a Theory of the Earth. 35 j 



tains ? And, if this circumftance be true, does it arife from 

 the relative age of thefe minerals and mountains, or from 

 the fubftance of the mountains favouring the precipitation 

 of one kind of mineral more than that of another ? 



17. Is it true, as M. deTrebrafays, that the richeft veins, 

 and the richeft points of any vein, are found in the vertical 

 line which correfponds with the Imved part of the refervoirs 

 of the rain water, and never in the peaks and moft elevated 

 ridges? And, if this be well afcertained, would it not prove 

 that the veins had an origin pofterior to the grand revolu- 

 tions which have given to the lurface of our globe its prefent 

 form, and that the metals have been depofited in them by 

 the meteoric waters ? 



18. Is it true alfo that the richeft mines are found in 

 mountains, the declivities of which are not fteep* ? 



19. Are there Inftances of veins, entirely exhaufted, being 

 again filled up \^ith ore? 



20. Does the produftion of metals depend on the influ- 

 ence of the fun and climate ? Are they more frequently found 

 near the eaftern or fouthern, than the weftern or northern 

 faces of mountains ? 



21. Can we gcneralife the obfervation made in Siberia, 

 Tranfylvania, at Mount Rofe, and in other places, that in 

 gold mines the veins are richer near the furface of moun- 

 tains than at a greater depth. 



21. A. Is it generally true, that the veins are richer at 

 t!ii ir points of interfe&ion than in any other place? 



22. Is the inclination of veins fecn more frequently con- 

 trary, than parallel to, the adjacent face of the mountain? 



23. Does it fometimes happen that the rock which forms 

 • the fides [neben-gejlein) of the vein is as rich and even 



richer in metal than the vein itfelf ^ and would it thence 



• As the Sjxon authors generally fay, becaufe the faft is true among 

 them and in fome other ccintrits, whili; the cafe is not fo clfevvhere, anrJ 

 pariJC'.ilarly In the Fyrtiicts. C. 



A a 3 follow, 



