a Theory of the Earth. 357 



30. Whether It be rare to find, under the form of ftrata, 

 other metalHc mines than thofe of copper, iron, lead, cala- 

 mine, and manganefe. 



3T. Whether the mines in ftrata are generally poor near 

 the furface of the mountain, and become richer the deeper 

 they proceed. 



31. A. Whether mines, where the metal is found in 

 lumps or in a mafs {Jlockwerhe), ought to be clafled among 

 thofe in veins or thofe in ftrata * ? 



-2. In coal mines to obferve the nature of the coal ; more 

 or'lefs compad ; more or lefs rich in bitumen; more or Icfs 

 mixed with argil or pyrites. 



33. To examine, in the coal, the traces of their origin; 

 whether they have been formed of wood, turf, or marine 



plants f. 



34. To obferve whether there are found the remams of 



marine or terreftrial animals. 



35. Theprogrefs of the ftrata: whether it be true thai 

 they often begin by defcending in order to become hori- 

 7.ontal, and "afterwards to re-afcend ; and that they are 

 thickeft in the horizontal part, and give coal of a better 

 quality t- 



* 3,. B. To obferve alfo a third pofuion of the ore, or ore found in 

 the tranfuions (jlav.-fibcidu.!,); that is to fay, between two kind, of Rone 

 of a very different ..ature ; as between argillaceous fch.ft and calcareous 

 Itone between the fame fihift and compound rocks, &c. Not to con. 

 found this pofnion of ore with real veins, nor with metalliferous banks, 

 ore in ftrata, and x.\it flock'werke. C. ^ ^, , , , 



+ „ A To diftineuini carefully real coal from jet or foffil coal (the 

 h-aun.kobk of the Germans), and from coal earth, as well as from that 

 fubftance known by the Germans under the name of bknd-kohle. C. 



,3 B To examine whether there is not found fometimes m calcareous 

 foil, fat,"i:olatinous coal ; or whether there is never found but dry, friable 



coal. C. , . . 



+ 55. A. To afccrtain whether there cxifts fofhl coal m veins, as is 



fiid iv be ihc cafe at Wthruu in Upper Lufatia. C 



A a 3 36- ^Vhe^ 



