108 BIOGRAPHIES OF SCIENTIFIC MEN 



He classified rocks, according to their origin, into four 

 great divisions aqueous, volcanic, plutonic, and meta- 

 morphic rocks. These divisions have reference to their 

 origin the agencies at work in rock formation. 



Lyell was always making geological tours in order to 

 gain information and further evidence to support the 

 great idea of his life. In 1828 he, in company with 

 Murchison, went to France, and the observations then 

 made gave rise to two papers : "On the Volcanic District 

 of Auvergne," and " On the Tertiary Formations of Aix-en- 

 Provence." In the former paper he confutes Von Buch's 

 idea of " elevation craters," and states that cones owe 

 their "origin to a series of eruptions," .... "where 

 the cavity is present, it has probably been due to one or 

 more great explosions similar to that which destroyed 

 a great part of ancient Vesuvius in the time of Pliny. 

 Similar paroxysmal catastrophes have caused in historical 

 times the truncation on a grand scale of some large cones 

 in Java and elsewhere." 



Due to studying Bonelli's collection of Tertiary shells 

 at Turin, and the marine fossils of the Tertiary rocks of 

 Sicily and Ischia, Lyell divided the Tertiaries into the 

 Eocene, Miocene, and Pliocene formations. 



In 1832 Lyell married Mary, the eldest daughter of 

 Leonard Homer. She was an accomplished linguist, 

 and her husband's companion through life, sharing his 

 labours, and " who braved with him the dangers and 



