and the martial spirit, which were once the essentials of survival, whatever they may be to-day. The progress of change spreading upwards throughout society leads to some strange paradoxes. Official constructive philosophy long since deteriorated in a soil utterly exhausted by a monotonous alternation of introspective and retrospective agriculture and the bearing of a monotonous succession of the same dwindling harvest. It alone remains sterile, whilst all around, in the most unexpected places, the fertilising influence of the new knowledge, won and being won by the perfection of the extrospective or experimental method, is producing a luxuriant, if tangled, growth.

THE ENERGY OF COAL.

So far as the mere multiplication of the physical capacity of the race is concerned, the shifting and transport of loads, the hurling of projectiles or the minimisation of animal strength, the social effects of science are obvious enough. But these are but special instances of a universal change, which the modern doctrine of energy enables us to envisage in its entirety. All life-processes demand for their continuation and maintenance a continuous supply of energy, which is derived from food. A modern maxim might be, "Look after the energy and the matter will look after itself." In metabolism, so far as matter is concerned, there is a closed cycle. Men feed on animals, and animals on plants. The plants feed on the carbon-dioxide and other products of the animal metabolism, reconverting them into food. The net result is nil, or nearly so, as far as the material changes are concerned. They cancel out. But the one essential physical factor that makes the process possible is the supply of energy as sunlight

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to the plant, which, unlike the animal, can utilise it in this form for its life's work.

Scientifically there is nothing peculiar about vital energy, or about one form of available energy rather than another. That is to say, if not yet, some time in the future, the synthesis of food from the material constituents and any form of available energy will probably become possible. Historically, and till quite recently, the energy of sunlight, apart from an insignificant source in the tides, was the sole income of energy available for the world, and the traditional source by which, through the intermediary of plant metabolism, both men and animals lived. Mankind still lives solely on the energy derived from the sun, but in addition to his former income, utilised as before through the pursuit of agriculture, he has secured the control of a handsome legacy of solar energy, laid by in former times. He is living on an immensely more lavish scale than any of his predecessors, not because he has had any great increase in salary in the proper sense, not even because he is, in the mass, somewhat more intelligent, but because he is squandering an inheritance. The plants which, alone of living forms, can utilise the energy of sunlight, were at work for man ages before the remotest likeness to his image had appeared upon the world, and, even then, were laying the foundations on which alone his present greatness rests. Quite extraordinary physiographical conditions must have prevailed, an alternate uplifting and depressing of the bed of the ocean, time and again, as one age succeeded another, when the luxuriant forests of the carboniferous era flourished in the sun, and then sank beneath the sea. In this fossilised vegetation, preserved as coal, sandwiched between alternate layers of shale, is conserved some tiny fraction of the solar energy so prodigally radiated

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

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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