462 



ON THE STRONTIAN 



portunity of making, prove that the general and 

 particular mineraiogical relations of the clay-slate 

 of Scotland, agree with those of the clay-slate of 

 Hungary and Saxony. Humboldt and Sonnen- 

 schmid have ascertained the identity of the clay- 

 slate of North and South America, with that ob- 

 served in different parts of Europe ; and the 

 investigations of Pallas, Patrin, and others, have 

 shewn, that the mineraiogical relations of the 

 clay-slate of Asia, are similar to those of the clay- 

 slate of Africa, and that these agree with those 

 observed in the clay-slate of Europe and Ame- 

 rica. 



In like manner, it has been observed, that the 

 formations of ores follow nearly the same general 

 law as the formations of rocks. Thus the ninth 

 lead-glance formation, which is composed of lead- 

 glance, poor in silver, with radiated pyrites, rarely 

 with a little blende, and accompanied with heavy 

 spar, fluor-spar, calc-spar and quartz, is found in 

 Derbyshire in England, in Saxony, and in Swe- 

 den ; and in these different countries it contains * 

 the ores and earthy minerals just enumerated. 



The eighth lead- glance formation, which con- 

 sists of lead-glance rich in silver, yellow blende, 



* See Dr Charles Anderson's excellent translation of 

 Werner's admirable Treatise on the Origin and Forma- 

 tion of Veins * 



