ON THE FORMATION OF CRYSTALLINE ROCKS. 235 



In considering- this action as a continuous phenomenon, Hntton ob- 

 scured his l)eautifiil conception, but he rendered an immense servMce 

 in showing that natural agencies which operate under our eyes ought 

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

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

 which nature now uses, Avhile 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 sediun'iitary 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 which 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 water 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 Avhich 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 b« 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 flints 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 Buffon the central fire is supposed to have acted 

 only at the origin of the globe, before the formatiim of deposits. Combatiug 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 iu 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 upon which he based his theories. 



\\Og:crva2ioni Chimirhe sopra Akuni Fossili ; Venice, 1779. After having been employed 

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

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

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



" It appears to me," says Arduino, " that magnesia is only lime, possesse 1 of peculiar 

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

 great ruptures of the calcareous beds of our mountains " 



It is extremely remarkable th;tt this riew and bold a.-^sertion was made during the very 

 year that magnesia was discovered by the experiment of PiCtzius and Bergmanti to be an 

 earth distinct from lime It was not until eleven years later, in 1791, that Doloiuieu 

 called attetition to a peculiar kind of magnesiin limestone which he had uoticel in Southern 

 Tyrol. — {Journal de Physique, vol. xxxix, p. 3.) The next year Theodore de Saussure pub- 

 lished the analysis of tliis rock, and gave it the name of dolomite, which it has still t^xh- 

 seT\tid— (Journal de P/iysique, vol. xl, p. 161 ) 



