experience for the last three thousand years as an argument against the probability of such occurrences in past ages; but it is not pretended that such a combination can be foreseen.

In speculating on catastrophes by water, we may certainly anticipate great floods in future, and we may therefore presume that they have happened again and again in past times. The existence of enormous seas of fresh water such as the North American lakes, the largest of which is elevated more than six hundred feet above the level of the ocean, and is in parts twelve hundred feet deep, is alone sufficient to assure us, that the time will come, however distant, when a deluge will lay waste a considerable part of the American continent. No hypothetical agency is required to cause the sudden escape of the confined waters. Such changes of level, and opening of fissures, as have accompanied earthquakes since the commencement of the present century, or such excavation of ravines as the receding cataract of Niagara is now effecting, might breach the barriers. Notwithstanding, therefore, that we have not witnessed within the last three thousand years the devastation by deluge of a large continent, yet, as we may predict the future occurrence of such catastrophes, we are authorized to regard them as part of the present order of Nature, and they may be introduced into geological speculations respecting the past, provided we do not imagine them to have been more frequent or general than we expect them to be in time to come.

The great contrast in the aspect of the older and newer rocks, in their texture, structure, and in the derangement of the strata, appeared formerly one of the strongest grounds for presuming that the causes to which they owed their origin were perfectly dissimilar from those now in operation. But this incongruity may now be regarded as the natural result of subsequent modifications, since the difference of the relative age is demonstrated to have been so immense, that, however slow and insensible the change, it must have become important in the course of so many ages. In addition to the volcanic heat, to which the Vulcanists formerly attributed too much influence, we must allow for the effect of mechanical pressure, of chemical affinity, of percolation by mineral waters, of permeation by elastic fluids, and the action, perhaps, of many other forces less understood, such as electricity and magnetism. In regard to the signs of upraising and sinking, of fracture and contortion in rocks, it is evident that newer strata cannot be shaken by earthquakes, unless the sub

jacent rocks are also affected; so that the contrast in the relative degree of disturbance in the more ancient and the newer strata, is one of many proofs that the convulsions have happened in different eras, and the fact confirms the uniformity of the action of subterranean forces, instead of their greater violence in the primeval ages.

The science of Geology is enormously indebted to Lyell—more so, as I believe, than to any other man who ever lived. — Darwin. Autobiography.

Pour juger de ce qui est arrivé, et même de ce qui arrivera, nous n'avons qu'à examiner ce qui arrive. - Buffon. Théorie de la Terre.

I. SOME INVENTIONS OF THE EIGHTEENTH AND NINETEENTH CENTURIES. APPLIED SCIENCE AND ENGINEERING

He who seeks for immediate practical use in the pursuit of science, may be reasonably sure that he will seek in vain. Complete knowledge and complete understanding of the action of the forces of nature and of the mind, is the only thing that science can aim at. The individual investigator must find his reward in the joy of new discoveries. . . in the consciousness of having contributed to the growing capital of knowledge. . . . Who could have imagined, when Galvani observed the twitching of the frog muscles as he brought various metals in contact with them, that eighty years later Europe would be overspun with wires which transmit messages from Madrid to St. Petersburg with the rapidity of lightning, by means of the same principle whose first manifestations this anatomist then observed. — Helmholtz.

The place of inventions in the history of science is hard to define. Conditioned as they doubtless are by a favorable environment — at least for survival - they do not always obviously arise as a direct or logical consequence of preceding discoveries, or even of known principles, but seem sometimes to spring almost de novo from the brain of the inventor. And yet such an origin is probably more apparent than real. The steam-engine could hardly have come from Watt without Newcomen and Black as his predecessors, the telegraph from Morse or the telephone from Bell except after Franklin, Oersted and Faraday. Probably the truth is that if we only knew all the facts, instead of only some of them, we should find every invention the natural descendant, near or remote, of science already existing. And as inheritance often seems to skip a generation or two and children

sometimes show no discoverable resemblance to their immediate forbears, so inventions may come without disclosing any resemblance to parent inventions or ideas, while yet really intimately related to knowledge that has gone before.

Nor is it easy to estimate the reciprocal debt of science to inventions and the arts. That this debt is large there can be no doubt. To illustrate this fact it is hardly necessary to do more than mention examples, such as the service of the compass to the sciences of geography, navigation and surveying; of the telescope and the chronometer to astronomy; of the microscope to biology; of the air pump to natural philosophy; or of the abacus or the Arabic numerals to arithmetic.

Among the more notable of the inventions of the nineteenth century were the locomotive, the steamboat, the friction match, the sewing-machine, the steel pen, the telegraph, the telephone and the phonograph; labor-saving machinery; explosives; and the internal combustion engine, with its numerous offspring (motor vehicles, airplanes, motor boats, etc.).

POWER: ITS SOURCES AND SIGNIFICANCE.

