DOMAIN I. SIDEROUS. 



conceives that what he calls petrosilex passes 

 into jasper, by the influence of the atmosphere ; 

 but in this he judges from the colours, and not 

 from the analysis. His primitive petrosilex, as 

 he declares, is felsite, while he places jasper, 

 which he calls primitive, after his secondary pe- 

 trosilex, which he expressly mentions is the 

 hornstein of Werner. There is therefore great 

 confusion in his context, as he derives a primary 

 rock from a secondary substance ; and his pe- 

 trosilex must be itself regarded as a dull and 

 imperfect jasper; nor is it inconceivable that 

 the surface may even attract more iron from the 

 atmosphere, where atoms of that substance con- 

 stantly float, as has appeared from many experi- 

 ments and inferences. The most beautiful jas- 

 pers of Siberia appear on the eastern side of the 

 southern part of the Uralian chain, particularly 

 the ribbon jasper, green and red, and that spot- 

 ted with pitchstone, or perhaps brown jasper. 

 Another beautiful kind presents, on a bright red 

 base, little undulating veins of olive green, ac- 

 companied by a white thread which follows all 

 the undulations. In Daouria, on the left bank 

 of the river Argun, one of the sources of the 

 Amur, there is a famous mountain composed of 

 green jasper; but, like the other kinds, it will 

 not rise in large pieces, but splits into smallfrag- 



