34 The Founders of Geology LECT. 



regarding the subaerial degradation of the land were now for 

 the first time proclaimed to the world. Guettard had been 

 to some extent preceded by the English naturalist Eay, 

 who, some ninety years before, had briefly alluded to the 

 manifest action of "rains continually washing down and 

 carrying away earth from the mountains," and to the 

 destruction of the shores by the continual working of the 

 sea, and who believed that in the end, by the combination 

 of these processes, the whole dry land might possibly be 

 reduced below the sea-level. 1 



Generelli, too, in his defence of Lazzaro Moro, twenty 

 years before the appearance of Guettard' s volume, had, with 

 great eloquence, dwelt on the evidence of the constant 

 degradation of the mountains by running water as an 

 argument for the existence of some other natural cause, 

 whereby, from time to time, land was upraised to com- 

 pensate for the universal waste. It must be admitted, 

 however, that no one had elaborated the subject so fully 

 until it was taken up by the French observer, and that 

 he was the first to discuss the whole phenomena of 

 denudation, apart altogether from theory, as a great domain 

 for accurate and prolonged observation. 



I have reserved for mention in the last place the dis- 

 covery for which chiefly Guettard's name has received such 

 mention as has been accorded to it in English scientific 

 literature. He was the first to ascertain the existence of 

 a group of old volcanoes in the heart of France. This 

 contribution to the geology of the time may seem in itself 



1 Miscellaneous Discourses concerning the Dissolution and Changes of 

 the World, by John Ray, Fellow of the Royal Society, London, 1692, 

 pp. 44-56. 



