throbs. Is it to fall again, and man swing back into that condition in which he existed when wood was his only fuel? Is all that we have so industriously worked for to become but the unsubstantial " pageant of a dream," and this era to be remembered in far-future centuries as the beginning of a glorious

"age of gold" which has been followed by a hard "age of iron"? or will man find new sources of power, and civilization continue to advance until it attains a height and splendor beyond our utmost conception?

There can be but one answer to this. Such sources of power are all around us. Some of them we are beginning to take hold of. Of others we are gaining vague glimpses. As long as the sun shines, civilization is safe. For this great life-giving orb is daily pouring upon the earth rivers of power that dwarf the rivulets which flow to us from our mines of coal,-stores grand, inexhaustible, endlessly available while the solar system remains in its present condition.

All we have we owe to the sun. Our wood, our coal, are solar gifts, bottled sunlight we may term them, stores of solid carbon extracted from the air by the solar beams. Yet all this represents but a trifling percentage of the power which the sun annually rains down upon the earth, nearly all of which escapes again into space, to be lost in its vast reaches. Is there no means by which a larger portion of this power can be made captive, and forced to turn our wheels, grind our corn, and weave our goods? This is one of the chief problems which man is now setting himself to solve.

The sunlight does more than to store up carbon in trees. It lifts water from the ocean and dashes it down upon the earth as rain. To it we owe the energy of the flowing streams. It sets the atmosphere in motion, producing the almost incessant winds. Here are two important sources of power, of both of which man has availed himself to some extent, but whose usefulness is capable of being greatly extended in the future. The irregularity of these sources of power, and the limited distribution of water-power, have stood in the way of their general use, as compared with the more manageable coal. Yet the energy they represent is enormous, and could it in any inexpensive way be stored when abundant for use during its times of scarcity, and be readily transported to centres of industry, it might become of the utmost service to man.

Recently experienced engineers have been earnestly endeavoring to make a more direct use of the power of the sunbeam. Their purpose has been to harness some of the light which is daily poured in profusion on a great part of the earth's surface, and set it to work to turn their machines. Several French engineers have experimented with these solar engines, as they are called, and with sufficient success to make them applicable for certain industrial purposes in Algeria. In 1882 one of these machines was tried in Paris, and with the power obtained a Marinoni press was run for several hours, printing five hundred copies per hour of a newspaper which was appropriately called the Sun Journal. During this time the sun was not very hot, and was frequently covered by clouds.

These French machines do not call for any description, as they have been surpassed in efficiency by the solar engine produced by John Ericsson, the eminent Swedish inventor, who recently died. For twenty-five years before his death Ericsson was actively engaged in experiments upon this machine, from which his experience taught him to look for valuable results. The trouble with the French machines, and the obstacles in the way of inventing an effective solar engine, he

perceived to be the great cost of large reflectors, the difficulty in obtaining accurate curvature in these reflectors, and the quick tarnishing of the polished surface, which needed much labor to keep it bright.

These difficulties he overcame by simple expedients, and laid the foundation of a cheap, permanent, and effective solar motor, whose character may be briefly described. The Ericsson machine, as at present constructed, consists of a rectangular trough which can be so rotated as constantly to receive the solar rays and reflect them upon a cylindrical heater which stands above its centre. This trough is formed of a light frame-work of wrought iron or steel, bent into a parabolic curve. Instead of lining this with a polished metal reflector, its concave surface is covered with plates of flat window-glass, silvered on the under-side, and so placed that each reflects the light that falls upon it to the heating cylinder. The glass is coated by a process which prevents the solar rays from destroying the silvering, as in ordinary mirrors. In this machine there is no difficulty about getting the curvature, and no need of repolishing, a feather duster doing all the cleaning necessary. The heater is exposed to a concentrated volume of solar rays sufficient to heat it to 600° Fahrenheit in ordinary sunshine. Either steam or heated air may be produced in this cylinder, and conducted through tubes to the engine, there to be employed in the moving of machinery.

In a paper published by Ericsson in 1884 he stated that with reflecting plates measuring one hundred and thirty by one hundred and eighty inches, and a steam cylinder measuring six by eight inches, he obtained an engine-speed of one hundred and twenty turns per minute, with an absolute pressure of thirty-five pounds per square inch on the working piston. He continued to labor on this machine until within two weeks of his death, and with almost his last words gave instructions to his chief engineer to go on with his projected improvements on the machine, and exacted his promise to do so.

The solar motor is yet in its infancy, but already gives promise of a vigorous maturity. Though it may always be of minor utility in the temperate zones of the earth, it is not easy to decide how great its future performance may become under the hot and long-continued solar rays of the tropics. Yet we can readily perceive that for the full utilization of such machines cheap and easy methods for the storing and carriage of energy will be required, as in the cases before considered.

The earth possesses still another source of energy, due, in this case, to the moon instead of the sun. It is the effect of the attraction of our sister orb on the ocean-waters of the earth. The daily tidal rise and fall of the waters represents an immense power, so great, indeed, that if only a minute fraction of it could be cheaply applied to man's uses we might calmly witness the vanishment of all our other machinerydriving powers. Some efforts have been made to utilize the tides in the moving of machinery, but the subject presents difficulties which have hitherto deterred engineers from actively pursuing it. That the lifting power of the water can be made to drive engines is unquestionable; but the successive rise and fall, with the intermediate intervals of rest, presents irregularities which stand seriously in the way of any steady application of tidal power.

