03.4 Xatural Ilistorij. [Chap. IIL 



kinds of mineral bodies, as basalik masses, calce^ 

 denies, spars, SsC. 



That the inequalitij of decUvify exhibited by the 

 sides or flanks of mountains, in every part of the 

 globe, had any regard to the points of the eompasSy 

 seems to have been fn'st remarked by the celebrat- 

 ed Swedish geologist, Tilas*: but he seems rather 

 to have directed his views to the elevation or de- 

 pression of the surface of Sweden, than to the bear- 

 ings of the declivities of mountains in general, 

 Bergman first discovered, that the declivities of the 

 flanks of mountains bear an invariable relation to 

 their different aspects. He found that, in moun- 

 tains extending from north to south, the western 

 flank is the steepest, and the eastern the gentlest ^ 

 and that, in moimtains \\ hich run east and west, 

 the southern declivity is the steepest, and the 

 northern the gentlest. After Bergman, Buffoii 

 took notice of the generality of this phenomenon; 

 but his remark was confined to the eastern and 

 western sides of mountains extending from north 

 to south, having no reference to the north and 

 south sides of those which run east and west. The. 

 same fact was afterwards observed, in a general or 

 more partial manner, by Hermann, DclametheriCj^ 

 Torstcr, Pallas, and several others. 



'J'owards the close of the century. Air. Kirwan 

 directed his attention to this subject, and endea- 

 voured to assign the cause of this almost universal 

 allotment of unequal declivities to opposite points,, 

 and \\\\y the greatest are directed to the west and 

 south, and th(^ gentlest to the east and north. He. 



•* Sec Memoirs of Stockholm for l/DO. 



