508 Notices of Memoirs — 



was found, containing in its upper part many vegetable remains, and 

 in the lower, numerous medals of bronze, silver and gold, as well as 

 other works of art of Eoman age. Below this was a bed consisting 

 principally of fragments of sandstone, which were more or less 

 cemented together by metalliferous minerals definitely crystallized. 



M. Daubree's attention was directed to this interesting circumstance 

 by the Minister of Public Works, who had received specimens from 

 the chief engineer of mines, M. Trautman. 



Notwithstanding the resemblance of these minerals to those of 

 older geological date, they have evidently been produced after the 

 embedding of the Eoman medals with which they were associated, 

 for, in many instances, the medals were encrusted and enveloped by 

 them. The following species were recognized : — 



Copper Glance, in crystals similar to those found near Eedruth, 

 in Cornwall, and associated with Covelline. 



Copper Pyrites crystallized and mammillated. 



Erubescite in regular octahedrons, and cubes with faces slightly 

 curved. 



Tetrahedrite in crj^stals with its usual lustre and other characters, 

 and from the analysis representing a type nearly free from arsenic. 



Of these minerals, the most novel is the formation of the double 

 sulphide of copper and antimony constituting Tetrahedrite, for the 

 other species have been previously observed under somewhat similar 

 conditions in other localities. 



Besides these, occur numerous rounded grains of quartz, cemented 

 with sulphides, as well as some doubly-terminated crystals of the 

 same mineral, resembling the Compostella Hyacinth. Whilst some 

 of these are derived from the gres des Vosges, others appear to have 

 been the result of a contemporaneous crystallization with that of the 

 Tetrahedrite, etc. 



The formation of these sulphides is evidently connected with the 

 thermal spring, the water of which contains in solution chlorides 

 and sulphates of the alkalies, lime and magnesia, as well as bromides, 

 and carbonates of iron and lime, an alkaline silicate, and traces of 

 arsenic and manganese. The solid contents are about 7 to 8 grammes 

 per litre, and the temperature is about 60°. 



In explaining the formation of these metallic sulphides in the 

 midst of the mud and under the influence of the mineral water which 

 has constantly penetrated it, M. Daubree considers that the sulphates 

 have been partially reduced to sulphides by the action of the vege- 

 table matter present, a well-known reaction in nature. 



The presence of antimony, an essential element in tetrahedrite, is 

 particularly interesting, for, though its presence has been determined 

 in mineral springs in other localities, it has not been recognized at 

 present in that of Bourbonne-les-Bains. It has been, therefore, 

 probably derived from the minerals used in the manufacture of the 

 bronzes, traces of this metal having been found in ancient bronze by 

 M. Fellenberg. 



The medals present a curious modification. Most of them, whilst 

 retaining their general form, have lost their sharpness of outline, so 