The fact is, that before any of the sources of power mentioned can be fully utilized some method of storing the energy produced must be invented; and it is to this necessity that the attention of engineers is now most seriously turned. The power exists in unlimited abundance: how to use it cheaply and continuously, and transport it to the localities where wanted, is the problem to be solved.

There is no great difficulty in transporting power to small distances. During the excavation of the Mont Cenis Tunnel the machines which were boring into the heart of the mountain were driven by the water of small streams which ran down its surface. The water-power was used to compress air, which was carried in tubes to the drills, several miles away. Power may also be transported in the form of steam, while electric wires are capable of performing this service more rapidly and to much greater distances. In regard to conveyance of energy for long distances electricity presents the only readily available medium. It can be employed only very wastefully, its deliveries being much below its receipts. Yet when the power is very great, and transportation to a distant point very desirable, electricity may be usefully employed for this purpose. A few years ago it was seriously proposed to convey the water-power of Niagara Falls to New York in the shape of electricity and there reconvert it into engine-power. This and still greater achievements may yet be performed, when the capabilities of electricity are fully developed.

The methods by which power may be stored, to be given out again as required, next call for attention. This may be done in several ways, as in the coiling of springs and lifting of weights (methods applied in clocks and watches), and in the compression of air. But the most important and promising method of storing power at present is by the socalled electric accumulator, on which extensive experiments are being made. This is one of the most recent of ideas concerning the use of electricity, several years younger than the electric light or the telephone, -a mere scientific baby, in fact, yet giving decided indications of being a Hercules in the cradle.

What is known as stored electricity is simply an unstable chemical condition produced by the aid of electricity. To" store electricity," as at first performed, minium, or red lead,-a low oxide of lead,-was employed as the chemical agent. Two sheets of lead, coated with minium, were placed in a bath of acidulated water, and a current of electricity was sent through the combination. The effect was to remove the oxygen from the minium of one sheet and convey it to the other. Thus the minium on one sheet became converted into metallic lead, while that on the other became more highly oxidized. This is the first step of the An unstable chemical condition has been produced. The oxygen tends to leave the highly-oxidized sheet and return to the other. This proceeds rapidly if the two sheets are connected by an external wire. They then form a galvanic battery, and a current of electricity is produced, which flows through the wire and continues until both sheets are equally oxidized and the original condition is reproduced. This electrical current can be used to yield light, move machinery, or perform other mechanical labor. In this we have the whole story.

Wind, water, solar, tidal, or any other source of power may be used to yield the electricity for charging the battery, and the winds which buffet our houses on the outside may be used to light them within, hours after those winds have sunk to rest.

As yet, however, storage-batteries are far from perfect. Only about forty per cent. of the power put into them can be utilized. The chemical conditions change, and they lose their strength, even when not in use. These are defects which it will need much experiment to overcome. Many improvements have been made on the original Fauré accumulators, and they have been applied very successfully to yield stationary light and power, and less successfully for the running of street-cars. In the latter case their weight is against them, and the jarring of the car tends to lower the durability of the battery. What is wanted is a storage-battery with "good life, high efficiency, light weight, and convenient form for handling." "Then will come the era of swift, sure, safe, and pleasant surface-traffic." Yet when we consider that these "boxes of electricity," as Sir William Thomson called them, have been known for only about nine years, and that already great improvements have been made in them, it seems highly probable that the idea involved may be remarkably developed in the future, and our posterity be able to store up the power which is going to waste around them, in a cheap, convenient, durable, and easily-applied form, to be used when and where wanted.

We have here but hinted at what has been already done in the problem of replacing coal as our source of power. When we remember that it is but little more than a century since man began actively to study and apply the mechanical forces of nature, and that the bulk of his achievements have been performed within half a century, we may safely predict extraordinary progress in this direction in the coming centuries. Long before the mines of coal are exhausted it is probable that man will cease delving in the bowels of the earth for power, and will use the sun, the winds, the streams, the tides, and other agencies, to furnish him with an unlimited supply of mechanical energy.

Indeed, no one can guess what may be done in the future. We can dimly see possibilities which are as yet but the dreams of science. Electricity may be produced directly from the elements, instead of in the roundabout way in which we now obtain it. Other stores of power hidden in the elements may be set free, and put to work. Even the mysterious force concealed within the Keely motor, and striving, like an imprisoned giant, to break loose, may be chained down to useful work,-after a thousand or two more years of experiment. The extraordinary chemical force displayed in the explosion of dynamite gives us some feeble idea of what powers lie hidden within the chemical elements, and which yet may be taught to labor for the good of mankind. Inexhaustible stores of power exist all around us, useful now only for nature's interior operations, and openly visible only in their destructive outbreaks, which may yet be made useful in mechanical labors, and may lift man to an industrial eminence far beyond the utmost dreams of the present generation of mankind.

Charles Morris.