ancient Gj/psum of the Alps. 73 



little attention to this circumstance, which now becomej 

 very important from the existence of gypsum on the Allee 

 Blanche, of a deposit of gypsum in the Valais (that of St. 

 Leouhard) on an anthracite formation, and of another (that 

 of Brigg) in a formation that is analogous to it. 



Lastly, as I have already announced, gypsum is found 

 even in the works of the mine of Pesey, and this is the 

 place to discuss the true characters of this position, because 

 it is very important. 



There is no question here of the small portions of anhy- 

 drous sulphate of lime, that are sometimes met with in the 

 mass even of the ore or metalliferous rock, and which have 

 been collected in cabinets. They are easily admitted to be 

 owing to infiltrations from the upper parts ; I mean to speak 

 of the considerable masses of gypsum and anhydrous sulphate 

 of lime, the debris of which cover the refuse of the mines 

 (haldes). 



These gypsum masses do not exist in the works carried on 

 for the ore, they do not contain a trace of it ; they are only 

 met with in the adit level, and solely in the portion of this 

 gallery above the useful works. The gypsum is then evi- 

 dently above the metalliferous rock. This position has been 

 fully admitted ; but it may equally happen in two very 

 different cases : either the gypsum there forms a distinct 

 bed belonging to the same system as the rock, or else it has 

 been deposited upon it at a period sul)sequent to its consoli- 

 dation, and constitutes part of a different formation. 



The surface cannot afford any information in this respect, 

 being entirely covered by tuffa, pasturage, and wood, the 

 gypsum not shewing itself. It is met with only at the hamlet 

 of Beaupraz, at 1200 metres [3937 ft.] distance, ascending 

 the valley ; it occurs there at the surface, forming an insu- 

 lated mass of small extent, at the foot of one of the slopes, 

 where it loses itself under the vegetable soil. 



The other characters that 1 have noticed above the Taren- 

 taise gypsum led me already to presume that this gypsum 

 covered the rock, that its formation was more modern, and 



