An Introduction to the History of Science

by Walter Libby

He expressed the wish to induce men who had sufficient knowledge of the particular branches of science, to employ their acquired talents in promoting general science, or knowledge of the great system, where ends and means are wisely adjusted in the constitution of the material universe. Philosophy, he says, is surely the ultimate end of human knowledge, or the object at which all sciences properly must aim. Sciences no doubt should promote the arts of life; but, he proceeds, what are all the arts of life, or all the enjoyments of mere animal nature, compared with the art of human happiness, gained by education and brought to perfection by philosophy? Man must learn to know himself; he must see his station among created things; he must become a moral agent. But it is only by studying things in general that he may arrive at this perfection of his nature. "To philosophize, therefore, without proper science, is in vain; although it is not vain to pursue science, without proceeding to philosophy."

In the early part of 1785 Dr. Hutton presented his Theory of the Earth in ninety-six pages of perfectly lucid English. The globe is studied as a machine adapted to a certain end, namely, to provide a habitable world for plants, for animals, and, above all, for intellectual beings capable of the contemplation and the appreciation of order and harmony. Hutton's theory might be made plain by drawing an analogy between geological and meteorological activities. The rain descends on the earth; streams and rivers bear it to the sea; the aqueous vapors, drawn from the sea, supply the clouds, and the circuit is complete. Similarly, the soil is formed from the overhanging mountains; it is washed as sediment into the sea; it is elevated, after consolidation, into the overhanging mountains. The earth is more than a mechanism, it is an organism that repairs and restores itself in perpetuity. Thus Hutton explained the composition, dissolution, and restoration of land upon the globe on a general principle, even as Newton had brought a mass of details under the single law of gravitation.

Again, as Newton had widened man's conception of space, so Hutton (and Buffon) enlarged his conception of time. For the geologist did not undertake to explain the origin of things; he found no vestige of a beginning,—no prospect of an end; and at the same time he conjured up no hypothetical causes, no catastrophes, or sudden convulsions of nature; neither did he (like Werner) believe that phenomena now present, were once absent; but he undertook to explain all geological change by processes in action now as heretofore. Countless ages were requisite to form the soil of our smiling valleys, but "Time, which measures everything in our idea, and is often deficient to our schemes, is to nature endless and as nothing." The calcareous remains of marine animals in the solid body of the earth bear witness of a period to which no other species of chronology is able to remount.

Hutton's imagination, on the basis of what can be observed to-day, pictured the chemical and mechanical disintegration of the rocks; and saw ice-streams bearing huge granite boulders from the declivities of primitive and more gigantic Alps. He believed (as Desmarest) that rivulets and rivers have constructed, and are constructing, their own valley systems, and that the denudation ever in progress would be eventually fatal to the sustenance of plant and animal and man, if the earth were not a renewable organism, in which repair is correlative with waste.

All strata are sedimentary, consolidated at the bottom of the sea by the pressure of the water and by subterranean heat. How are strata raised from the ocean bed? By the same subterranean force that helped consolidate them. The power of heat for the expansion of bodies, is, says Hutton (possibly having in mind the steam engine), so far as we know, unlimited. We see liquid stone pouring from the crater of a lofty volcano and casting huge rocks into mid-air, and yet find it difficult to believe that Vesuvius and Etna themselves have been formed by volcanic action. The interior of the planet may be a fluid mass, melted, but unchanged by the action of heat. The volcanoes are spiracles or safety-valves, and are widely distributed on the surface of the earth.

Hutton believed that basalt, and the whinstones generally, are of igneous origin. Moreover, he put granite in the same category, and believed it had been injected, as also metalliferous veins, in liquid state into the stratified rocks. If his supposition were correct, then granite would be found sending out veins from its large masses to pierce the stratified rocks and to crop out where stratum meets stratum. His conjecture was corroborated at Glen Tilt (and in the island of Arran). Hutton was so elated at the verification of his view that the Scotch guides thought he had struck gold, or silver at the very least. In the bed of the river Tilt he could see at six points within half a mile powerful veins of red granite piercing the black micaceous schist and giving every indication of having been intruded from beneath, with great violence, into the earlier formation.

Hutton felt confirmed in his view that in nature there is wisdom, system, and consistency. Even the volcano and earthquake, instead of being accidents, or arbitrary manifestations of divine wrath, are part of the economy of nature, and the best clue we have to the stupendous force necessary to heave up the strata, inject veins of metals and igneous rocks, and insure a succession of habitable worlds.

In 1795 Dr. Hutton published a more elaborate statement of his theory in two volumes. In 1802 Playfair printed Illustrations of the Huttonian Theory, a simplification, having, naturally, little originality. Before his death in 1797 Hutton devoted his time to reading new volumes by Saussure on the Alps, and to preparing a book on The Elements of Agriculture.

Sir James Hall of Dunglass was a reluctant convert to Hutton's system of geology. Three arguments against the Huttonian hypothesis gave him cause for doubt. Would not matter solidifying after fusion form a glass, a vitreous, rather than a crystalline product? Why do basalts, whinstones, and other supposedly volcanic rocks differ so much in structure from lava? How can marble and other limestones have been fused, seeing that they are readily calcined by heat? Hutton thought that the compression under which the subterranean heat had been applied was a factor in the solution of these problems. He was encouraged in this view by Black, who, as already implied, had made a special study of limestone and had demonstrated that lime acquires its causticity through the expulsion of carbonic acid.

Hall conjectured in addition that the rate at which the fused mass cooled might have some bearing on the structure of igneous rocks. An accident in the Leith glass works strengthened the probability of his conjecture and encouraged him to experiment. A pot of green bottle-glass had been allowed to cool slowly with the result that it had a stony, rather than a vitreous structure. Hall experimenting with glass could secure either structure at will by cooling rapidly or slowly, and that with the same specimen.