under new aspects; they disturb the public sloth; and they interrupt, rudely, but with most salutary effect, that love of routine, which, by inducing men to go grovelling on in the ways of their ancestors, stands in the path of every improvement, as a constant, an outlying, and, too often, a fatal obstacle.

The method adopted by Werner was evidently deductive, since he argued from a supposed cause, and reasoned from it to the effects. In that cause, he found his major premiss, and thence he worked downwards to his conclusion, until he reached the world of sense and of reality. He trusted in his one great idea, and he handled that idea with consummate skill. On that very account, did he pay less attention to existing facts. Had he chosen, he, like other men, could have collected them, and subjected them to an inductive generalization. But he preferred the opposite path. To reproach him with this is irrational; for, in his journey after truth, he chose one of the only two roads which are open to the human mind. In England, indeed, we are apt to take for granted that one road is infinitely preferable to the other. It may be so; but on this, as on many other subjects, assertions are current which have never been proved. At all events, Werner was so satisfied with his method, that he would not be at the pains of examining the position of rocks and their strata, as they are variously exhibited in different countries; he did not even explore his own country, but, confining himself to a corner of Germany, he began and completed his celebrated system, without investigating the facts on which, according to the inductive method, that system should have been built.1

176

176"If it be true that delivery be the first, second, and third requisite in a popular orator, it is no less certain that to travel is of first, second, and third importance to those who desire to originate just and comprehensive views concerning the structure of our globe. Now, Werner had not travelled to distant countries: he had merely explored a small portion of Germany, and conceived, and persuaded others to believe, that the whole surface of our planet, and all the mountain chains in the world, were made after the model of his own province." . . . . "It now appears that he had misinterpreted many of the most important appearances even in the immediate neighbourhood of Freyberg. Thus, for example, within a day's journey of

Exactly the same process, on the same subject, and at the same time, was going on in Scotland. Hutton, who was the founder of Scotch geology, and who, in 1788, published his Theory of the Earth, conducted the inquiry just as Werner did; though, when he began his speculations, he had no knowledge of what Werner was doing."" The only difference between them was, that while Werner reasoned from the agency of water, Hutton reasoned from the agency of fire. The cause of this may, I think, be explained. Hutton lived in a country where some of the most important laws of heat had, for the first time, been generalized, and where consequently, that department of inorganic physics had acquired great reputation. It was natural for a Scotchman to take more than ordinary interest in a subject in which Scotland had been so successful, and had obtained so much fame. We need not, therefore, wonder that Hutton, who, like all men, felt the intellectual bent of the time in which he lived, should have yielded to an influence of which he was, perhaps, unconscious. In obedience to the general mental habits of his country he adopted the deductive method. In further obedience to the more special circumstances connected with his own immediate pursuits, he gathered the principles from which he reasoned from a study of fire, instead of gathering them, as Werner did, from a study of water.

Hence it is, that, in the history of geology, the followers of Werner are known as Neptunists, and those of Hutton as Plutonists.178 And these terms represent the

his school, the porphyry, called by him primitive, has been found not only to send forth veins, or dykes, through strata of the coal formation, but to overlie them in mass." Lyell's Principles of Geology, p. 47.

177 Though Hutton's Theory of the Earth was first published in 1788, the edition of 1795, which is the one I have used, contains a great number of additional illustrations of his views, and was evidently re-written. But the main features are the same; and we learn from his friend, Playfair, that "the great outline of his system" was completed "several years" before 1788. Life of Hutton, in Playfair's Works, vol. iv. p. 50, Edinburgh, 1822. 178 Kirwan appears to have been the first who called Hutton's theory "the Plutonic System." See Illustrations of the Huttonian Theory in PlayWorks, vol. i. p. 145. On the distinction between Neptunists and nists, see the saine work, pp. 504, 505.

only difference between the two great masters. In the most important points, namely their method, they were entirely agreed. Both were essentially one-sided; both paid a too exclusive attention to one of the two principal agents which have altered, and are still altering, the crust of the earth; both reasoned from those agents, instead of reasoning to them; and both constructed their system without sufficiently studying the actual and existing facts; committing, in this respect, an error which the English geologists were the first to rectify.

As I am writing a history, not of science, but of scientific method, I can only briefly glance at the nature of those services which Hutton rendered to geology, and which are so considerable, that his system has been called its present basis. 179 This, however, is too strongly expressed; for, though Hutton was far from denying the influence of water, 180 he did not concede enough to it, and there is a tendency among several geologists to admit that the system of Werner considered as an aqueous theory, contains a larger amount of truth than the advocates of the igneous theory are willing to allow. Still, what Hutton did was most remarkable, especially in reference to what are now termed metamorphic rocks, the theory of whose formation he was the first to conceive.181 Into this, and into their connexion, on the one hand, with the sedimentary rocks, and, on the other hand, with those rocks whose origin is perhaps purely igneous, I could not enter without treading on debatable ground. But, putting aside what is yet uncertain, I will mention two circumstances respecting Hutton which are undisputed, and which will give some idea of his method, and

179 "Has not only supplanted that of Werner, but has formed the foundation of the researches and writings of our most enlightened observers, and is justly regarded as the basis of all sound geology at the present day." Richardson's Geology, London, 1851, p. 38.

