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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Dec. 18> 



which issues from the hase of a rock on which the ruins of the 

 ancient convent of the Celestins appears. Having heard from French 

 geologists that this rock was considered to be simply a mass of tra- 

 vertine of comparatively modern date, I was greatly surprised to find 

 exposed in a little pathway, recently cut down on the south side of 

 the cliff, a clear junction of the horizontal strata on which the town 

 is built, with absolutely vertical strata of the same materials, on the 

 tops or edges of which the monks had built their convent. Here, 

 therefore, was a very decisive fault, as represented in fig. 1 . 



In a sketch of the origin and contents of the waters of Vichy, 

 published in the year 1820*, MM. Berthier and Puvis showed very 



Fig. 1, — Section of the "Rocker des Celestins" 



c a 



a. Limestone and travertine of the Celestins in the original horizontal condition. 

 a', a'. The same, dislocated and vertical. 

 c. Alluvium of the river-bank. 



correctly, that, judging from its composition, this "Rocher des 

 Celestins" must have been the produce of mineral sources. This 

 rock, said they, is so characterized by the fibrous and concretionary 

 structure prevalent in all such tufaceous deposits, and which is in- 

 deed apparent in the residuum left by the existing waters of Vichy, 

 where, parting with their carbonic acid gas, they throw down the 

 salts previously held in solution, that doubtless the rock of the Ce- 

 lestins had a similar origin. But much more explanation than this 

 is required to account for the position of the layers of the Rocher des 

 Celestins. The geological description of these authors requires, in 

 short, correction ; for no allusion is made by them to the rock being 



* " Notice sur les eaux de Vichy," Annales des Mines, 1820, vol. v. p. 413. 

 In the sketch MM. Berthier and Puvis have erred in speaking of granite as the 

 fundamental rock of the district of Vichy. They referred in this case, I presume, 

 to the known relations of the adjacent district of Auvergne, where the tertiary 

 lacustrine deposits rest on granite. Here, however, the crystalline rocks are 

 porphyries and greenstones, which have perforated the adjacent older carboni- 

 ferous deposits. See ante, p. 14 of this volume. 



