a Theory of the Earth. ^^^ 



6. jSTature of the covering of the veins, or thofe parts of 

 the vein next to the fubftaiice of the mountain. 



7. Nature of the drafts, or cryflalUfed geodcs contained in 

 the vein. 



7. A. The form, diiTlenfions, and nature of the mountain 

 which contains the vein. 



8. Situation of the vein in regard to the ftrata of the 

 mountain ; under what angle it interfefts them. 



9. Its fituation in regard to the exterior part of the moun- 

 tain ; whetlier it be parallel to the external inclination of 

 the mountain, or whether that inclination be in a contrary 

 direction. 



10. The progrefs of the vein : whether it be fubjeift to 

 change its direftion or fituation, and according to what 

 laws ; if there are any indications that precede thefe changes j 

 any corners, vacuities, or fiffures, which interrupt the courfe 

 of the vein ; and how it is found after having been loft : 

 fituation and difl;ance of the place where it is richeft. 



1 1 . Lateral veins or ramifications of the principal vein ; 

 veins by which it is accompanied, or which run parallel to it* 



12. To verify Werner's theory in regard to veins, the 

 fundamental principles of wliich are as follows : — - 



A. That the fpaccs occupied by veins have been orio-i- 

 nally empty crevices or fiffures. 



B. That thefe fifiiires have been afterwards filled from the 

 bottom upwards, at a time when the fea ftill covered the 

 mountains ; and by the precipitation or cryftallifation of the 

 fubftances which were before diflolvcd in the waters of the fea. 



C. That of two veins eroding each other, the moft mo- 

 di;rn is that which interfects the other. 



D. That of two veins, one of which flops and diverts the 

 courfe of the other, the moft modern is the latter. 



E. That, in the fame vein, the parts neareft to the fides of 

 the furrounding fubftance, iha fdluinde for inftance, are the 

 moft ancient J thofe in the middle the moft modern ; and 

 the intermediate ones of a mean antiquity. 



Vol. IV. A a F. Alfo 



