304 DOMAIN IV. TALCOUS. 



which seems peculiar to it, that of preventing pas- 

 sengers from seeing those within the apartments, 

 while these perfectly discern objects without. A 

 second kind of this glass is less esteemed, which, 

 though found in plates of a foot square, is spotted 

 with yellow, red, green, and blue; and conse- 

 quently is not used as the former. It might be 

 called mica variegata."* 



In the Swiss Alps a beautiful talc is found, of a 

 changeable green, on silvery white, with thin leaves 

 forming contorted masses, adhering to a magne- 

 sian rock. Talc also occurs in leaves of various 

 sizes, from half an inch to six or twelve inches, 

 in granitic rocks, where it supplies the place of 

 mica. When not larger than mica, it is here 

 called micarel, genuine mica being ranked among 

 the siderous substances. Mr. Kirwan has given 

 the name of talcite to a parasitic substance, in 

 the form of small scales, loose, or slightly co- 

 herent, 

 chalk of The gradation of the involved or contorted talc 



Jinati^on. 



of Swisserland, to the chalk of Brian^on, or of 

 Dauphiny, is sufficiently apparent. The latter is 

 used by the French tailors in marking the shapes 

 on broad cloth, whence the name of chalk has 



* Molina, Stor. Nat. del Chili, p. 77- The French translation 

 is very inaccurate. 



