^ON THE FORMATION OF CRYSTALLINE ROCKS. 235 



111 considering this action as a continuous phenomenon, Hutton ob- 

 scured his beautiful conception, but he rendered an immense service 

 in showing" that natural agencies which operate under our eyes ought 

 to serve as a sufficient explanation of the history of the globe, and 

 that we need not have recourse to other means of action than those 

 which nature now uses, while all the other systems, on the contrary, 

 suppose occurences which have no analogy with what now takes place. 

 Thus Hutton is really the founder of the prolific principle of the 

 transformation of sedim<>.ntary rocks under the action of heat. 



However, we shall see, further on, that there are a great many 

 exceptions to be made to such absolute conclusions.* Like most men 

 of genius who have opened new paths, Hutton, it must be admitted, 

 exaggerated the range of the ideas ^vhich he originated. We can- 

 not, however, reflect without admiration on the profound penetra- 

 tion and the rigor of induction of this clear-sighted man, who, at a 

 period when there were very few precise observations, was the first 

 to recognize the simultaneous action of w^ater and heatf in the forma- 

 tion of the strata, and imagined a system which embraces the entire 

 physical history of the globe. He laid down principles which are 

 now universally admitted, at least so far as they are fundamental.! 



CHAPTER III, 

 SUCCESSORS OF HUTTON. 



Even before the publication of Hutton' s doctrine an Italian ob- 

 server brought to light a fact from which he inferred that recent 

 igneous action may transform sedimentary rocks, even such as are 

 most modern. As early as 1779 Arduinoll announced in the clearest 



- Iron pyrites, so abundantly distributed, as well as all the minerals of veins, appeared to 

 him to be the productions of the dry way ; it served him as a proof of the action of heat 

 which the strata had undergone. He extended this observation to the fliuts of the chalk, 

 the solidity of which contrasts with the physical state of the silica known in laboratories. 



t In the cosmologies of Leibnitz and Bufiun the central fire is supposed to have acted 

 only at the origin of the globe, before the formation of deposits. Combating certain ideas 

 which were in vogue, Hutton clearly shows that the internal heat of the earth can exist 

 without any interior inflammation or combustion. 



J Hutton, born in 1726, made observations in the wildest parts of Scotland, and medi- 

 tated more than forty years before publishing his first sketch. The sight of the veins of 

 granite of the valley of Glen-Tilt struck him as with a ray of light. He himself dis- 

 covered a larger part of the facts upou which he based his theories. 



\\Os}ervazioni Chiiniche sopra Ahum Fosiili; Venice, 1779. After having been employed 

 at the mine of Montieri, in the Maremme of Sienna, Arduino went to live at Vicenza, 

 whore he was a surveyor. (Letters of Fortis on Vicentin.) Pazini has noticed his work 

 in the BulUtin of the Geological Soafly of France, vol. iv, p. 112. 



'• It appears to me," says Arduino, " that magnesia is only lime, possessed of peculiar 

 properties consequent upon subterraneous igneous action.'' •' I have only found it in the 

 great ruptures of the calcareou.s beds of our mountains " 



It i.s extremely remarkable that this new and bold assertion was made during the very 

 year that magnesia was discovered by the experiment of Retzius anrl Bergoiann to be an 

 earth (li.<tinct from lime It was not until eleven years later, in 1701, that Dolomieu 

 called attention to a peculiar kind of maguesian limestone which he had noticed in Southern 

 Tyrol. — {Journal de Physique, vol. xxxix, p. o.) The next year Theodore de Sau.^sure pub- 

 lished the analysis of this rock, and gave it the name of dolomite, which it has still pre- 

 served. — [Journal de Physique, vol. xl. p. 161.) 



