6 A Reply to Mt. Plajfalr's RefleSlions on 



" It is indeed worth while to compare what is faid conccmfng 

 the degradation of mouutains in the above quotations (from 

 m.y Geological Eflays) with what is advanced concerning 

 their indefrru6libility in another paflTage of the fame volume, 

 namely, all mountains are not fubject to decay ; for inftance, 

 fcarce any of thofe that confill of red granite, &c. One can 

 he at no lofs about ellimating the value of a fyltem in which 

 luch grofs inconfidencies make a nece{lar\' part." Mr. Play- 

 fair then rinds a grois inconiillency in maintaining that yo?«^ 

 mountains are fubjeA to decay, though all mountains are 

 not ; fafts proved beyond the reach of contradiftion ; but he 

 can fee none in his own two paragraphs. 



Page 157, " The quantity of hornblende and filiceous 

 fchidus nt-ceflliry to be dccompofed in order to produce ihg 

 coal ftrata prefently exifting, is enormous. It is true tliat 

 Mr. Kirwan, never at all embarraffed about preferving .1 fimi- 

 litude between nature as flie now is, and as (lie was hereto- 

 fore, lays it down, that the part of the primeval mountains, 

 v> Inch is worn away, contained much more carbon than the 

 part which is left behind : this, however, is an arbitrary fup- 

 pofition." Not quite arbitrary neither. Moimtains before 

 the flood mult have been in many refpefts difl'erently cir- 

 cumrtanced from the prefent; and if at prefent, after attain- 

 ing their utmoft (late of conlolidation, many of them are in 

 a itate of decay, much more liable to it muft they have been 

 then. Hornblende and filiceous fchifti are not the only 

 ftones that contain carbon, nor are the mountains that pre- 

 fent thefe rocks the only mountains that contain veins of it : 

 many granite mountains alio prefent them. Mr. Plavfair, 

 indeed, pays little regard to the authorities I adduce to prove 

 the fafls I allege ; more impartial readers may poffibly pay 

 more. 



I fliall therefore quote one entitled to the higheft credit. 

 Citizen Plaiiy, in the third volume of his Mineralogy, p. 308 

 and 309, tells us that anthracite (native mineral carbon loaded 

 with (lony matter) belongs exclufively to primitive countries, 

 and that the obfervaiions of Mr. Dolomieu prove the exill- 

 ence of carbon independently of animals and vegetables ; and 

 that anthracite was, he prefumcd, nothing more than pure 

 carbon, ailociated, by accidental caufes, with a certain quan- 

 tity of iron and filex. And Mr. Duhamel has fliown in a 

 memoir, approved by the Academy of Sciences, that the ar- 

 gillaceous Jirata that intercede beds of coal are formed of the 

 4clr'itci of the neighbouring mountains : Journal da Mines, 

 viii. p. 40; and Haiiy, iii. p. 319. My fyflcm is not then 



quite 



