The author having, on former occasions, stated some results of his travels in Auvergne and the Cantal, gives a more detailed description of the volcanoes of the Vivarais, which have been less frequently and less accurately described.

He first gives an account of the journey from Le Puy across the chain of the Cevennes which culminate at the volcanic summit of the Mezeuc, by the course of the Loire, to Montpezat in the department of the Ardêche.