Page:Biographies of Scientific Men.djvu/146

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He classified rocks, according to their origin, into four great divisions—aqueous, volcanic, plutonic, and metamorphic 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