throughout those bygone wastes of geological time. It is kindled, its store of energy bursts again into flame, and a civilisation, such as the world has never known, springs into being with the sunlight of a hundred million years ago augmenting its own.

The source of energy by which the modern world lives so profligately is no steady or perennial stream, such as that out of which our forefathers evolved their greatness. It is a stagnant pond, trapped from the main cosmical flow by a fortunate sequence of earth-movements, being drained at an ever-increasing rate and in an ever-increasing number of ways. "You have given me a store of energy," the modern Archimedes might say, "and steel wherewith to apply it, and lo! I have moved the world."

WATER POWER.

In justice to science, however, it must be said that not all its conquests are effected by the expenditure of the capital sum of energy; for there is a secondary, but considerable, source of energy available to the modern world, representing the better utilisation of the fixed income. Water power, or white fuel, as it is picturesquely called abroad, is a small part of the perennial supply of solar energy, conserved by purely physical processes, without the elaborate intervention of life at all, and the utilisation of which on every count, except the æsthetic, is a source of pure gain to the community. Energy itself is indestructible, and in itself is only valuable in its conversion from what may be called higher to lower forms. The natural transformations occur without loss of the absolute amount of energy. Rather what is lost is merely opportunity to direct those transformations to useful ends.

In nature this opportunity passes as

a rule

WATER POWER

13

quickly. Of the immense amount of radiant energy received by the earth, only a very minute proportion is arrested in its transformation. Most finds its way unused into the great ocean of heat energy of nearly uniform temperature, and the attainment of this dead level marks the final goal of every stream of energy received by or set in motion in the world, whether it is utilised or not. The opportunity once passed can never be retrieved. The energy now being considered formerly so ran to waste. Now it, to a great extent, turns turbines linked to dynamos, feeds the fires of electric furnaces at temperatures rivalled only by the originating sun, links itself to matter in the form of compounds, which are used to fertilise the soil and facilitate the work of sunlight and the seed, producing food. The food nourishes an army of workers, and the energy of the falling waterdrops, arrested in their headlong passage to the sea, now pursues a long eventful journey, beyond even the ken of the cold calculations of science. Linked in intimacy with human destiny, it translates thought and intelligence into action, before the partnership is severed, and it merges itself at last into the general level it set out so bravely to reach, headlong and divinely useless at one bound. Science that has done this has moved the whole world nearer to the glow. Not at its door, surely, should be laid the consequences if the energy of the falling waterdrops has been drained to provide the machinery of destruction, rather than of life.

THE SOURCE OF COSMICAL ENERGY.

Until the twentieth century had entered its opening decade a thoughtful observer of the social consequences of science would have seen in the revolution cause for profound uneasiness. Here was

no stable or enduring development, but rather the

D

accelerating progress of the spendthrift to destruction, so soon as the inheritance had been squandered and the inevitable day of reckoning arrived. When coal and oil were exhausted, and the daily modicum of sunlight represented once again, as of yore, the whole precarious means of livelihood of the world, the new inanimate servant of science, like the slaves of the ancients, would prove a dangerous helpmate, and the mushroom civilisation it had engendered would dissolve like the historic empires of the past, this time submerging the world.

No one had guessed the truth, though geological records tell of a history, vastly longer than human, during which, without much change, certainly without any evidence of progressive exhaustion, the energy of the sun had been invigorating and quickening the world. The fixed stars overhead, shining without apparent change of splendour throughout the past ages so far back as human memory extends, speak of a continuous outpouring of energy which, making all allowance for the vast scale of cosmical events, possesses a character of permanence and endurance foreign to the processes and events which hitherto had come within the ken of science. No one had guessed the original source of the stream of energy which rejuvenates the universe, nor that it has its rise, not in the unfathomable immensities of space, but in the individual atoms of matter all around. In so far as it is dominated by the supply of available energy, the limits of the possible expansion and development of the race in the future have been virtually abolished by this discovery of the immanence of the physical sources of life and motion in the universe.

Painfully and with infinite slowness man has crawled to the elevation from which he can envisage his eventful past as a whole from one standpoint, as

THE SOURCE OF COSMICAL ENERGY

15

that of a struggle, still largely internecine rather than co-operative, for a miserably inadequate allowance of energy. He looks back across the gulf of time from the day of the nameless and forgotten savage, who first discovered the art of kindling a fire, to himself, his logical descendant, master of a world largely nourished by the energy of fuel, and humming with the music of inanimate machinery. He turns his thoughts downward into the earth and wonders how long the source of his new life will hold out. He looks up once more at the unchanging stars and realises, as one who before has been but blind, that the immeasurable interval that separates him from the hidden sources which bear the universe along, is no immeasurable interval of space, whatever it may be of future time. The main stream sweeps past his doors, and the great gulf that yawns between him and the consummation of his emancipation looks small enough compared with the gulf that yawns behind.

No better illustration could be chosen of the spirit of absolute detachment from practical affairs, in which the highest and most practical knowledge is won, than the familiar history of the march of events which, in the closing decade of the nineteenth century and the opening years of the twentieth, revealed the immanence and accessibility of cosmical energy. To spend a feverish life in the attempt to transmute base-metal into gold, or to discover the secret of perpetual motion, would be to tread a well-trodden highway leading nowhere. But to exhibit a divine curiosity in an abstruse phenomenon, such as the rays given out by fluorescent substances, and whether any of them, like the X-rays, are able to penetrate an opaque material, to follow nature rather than to lead, and to win a grain of knowledge for the communism of science, is to stumble upon secrets such as these

unawares.

So radium was discovered, and it has been remarked that the future race will date the coming in of its kingdom from this discovery, mainly due to

a woman.

Through the wealth of new discovery that followed the recognition and investigation of natural radioactivity, we have but to pursue still the single connected thread which science has shot through the whole fabric of human history. Rays of a fundamentally new character are given out by radium, of various kinds and intense interest, and a thousand new phenomena make themselves manifest, but like galley slaves and fertilisers, waterfalls and food, they must here be brought into line from the single view point. Their energy is of the same category and obeys the same laws as the forms which before have nourished and embellished life. Not yet, at least, has science got outside the jurisdiction of that universal legislation, whatever may be its ultimate aspirations.

The energy evolved by radium spontaneously, however new and wonderful it may be, is yet measurable in current coin. In a single day it approaches in magnitude the energy evolved from a similar weight of any materials undergoing the most energetic chemical reactions known. In a year it evolves about 150 times as much energy as would be evolved in the complete combustion of the same weight of coal. Yet in the fifteen years that have elapsed since the discovery no measurable diminution of this rate of emission has been observed. If science is right, this emission will steadily decrease as the centuries roll by. But it is still possible to put a value on the total amount of energy a given weight of radium will furnish before the outflow comes to an end. It is about a third of a million times as great as would be evolved in the