484 DOMAIN V. CALCAREOUS. 



should repose on large masses or divisions ; while 

 minute and broken lights only distract the at- 

 tention and the memory. The gypsous rocks 

 may safely be reduced to two kinds, the coarse 

 and the compact. 



Primitive. It was long conceived that gypsum was of 

 the most recent formation, till a rock of this 

 kind, undoubtedly primitive, was discovered by 

 Saussure in the Alps. Dolomieu indeed ex- 

 presses his wonder, that gypsum has not been 

 more frequently formed from primitive marble, 

 as the sulphuric acid might easily be produced 

 from the decomposition of pyrites. But the re- 

 marks of Saussure must not be omitted. 



" In regard to gypsum, it is found at St. 

 Gothard, either below Ayrol, as I have said, 

 1805, or in the Val-Canaria. It is in mass, of 

 a fine and brilliant grain; it does not effervesce 

 with acids, and consequently is free from all 

 calcareous mixture. 



" But what is more rare, is to find gypsum 

 in a schistose form, and mixed with thin layers 

 of mica: this contains some calcareous parts j 

 it slightly effervesces. 



" I do not think that this gypsous schistus is 

 a primitive rock, like the calcareous micaceous- 

 schistus ; I believe it to be of modern origin, 

 and that it originated by deposition in hollows, 



