84 M. Brocham on the 



that I do not pretend to generalise, but which should not 

 apparently be entirely rejected, at least with regard to a 

 part of the gypsums of the Alps. 



- ■ ' ' 8. Other localities of Gypsum. 



■■ I have confined myself to describing the gypsums that 

 have fallen under my own observation. Having been occu- 

 pied so many years with this kind of rock, it may be im- 

 agined that I have consulted several works containing de- 

 tails on its mode of occurrence. I might therefore multiply 

 quotations, bring forward numerous facts, and, by discussing 

 them, add new proofs in support of the opinions I have 

 already expressed in the examination of each locality ob- 

 served ; but I do not wish to extend the limits of this memoir. 

 I shall content myself by observing that all the other facts 

 that I have been able to collect with regard to the gypsums 

 of the Alps, (at least between the Mont Cenis and St. Go- 

 thard) may be arranged under three heads : 



1. Those that are at the surface, and which do not appear 

 to contain any bed of a foreign substance. The greatest 

 number are of this kind ; from this circumstance has often 

 arisen the idea that those gypsums were the remains of an- 

 cient deposits in narrow basins. 



2. Those which alternate with well characterised transi- 

 tion rocks, principally with argillaceous slates. 



3. Lastly, those that are considered as primitive. I have 

 seen but one example of it quoted (besides those of Cogne 

 and St. Gothard, which I have described above); it is in 

 the Haut Valais, near Lachs. I have not been able to ob- 

 serve it, having had no knowledge of it before ray last 

 tour. 



From what I know relatively to this last, it does not ap- 

 pear that it is from a decided alternation with primitive 

 rocks that it has been referred to that formation, but solely 

 because it contains mica in tolerable quantity, and in suffi- 

 ciently continuous veins ; a character altogether insufficient, 



