W Dr Lyell on the Age of the 



termediate place of refreshment or of rest. In a word, America and 

 Polynesia appear to have been chiefly, if no solely, colonized from 

 one and the same general region of Eastern K&vSi.-^Narrative of a 

 Journey round the World, hy Sir George Simpson, vol. ii. p. 2. 



On the Age of the Volcanoes of Auvergne as determined by the 

 Remains of successive Groups of Land Quadrupeds. By C. 

 Lyell, Esq., F.R.S., &c.* 



The region of extinct volcanoes of Auvergne derives its peculiar 

 interest from the circumstance of its never having been submerged 

 beneath the sea during a period in which its geological and geogra- 

 phical structure, and the animals and plants by which it has been in- 

 habited, have undergone a great succession of changes. In the rest 

 of Europe, generally, the volcanic rocks have either been originally 

 of submarine origin, or the surface, since they were produced, has 

 suffered so much denudation by the action of the waves of the ocean 

 as to make it impossible for us to ascertain the form and manner in 

 which the eruptions took place, or the relative position which the 

 igneous formations held at first to the hills, plains, and valleys then 

 existing. After describing the several classes of rocks in Auvergne, 

 — the granite, the eocene fresh water, and the older and modern vol- 

 canic, each depicted by different colours in an extensive landscape, 

 enlarged from a view of the valley of Chambon (Puy de Dome), by 

 Mr P. Scrope, — Mr Lyell said he should dwell chiefly on the anti- 

 quity to be ascribed to the Puy de Tartaret, a type of one of the 

 most modern cones of eruption in Central France. The compara- 

 tively recent origin of this conical hill of scoriae, with its crater at 

 the summit, is proved by its standing at the bottom of a deep valley 

 excavated through the alternating beds of pumice, trachyte, and ba- 

 salt, belonging to the more ancient volcano of Mont Dor, and partly 

 through the subjacent and fundamental granite. It is farther con- 

 firmed by the course of a powerful current of lava ; which, proceed- 

 ing from the base of the cone, flows thirteen miles down the channel 

 of the river Couze, stopping at the town of Nethers, near Issoire. 

 The lava occupies the ancient river bed, and is observed to contract 

 in its dimensions in the narrow gorges, where it also gains in height, 

 like the water of a river flowing through the arch of a bridge ; and 

 to expand again where the valley opens, where it speads into a broad 

 sheet having a level surface. It also flows up the channels of tribu- 

 tary streams till it attains a level corresponding with the top of the 

 lava at the point of junction of the tributary with the main valley. 

 But although these appearances prove that the lava has flowed as 

 it would now do if it were remelted and made again to descend the 



* Account of a Lecture read before th« Royal Institution on April 20, 1847, 

 by Mr Lyell. — Athenceum. 



