James Hutton, the notable Scotch geologist, was born at Edinburgh on June 3, 1726. In 1743 he was apprenticed to a Writer to the Signet; but his apprenticeship was of short duration and in the following year he began to study medicine at Edinburgh University, and in 1749 graduated as an M.D. Later he determined to study agriculture, and went, in 1752, to live with a Norfolk farmer to learn practical farming. He did not devote himself entirely to agriculture, but gave a considerable amount of his time to chemical and geological researches. His geological researches culminated in his great work, "The Theory of the Earth," published at Edinburgh in 1795. In this work he propounds the theory that the present continents have been formed at the bottom of the sea by the precipitation of the detritus of former continents, and that the precipitate had been hardened by heat and elevated above the sea by the expansive power of heat. He died on March 26, 1797. Other works are his "Theory of Rain," "Elements of Agriculture," "Natural Philosophy," and "Nature of Coal."
I.—Origin and Consolidation of the Land
The solid surface of the earth is mainly composed of gravel, of calcareous, and argillaceous strata. Sand is separated by streams and currents, gravel is formed by the attrition of stones agitated in water, and argillaceous strata are deposited by water containing argillaceous material. Accordingly, the solid earth would seem to have been mainly produced by water, wind, and tides, and this theory is confirmed by the discovery that all the masses of marble and limestone are composed of the calcareous matter of marine bodies. All these materials were, in the first place, deposited at the bottom of the sea, and we have to consider, firstly, how they were consolidated; and secondly, how they came to be dry land, elevated above the sea.
It is plain that consolidation may have been effected either through the concretion of substances dissolved in water or through fusion by fire. Consolidation through the concretion of substances dissolved in the sea is unlikely, for, in the first place, there are strata, such as siliceous matter, which are insoluble, and which could not therefore have been in solution; and, in the second place, the appearance of the strata is contrary to this supposition. Consolidation was probably effected by heat and fusion. All the substances in the earth may be rendered fluid by heat, and all the appearances in the earth's crust are consistent with the consolidation and crystallisation of fused substances. Not only so, but we find rents and separations and veins in the strata, such as would naturally occur in strata consolidated by the cooling of fused masses, and other phenomena pointing to fusion by heat. We may conclude, then, that all the solid strata of the globe have been hardened from a state of fusion.
But how were these strata raised up from the bottom of the sea and transformed into dry land? Even as heat was the consolidating power, so heat was also probably the elevating power. The power of heat for the expansion of bodies is, as we know, unlimited, and the expansive power of heat was certainly competent to raise the strata above the sea. Heat was certainly competent, and if we examine the crust of the earth we find evidence that heat was used.
If the strata cemented by the heat of fusion were created by the expansive power of heat acting from below, we should expect to find every species of fracture, dislocation, and contortion in those bodies, and every degree of departure from a horizontal towards a vertical position. And this is just what we do find. From horizontal, the strata are frequently found vertical; from continuous, broken, and separated in every possible direction; and from a plane, bent and doubled. The theory is confirmed by an examination of the veins and fissures of the earth which contain matter foreign to the strata they traverse, and evidently forced into them as a fluid under great pressure. Active volcanoes, and extinct volcanoes, and the marks everywhere of volcanic action likewise support the theory of expansion and elevation by heat. A volcano is not made on purpose to frighten superstitious people into fits of piety and devotion; it is to be considered as a spiracle of a subterranean furnace.
Such being the manner of the formation of the crust of the world, can we form any judgment of its duration and durability? If we could measure the rate of the attrition of the present continents, we might estimate the duration of the older continents whose attrition supplied the material for the present dry land. But as we cannot measure the wearing-away of the land, we can merely state generally, first, that the present dry land required an indefinitely long period for its formation; second, that the previous dry land which supplied material for its formation required equal time to make; third, that there is at present land forming at the bottom of the sea which in time will appear above the surface; fourth, that we find no vestige of a beginning, or of an end.
Granite has in its own nature no claim to originality, for it is found to vary greatly in its composition. But, further, it is certain that granite, or a species of the same kind of stone, is found stratified. It is the granit feuilletée of M. de Sauffure, and, if I mistake not, is called gneiss by the Germans. Granite being thus found stratified, the masses of this stone cannot be allowed to any right of priority over the schistus, its companion in Alpine countries.
Lack of stratification, then, cannot be considered a proof of primitive rock. Nor can lack of organized bodies, such as shells, in these rocks, be considered a proof; for the traces of organized bodies may be obliterated by the many subsequent operations of the mineral region. In any case, signs of organized bodies are sometimes found in "primitive" mountains.