20 EXISTENCE OF MECHANICAL DEPOSITS. 



It may perhaps be alledged, that thofe mountains of Cum- 

 berland and Tweedale are not the primary mountains, but 

 compofed of the fecondary fchiftus, which is every where 

 known to contain thefe objects belonging to a former earth. 

 Naturalifts who have not an opportunity of convincing them- 

 felves by their proper examination, muft judge with regard to 

 that geological fact by the defcription of others. Now it is 

 moft fortunate for natural hiftory, that it has been in this range 

 of mountains that, we have difcovered thofe marks of a marine 

 origin ; for, I fhall afterwards have occafion to give the clear- 

 eft light into this fubjecl, from obfervations made in other parts 

 of thofe fame mountains of fchift, by which it will be proved 

 that they are primary ftrata ; and thus no manner of doubt will 

 remain in the minds of naturalifts, who might otherwife fuf- 

 pect that we were deceiving ourfelve-s, by miftaking the fe- 

 condary for the primitive fchiftus. 

 Remark that the Dr. Hutton's account of the mountains in the fouth of Scot- 

 primitive, ^ and 1S confufed and unfcientifical, and hardly comes within 

 the pale of true geognofia. It is not my intention, at prefent, 

 to enter into an examination of his obfervations ; the object of 

 this poftfcript is to (hew, that the limeftone between Noble 

 Houfe and the Crook Inn does not belong to the primitive 

 for it lies be- mountains. The beds of limeftone mentioned by Sir James 

 mnfiJion'flatf- Ha!I ' l obferved ¥ n g between ftrata of tranfition flate, and 

 alternating with this flate alternating with ftrata of grey wacke ; confequently 

 ftrata of grey the w hole belongs to the tranfition clafs of rocks. 

 Defcription of The limeftone has a blueifh grey colour, fracture is foliated, 

 the feveral rocks, the diftincl concretions are from coarfe to fine grained, and it 

 is hardly tranflucid on the edges. It is often traverfed by 

 veins of calcareous fpar, and fometimes it contains thin beds 

 of flinty flate (Kiefel Schiefer of Werner). The tranfition 

 flate has a blueifh or fmoke grey colour, has generally lefs 

 luftre than the primitive flate, and contains much interfperfed 

 mica. I obferved it in all the ftages from nearly pure flate to 

 grey wacke. The grey wacke is compofed of fragments of 

 : tranfition flate, flinty flate, and quartz, connected by a bafis 

 of tranfition flate. It is frequently traverfed by veins of 

 quartz, and is to be obferved where the fragments are hardly 

 diftinguifhable from their fize ; it has much the appearance of 

 a breccia. I fhall take another opportunity of fending you 

 drawings of the different kinds of petrefaclions that occur in 

 the limeftone. 



IV. A 