The recent progress

of science and of civilization has been accompanied by a remarkable extension of man's control over his environment, which has come largely with his ability to develop, transmit, and utilize chemical, gravitational and electrical energy or power. The ancients and the men of the Middle Ages used chiefly the power of man and other animals and of winds (windmills) and to some extent water (i.e. gravitation), as in water-wheels, but knew little of heat power or chemical power and nothing of electrical power, or of power transmission of any kind, except in moving herds, treadmills, or marching armies.

In past times the chief store of national power was manual labor: to-day it is the machine that does the work.-K. Pearson.

The first step in the modern direction was apparently toward chemical power, in the invention of gunpowder.

GUNPOWDER, NITROGLYCERINE, DYNAMITE. Gunpowder is believed to have been known to the Chinese long belong it appeared in Europe. An explosive mixture of charcoal, sulphur, and nitre was apparently also known to the Arabians, but the first important appearance of gunpowder in Europe was about the fourteenth century, and since the sixteenth it has played an all-important part in

war and in peace. Its effects upon society and civilization have been profound, and with society and civilization the progress of science is always closely bound up.

The manufacture of gunpowder marks the beginning of the manufacture of power, if we may describe the controlled accumulation, storage and liberation of energy by that convenient term. In 1845 gun-cotton was invented by Schönbein, and in 1847 nitroglycerine by Sobrero, and both explosives were found to be far more copious and powerful sources of energy than gunpowder. It was Alfred Nobel, however, a Swedish engineer, who after mixing nitroglycerine with gunpowder first made practical use of this for blasting. It was also Nobel who in 1867 made nitroglycerine less dangerous by diluting it with inert substances such as silicious earth, mixtures to which he gave the name dynamite.1

The manufacture of power from gravitational sources, such as water-power and wind power, goes back to the earliest timessails, wind-mills and water-wheels being of very ancient origin. Power from fuel begins with Newcomen, Watt and the steamengine. Electrical power is at present chiefly derived indirectly from gravitational (hydraulic) or from chemical (fuel) sources.

THE STEAM-ENGINE.-The last half of the eighteenth century was not merely an era of great revolutions: it was also an age of great inventions and among these, first in importance as well as first to arise, was the steam-engine.

Various and more or less successful attempts to utilize heat or steam as a source of power had been made before Watt's time, such, for example, as those of Hero in Alexandria (120 B.C.) the Marquis of Worcester (1663) and Newcomen (1705). Of these only Newcomen's need be dwelt upon here. In Newcomen's engine a vertical cylinder with piston was used, the piston-rod, also vertical, being fixed above to one end of a walking-beam of which the other end carried a parallel rod. Thus the rise and fall of the piston caused a corresponding fall and rise of a parallel rod, which could be attached to anything, e.g. to a pump. The cylinder was connected with a steam

1 Nobel died in 1896, bequeathing his fortune, estimated at $9,000,000, to the founding of a fund which supports the international "prizes"-usually $40,000 each which bear his name and are annually awarded to those who have most contributed to "the good of humanity." Five prizes have been usually given: viz. one in physics, one in chemistry, one in medicine or physiology, one in literature and one for the promotion of peace.

boiler by a pipe fitted with a stopcock, and was filled with steam below the piston by opening the stopcock. The steam pressing upon the boiler raised the piston and depressed the parallel (pump) rod. The stopcock was then closed, a "vent" in the cylinder was opened, cold water was introduced from another pipe to condense the steam, whereupon a vacuum formed, and the atmospheric pressure depressed the piston and lifted the pump rod. By having the various stopcocks carefully worked by hand a certain regularity of operation could be obtained, but before long improvements were made and the stopcocks were caused to work automatically. But since the cold (condensing) water chilled the cylinder, much heat was necessarily wasted.

Watt began by inventing (in 1765) a separate condenser, for cooling the steam without cooling the cylinder, - thus saving a vast amount of heat. He next abandoned altogether the use of atmospheric pressure for depressing the piston, employing steam above as well as below the piston, to lower as well as to lift it: and with these improvements, to which he added many others, he soon had in his possession a serviceable and automatic steam-engine, rudimentary in many respects, but not essentially unlike that of to-day.

THE SPINNING JENNY, THE WATER-FRAME AND THE MULE. — In 1770 James Hargreaves patented the spinning jenny, a frame with a number of spindles side by side, by which many threads could be spun at once instead of only one, as in the old, one-thread, distaff or the spinning wheel. In 1771 Arkwright operated successfully in a mill a patent spinning machine which, because actuated by water power, was known as the "water-frame." In 1779 Crompton combined the principles involved in Hargreaves' and Arkwright's machines into one, which, because of this hybrid origin, became known as the spinning "mule." This proved so successful that by 1811 more than four and a half million spindles worked as "mules" were in operation in England.

A similar machine for weaving was soon urgently needed, and in 1785 the "power loom" of Cartwright appeared, although it required much improvement and was not widely used before 1813.

THE COTTON GIN (ENGINE). With the inventions just described facilities arose for the manufacture of cotton as well as woollen, but the supply of raw cotton was limited, chiefly because of the difficulty of separating the staple (fibres) from the seeds upon which they are borne. Cotton had for centuries been grown and manufactured in