180 Hutton's Theory of the Earth, Edinb. 1795, vol. i. pp. 34, 41, 192, 290, 291, 593, vol. ii. pp. 236, 369, 378, 555.

181 "In his writings, and in those of his illustrator, Playfair, we find the germ of the metamorphic theory." Lyell's Manual of Geology, London, 1851,

p. 92.

of the turn of his mind. The first circumstance is, that, although he ascribed to subterranean heat, as exhibited in volcanic action, a greater and more constant energy than any previous inquirers had ventured to do,182 he preferred speculating on the probable consequences of that action, rather than drawing inferences from the facts which the action presented; he being on this point so indifferent, that he arrived at his conclusions without inspecting even a single region of active volcanoes, where he might have watched the workings of nature, and seen what she was really about.183 The other circumstance is equally characteristic. Hutton, in his speculations concerning the geological effects of heat, naturally availed himself of the laws which Black had unfolded. One of those laws was, that certain earths owe their fusibility to the presence of fixed air in them before heat has expelled it; so that if it were possible to force them to retain their fixed air, or carbonic acid gas, as we now call it, no amount of heat could deprive them of the capability of being fused. The fertile mind of Hutton saw, in this discovery, a principle from which he could construct a geological argument. It occurred to him, that great pressure would prevent the escape of fixed air from heated rocks, and would thus enable them to be fused, notwith

182 The shortest summary of this view is in his Theory of the Earth, Edin. 1795, vol. ii. pp. 556. "The doctrine, therefore, of our Theory is briefly this; That whatever may have been the operation of dissolving water, and the chemical action of it upon the materials accumulated at the bottom of the sea, the general solidity of that mass of earth, and the placing of it in the atmosphere above the surface of the sea, has been the immediate operation of fire or heat melting and expanding bodies."

183 44 Although Hutton had never explored any region of active volcanos, he had convinced himself that basalt and many other trap rocks were of igneous origin." Lyell's Principles of Geology, London, 1853, p. 51. To this I may add, that he wrote his work without having examined granite. He says (Theory of the Earth, vol. i. p. 214), "It is true, I met with it on my return by the east coast, when I just saw it, and no more, at Peterhead and Aberdeen; but that was all the granite I had ever seen when I wrote my Theory of the Earth. I have, since that time, seen it in different places; because I went on purpose to examine it, as I shall have occasion to describe in the course of this work." Hutton's theory of granite is noticed in Boke well's Geology, London, 1838, p. 101; but Mr. Bakewell does not seem to be aware that the theory was formed before the observations were made.

standing their elevated temperature. He then supposed that, at a period anterior to the existence of man, such a process had taken place under the surface of the sea, and that the weight of so great a column of water had prevented the rocks from being decomposed while they were subjected to the action of fire. In this way, their volatile parts were held together, and they themselves might be melted, which could not have happened except for this enormous pressure. By following this line of argument, he accounted for the consolidation of strata by heat; since, according to the premisses from which he started, the oily, or bituminous parts, would remain, in spite of the efforts of heat to disperse them.184 This striking speculation led to the inference, that the volatile components of a substance, and its fixed components, may be made to cohere, in the very teeth of that apparently irresistible agent whose business it is to effect their separation. Such an inference was contrary to all experience; or, to say the least, no man had ever seen an instance of it.185 Indeed, the event was only supposed to happen in consequence of circumstances which were never met with on the surface of the globe, and which, therefore, were out of the range of all human observation.186 The utmost that could be expected was, that, by means of our instruments, we might, perhaps, on a small scale,

184 Huttonian Theory, in Playfair, vol. i. pp. 38-40, 509, 510. Compare Playfair's Life of Hutton, p. 61.

185 Hence, the objections of Kirwan were invalid; because his argument against Hutton was "grounded on experiments, where that very separation of the volatile and fixed parts takes place, which it excluded in that hypothesis of subterraneous heat." Huttonian Theory, in Playfair, vol. i. p. 193, Edinb. 1822.

186 Hutton says (Theory of the Earth, Edinb. 1795, vol. i. p. 94), “The place of mineral operations is not on the surface of the earth; and we are not to limit nature with our imbecility, or estimate the powers of nature by the measure of our own." See also p. 159, "mineral operations proper to the lower regions of the earth." And p. 527, "The mineral operations of nature lie in a part of the globe which is necessarily inaccessible to man, and where the powers of nature act under very different conditions from those which we find take place in the only situation where we can live." Again, in vol. ii. p. 97, “The present Theory of the Earth holds for principle that the strata are consolidated in the mineral regions far beyond the reach of human observation." Similarly, vol. ii. p. 484, "we judge not of the progress of things from the actual operations of the surface."