« .•:'(*) 



:) 



ILLUSTRATIONS OF THE 



-^ 



t 



fuch horizontal flratific 

 depofition from water, 



as is the efFecl of 



d we llioLild 



per 



marks of the materials having been introdu 



ed with violence 



their pi 



Th 



e 



tuniits cannot objed to the trial of 

 by thefe two fa6ls. 



Nep. 



leory 



As to the firft, it is acknowledged, that there 

 is a certain regular difpofition of the fubllances 

 in mineral veins, as flated § 59, but it is one 

 which has hardly any thing in common with 

 the real phenomena of flratification. It con- 

 lifts in the diftribution of the principal fiibftan- 

 ces in coats parallel to the fides of the vein, each 



fubftanc 



e forming a feparate coat. 



In a 



vein, 



for inftance, containing quartz, fluor, calcareous 

 fpar, lead, 8cc. we might exped to find a lining 

 of quartz cryftals, applied immediately to the 

 v/alls of the mine, and following exaclly the 

 irregularities of their furface ; next, perhaps, 

 a coat of fluor, then of calcareous fpar, and laft of 

 lead-ore in the centre of the vein, the fame or- 

 der being obferved on the oppoiitc fide. Thefe 

 fucceflive coats, it is material to remark, are not 

 in planes, but in uneven furfaces, of which the 

 inequalities are evidently determined by thofe 

 of the walls, that is, of the rock which forms 

 the fides of the vein ; neither are they horizon- 

 tal, but are parallel to the walls, whether thefe 

 be perpendicular or inclined. Here, therefore, 



. . there 



