﻿1850.] MURCHISON ON THE MINERAL SPRINGS OF VICHY. 



77 



of various crystalline and schistose rocks, quartz, &c. These are 

 surmounted by finely laminated foxy-coloured sands, and those again 

 by other and finer pebble beds ; the last-mentioned being in many 

 places again covered by coarse drift. In the geological map of France 

 the lowest of these pebbly accumulations are represented as younger 

 tertiary. Whatever their relative age may be, they were manifestly all 

 formed under water, which was subjected to great motion, as proved 

 by their water-worn boulders of granite, porphyry, schist, quartz 

 rock, &c. This coarse detrital deposit forms the greatest possible 

 contrast to the minutely aggregated sediment of limestone and marl 

 which had been previously accumulated in a vast interior lake or in 

 several lakes. 



And here I would say, that the clearest distinction must be drawn 

 between the above-mentioned ancient detritus of the plateaux and 

 slopes of the hills of the Limagne d'Auvergne, and that which is the 

 produce of the present rivers. In the wide spreading bed of the 

 Allier, which is encumbered with the rocks in question, few or none 

 of the fragments have been derived by that stream from the parent 

 rocks, but have simply been carried into it in floods by the wearing 

 away of banks of the ancient drift, which has been lodged at various 

 elevations, from the lowest depressions, to plateaux 500 or 600 feet 

 above the river beds. I am not aware that any organic remains have 

 been found in this great detrital formation by which its age could be 

 precisely attested. 



The mineral waters of Vichy rise along a fissure, parallel to the 

 course of the Allier. This fissure must have traversed a portion of 

 the lacustrine limestones and marls, since that formation rises up 

 into hills on either side of the depression in which the springs occur. 

 The valley is, however, so encumbered with detritus of the overlying 

 and reaggregated pebble beds, that except at the town of Vichy it is 

 almost impossible to make good observations. There, a few rocky 

 mounds rise a little above the Allier, and have served for the site of 

 the ancient " Bourg." In some parts these are undistinguishable 

 from the cream-coloured marls and limestone of the surrounding hills, 

 in others there is indication of their having been accumulated as 

 travertine or tuff, which was formed contemporaneously with the 

 earliest of these tertiary rocks. These beds are horizontal or very 

 slightly undulating, as seen under various buildings, including the 

 great round tower, which overhangs the Allier to the south of the 

 mansion formerly occupied by Madame de Sevigne*. There can be 

 no doubt that these deposits, whether formed by ordinary lacustrine 

 sediment or by the action of mineral sources, are of remote age in 

 relation to our own period ; for no springs have issued in the historic 

 time within the ancient town from which they could have been 

 formed. 



The mineral sources issue, in fact, at lower levels, i. e. both to the 

 north and to the south of the rocks on which the old Bourg of Vichy 

 is built. The most southern of these is the celebrated cold spring 



* The letters of Madame de Sevigne, vol. v. p. 72 et seq., were written in this 

 house. 



