ancient Gypsum of the Alps. 73 



rock, since it not only covered it, but filled if not a cleft 

 that traversed it, at least a cavity, or hollow on its surface. 

 The annexed plans and sections (plate 2, fig. 2, 3, 4, & 5), 

 represent in an exact manner the different works noticed, 

 and the relative position of the beds of the metalliferous 

 rock and the gypsum.* 



It would have been desirable, in order to complete this 

 determination of the position of the gypsum, to continue the 

 principal gallery in the midst of its mass, in a direction per- 

 pendicular to the vertical wall noticed above, so as to meet 

 with the other side of this cavity ; but the expense might 

 have been very considerable, and the poor state of the ore 

 did not authorise it. 



Uniting this last fact with the others before noticed, it is 

 seen that all the characters I have been able to collect upon 

 the gypsum of the Tarentaise, lead to the conclusion that it 

 is above the transition rocks, and of a more modern forma- 

 tion, at least in general; for, from the other positions I am 

 about to describe, it is not impossible that gypsum may be 

 discovered even in the midst of this transition series. 



2. Gi/psum of the Mlee blanche. 



It is on the right slope of this valley that the gypsum oc- 

 curs ; it there forms many white pyramidal masses, two of 

 which are very near the torrent : I saw three others at a dis- 

 tance scattered on the slope to the height of 1000 metres 

 [3281 feet] above the valley, that is io say, an absolute 

 height of 2000 to 2400 metres [6562 to 7874 feet]. I only 



* Figs. 2 and 3, plate 2, are the plan and section of that part of the 

 lower workings of the mine of Pesey which is here noticed ; the line of 

 demarcation between the gypsum and the schistose metalliferous rock is 

 there traced, as far at least as it could be determined by means of the 

 draining galleries 1 and 3, the pits 2 and 4, and others that cut this line, 

 and lastly by means of the gallery No. 5, which is that of the geologists, 

 of which I have spoken. 



Figs. 4 and 5, are the plan and section of this gallery, upon a scale 

 twenty times larger. They shew the vertical position of the gypsum 

 with regard to the edges of the beds of the schistose metalliferous rock. 



