At about a third of the way the Dordogne is crossed, and shortly afterwards is passed the ravine of the Egravats, formed by a landslip of the Trachytic mountain, the Roc de Cuzeau, 5706 ft.
"The South of France--East Half"
Charles Bertram Black
The mountain Labo appears from its bell-shape and the strata exposed in the river bed to consist of Trachytic hornblende.
"The Former Philippines thru Foreign Eyes"
Tomás de Comyn Fedor Jagor Rudolf Ludwig Carl Virchow Charles Wilkes
The mountain is composed of Trachytic rocks and tufa, which are occasionally seen to break through the rich and deep soil, showing themselves here and there, in the deep valleys which former volcanic action has created, and which have destroyed the regular outline of the cone-shaped mountain.
"The Former Philippines thru Foreign Eyes"
Tomás de Comyn Fedor Jagor Rudolf Ludwig Carl Virchow Charles Wilkes