234 EXPERIMENTS ON METAMORPHISM AND 



and subsequent depression of the celebrated conglomerates of Yalor- 

 sine, without, however, giving an opinion as to the cause of the phe- 

 nomenon.* Another discovery, due also to Hutton, had an important 

 influence on geology; I refer to the eruptive origin of granite. In 

 the study of this rock in his own country, especially at Portsoy and 

 in Glen-Tilt, he perceived that it forms veins in the surrounding 

 masses, showing that it was injected in a fluid state; and, further, 

 that its raineralogical nature indicated the action of heat. It is, 

 however, just to add that Strange, a compatriot of Hutton, had just come 

 to the same conclusion, f The rocks known to the English under the 

 names of U'ap, loadstone, and ivMnstone, have also been injected in 

 regions where there were no indications of volcanoes.:}: Hutton 

 proves this by the numerous examples which he had observed in 

 Scotland, a country eminently favorable for this kind of study. He 

 investigated, besides, the cause of the difference between these subter- 

 ranean lavas and those thrown out from volcanoes, in which neither 

 zeolites nor calc spar are found. Here, too, it is heat under pressure, 

 which appears to him to explain this difFerence.il To the author of 

 these fundamental deductions, metallic veins, as Descartes had previ- 

 ously suspected, could only be injections of melted masses. 



In short, Hutton explained the history of the globe with as much 

 simplicity as grandeur. The atmosphere is the region where the 

 rocks decompose; their detritus next accumulates at the bottom of the 

 sea. In this great laboratory the shifting material, under the double 

 action of the pressure of the ocean and of heat, is mineralized, and 

 transformed into crystalline, having the appearance of the primitive 

 rocks, which are afterwards to be raised by the action of this same 

 internal heat, and again demolished in their turn. Thfe disintegra- 

 tion of one part of the globe serves, therefore, for the continual recon- 

 struction of other parts, and the continuous destruction of the infe- 

 rior deposits produces, without cessation, rocks in a state of fusion, 

 to be injected in turn through the sedimentary deposits. It is a 

 system of destruction and of reconstruction of which it is impossible 

 to conjecture either the commencement or the end. As in the plan- 

 etary motions, where the perturbations correct themselves, we see 

 continual changes, though restrained within certain limits, of such a 

 character that the globe shows no signs either of infancy or of old 

 age. 



*"' The observations of Stenon on the same subject, which Elie de Beaumont has 

 brought to light, {Annales dc!< Sciences Namrelles,vol. xxv, p. 137 to 183,) appear to have been 

 entirely forgotten at that time. 



■j- Transactions, vol. Ixv, p. 5, 1775. 



X We must, however, remember that Desmarets bad already long ago proved the igneous 

 -origin of the basalt of Auveigne, of Italy, and of the northern coast of Ireland, (1768- 

 1771.) 



yi Speaking of the very conceivable error which Hutton committed on the origin of these 

 calcareous infilt -ations, I cannot help remarking with what penetration Spallanzani, an- 

 other great observer of nature of the same period, recognized the mixed origin oi the 

 amytzdaloid rocks of the Euganajan Hills. The rtisposition of their cavities satisfied him 

 that the rock had been melted, at the same time that the presence of carljonate of lime in 

 ttoresult from infiltrations. 



