572 SUPPLEMENT. 



stance also remarked by Dolomieu, who says that 

 such granites differ from those of the mountains y 

 as the grains are larger, the substances less inter- 

 woven and coherent, while each has a greater ten- 

 dency to regular crystallisation. But, on the 

 other hand, Charpentier observed, in various parts 

 of Saxony, veins of granite in mountains of gneiss ; 

 the granite consisting of white quartz in very small 

 grains, mica in fine particles, while the felspar was 

 scarcely distinguishable from the quartz*. 

 Slips. The slips or dykes found in coal mines, may 



also be classed among the veins of stone. They 

 chiefly consist, as already mentioned, of basaltin 

 and basalton, clay-rock, and argillaceous sand- 

 stone. 



But the denomination of veinstones has been 

 more strictly confined to the substances found in 

 metallic veins, which, from their confined nature, 

 perhaps more properly belong to lithology ; whence 

 only a few observations are here offered, by way 

 of supplement to a treatise on rocks ; as they 

 often perplex the learner, and sometimes even the 

 adept, by combinations which do not occur irt 

 mountain masses. A short account of these vein- 

 stones, given by an honest practical miner, may 

 Account by not be unacceptable. " What I call veinstone, 



Williams. 



* Ib. No. 16, p. 22. 



