the investigation of which they have devoted their lives. They were and are obviously seekers of truth for the mere love of truth.

But the phenomena of nature are not dissociated in fact, however much we may attempt to localize and classify them. And so it chances that even the most visionary devotee of abstract science is forever being carried into fields of investigation trenching closely upon the practicalities of every-day life. A Black investigating the laws of heat is preparing the way explicitly, however unconsciously, for a Watt with his perfected mechanism of the steam engine.

Similarly a Davy working at the Royal Institution with his newly invented batteries, and intent on the discovery of new elements and the elucidation of new principles, is the direct forerunner of Jablochkoff, Brush, and Edison with their commercial revolution in the production of artificial light.

Again Oersted and Faraday, earnestly seeking out the fundamental facts as to the relations of electricity and magnetism, invent mechanisms which, though they seem but laboratory toys, are the direct forerunners of the modern dynamos that take so large a share in the world's work.

In a word, all along the line there is the closest association between what are commonly called the theoretical sciences and what with only partial propriety are termed the applied sciences. The linkage of one with the other must never be forgotten by anyone who would truly apprehend the status of those practical sciences which have revolutionized the civilization of the nineteenth and twentieth centuries in its most manifest aspects.

Nevertheless there is, to casual inspection, a somewhat radical distinction between theoretical and practical aspects of science—just as there are obvious differences between two sides of a shield. And as the theoretical aspects of science have largely claimed our attention hitherto, so its practical aspects will be explicitly put forward in the pages that follow. In the present volume we are concerned with those primitive applications of force through which man early learned to add to his working efficiency, and with the elaborate mechanisms—turbine wheels, steam engines, dynamos—through which he has been enabled to multiply his powers until it is scarcely exaggeration to say that he has made all Nature subservient to his will. It is this view which justifies the title of the volume, which might with equal propriety have been termed the Story of the World's Work.

THE CONQUEST OF NATURE

I

MAN AND NATURE

"Young men," said a wise physician in addressing a class of graduates in medicine, "you are about to enter the battle of life. Note that I say the 'battle' of life. Not a playground, but a battlefield is before you. It is a hard contest—a battle royal. Make no mistake as to that. Your studies here have furnished your equipment; now you must go forth each to fight for himself."

The same words might be said to every neophyte in whatever walk of life. The pursuit of every trade, every profession is a battle—a struggle for existence and for supremacy. Partly it is a battle against fellow men; partly against the contending powers of Nature. The physician meets rivalry from his brothers; but his chief battle is with disease. In the creative and manufacturing fields which will chiefly concern us in the following volumes, it is the powers of Nature that furnish an ever-present antagonism.

No stone can be lifted above another, to make the crudest wall or dwelling, but Nature—represented by her power of gravitation—strives at once to pull it down again. No structure is completed before the elements are at work defacing it, preparing its slow but certain ruin. Summer heat and winter cold expand and contract materials of every kind; rain and wind wear and warp and twist; the oxygen of the air gnaws into stone and iron alike;—in a word, all the elements are at work undoing what man has accomplished.

THE STRUGGLE FOR EXISTENCE

In the field of the agriculturist it is the same story. The earth which brings forth its crop of unwholesome weeds so bountifully, resists man's approaches when he strives to bring it under cultivation. Only by the most careful attention can useful grains be made to grow where the wildlings swarmed in profusion. Not only do wind and rain, blighting heat and withering cold menace the crops; but weeds invade the fields, the germs of fungoid pests lurk everywhere; and myriad insects attack orchard and meadow and grain field in devastating legions.

Similarly the beasts which were so rugged and resistant while in the wild state, become tender and susceptible to disease when made useful by domestication. Aforetime they roamed at large, braving every temperature and thriving in all weathers. But now they must be housed and cared for so tenderly that they become, as Thoreau said, the keepers of men, rather than kept by men, so much more independent are they than their alleged owners. Tender of constitution, domesticated beasts must be housed, to protect them from the blasts in which of yore their forebears revelled; and man must slave day in and day out to prepare food to meet the requirements of their pampered appetites.

He must struggle, too, to protect them from disease, and must care for them in time of illness as sedulously as he cares for his own kith and kin. Truly the ox is keeper of the man, and the seeming conquest that man has wrought has cost him dear.

But of course the story has another side. After all, Nature is not so malevolent as at first glance she seems. She has opposed man at every stage of his attempted progress; yet at the same time she has supplied him all his weapons for waging war upon her. Her great power of gravitation opposes every effort he makes; yet without that same power he could do nothing—he could not walk or stay upon the earth even; and no structure that he builds would hold in place for an instant.

So, too, the wind that smites him and tears at his handiwork, may be made to serve the purposes of turning his windmills and supplying him with power.

The water will serve a like purpose in turning his mills; and, changed to steam with the aid of Nature's store of coal, will make his steam engines and dynamos possible. Even the lightning he will harness and make subject to his will in the telegraphic currents and dynamos.

And in the fields, the grains which man struggles so arduously to produce are after all no thing of his creating. They are only adopted products of Nature, which he has striven to make serve his purpose by growing them under artificial conditions. So, too, the domesticated beasts are creatures that belong in the wilds and in distant lands. Man has brought them, in defiance of Nature, to uncongenial climes, and made them serve as workers and as food-suppliers where Nature alone could not support them. Turn loose the cow and the horse to forage for themselves here in the inhospitable north, and they would starve. They survive because man helps them to combat the adverse conditions imposed by Nature, yet no one of them could live for an hour were not the vital capacities supplied by Nature still in control.

Everywhere, then, it is the opposing of Nature, up to certain limits, with the aid of Nature's own tools, that constitutes man's work in the world. Just in proportion as he bends the elements to meet his needs, transforms the plants and animals, defies