Abstracts of Memoirs. 351 
3. Les Eaux MINERALES DU Massir CENTRAL DE LA FRANCE, CONSIDEREES DANS LEUR 
RAPPORTS AVEC LA CuImMig ET LA GkoLocre. Par Henri Lecoe, Professeur A la 
Faculté des Sciences de Clermont, &c. Paris, 1864. Pp. 302.—(The Mineral 
Springs of the Central Plateau of France.) 
“gas volume is a sequel to Professor Lecoq’s general work on 
mineral springs, very recently published and already noticed in 
these pages.* Itis an application of the principles there enunciated 
to the case of Central France, and is the first instalment of a work 
in preparation by its author on the geological epochs of Auvergne. 
In the classification of the mineral waters of France, M. Lecogq, 
following M. Deville, adopts a mixed geographical and chemical 
division into five groups, each characterized by the presence of a 
class of salts. These groups are as follows :—Ist. The waters of 
the Central Plateau of France, where the bicarbonates are present in 
the proportion of 75 per cent. These waters contain upwards of 
300 grains of solid matter to the gallon.—2nd. The mineral springs 
of the Alps and Corsica, characterized by sulphaées in the proportion 
of about 43 per cent., but not containing more than 170 grains to 
the gallon.—8rd. The springs of the Vosges, the Jura, and the hills 
of the Upper Sadne. These contain 67 per cent. of chlorides, and 
240 grains to the gallon.—4th. Those of the Ardennes and Hainault, 
characterized both by bicarbonates and chlorides. The first are in 
the ratio of 49 per cent., and the others 48. The solids are about 
105 grains per gallon.—5th. The springs of the North-west Plateau, 
or Brittany, containing about 30 per cent. of sulphates, 88 per cent. 
of bicarbonates, and 23 per cent. of chlorides ; but the whole solid 
contents are not more than 40 grains per gallon. 
Locally M. Lecog establishes fifteen groups of springs—seven in 
the department of Puy-de-Déme, the rest in adjacent departments. 
‘The former are the more generally known, and the more interesting 
in a geological sense. Of its seven groups, that of Mont Dore is 
the first considered. Mont Dore consists of a mass of volcanic 
rock, nearly 3,000 feet thick in places, and situated on a granitic 
plateau.* Fissures have been formed in this erupted mass after 
cooling dislocations have taken place, and mineral springs rise in 
the long valleys of Mont Dore and Chaudefour, radiating from the 
centre of the mountain-group. In the Mont-Dore Valley (Dordogne) 
are several groups issuing from trachyte. In the Chaudefour they 
are from crevices in the granite. 
In the upper part of the valley of the Dordogne is the spring 
called la Cheminée du Diable (the Devil’s Chimney). It is situated 
at the foot of the Pic de Sancy, and is not very accessible. It is 
singular to see a deposit of iron and limestone amidst trachyte. 
The minerals have been left behind by the spring, which is now 
small and cold. M. Lecoq believes that the carbonate of lime comes 
in this case from beneath the granite underlying the trachyte. 
Several adjacent springs are ferruginous. 
The Mont-Dore springs may be regarded as seven in number, but 
each includes a small group. ‘Their temperature varies from 108° 
* See Grou. Mace., Vol. II. pp. 115 and 164. 
t The highest point of the Pic de Sancy is 6,130 feet above the sea. 
