©N THE DECLIVITIES OF MOUNTAINS. 265 



tercept the depofitions that do not furmount them, and thus 

 leave the internal ridges fteep on both fides. 



Hence, 6. low granitic or other primitive hills are fre- Low mountain* 

 quently uncovered by adventitious ftrata on all (ides, as at 

 Phanet in the county of Donegal, or are covered on all fides ; 

 the impregnated waters either ealily paffing over them, or ftag- 

 nating upon them, according to the greater or lefs rapidity of 

 its courfe, and the obftacles it met with. 



The twofold motion of the ancient ocean is noticed both by Remarks on the 

 Buffon and Bergman, but neither of them have deduced from £j£j^JJj ' 

 it the true explanation of the phenomena of which we here Uergmamw 

 treat : Buffon attributes the formation of fecondary mountains 

 to depofition or fediments from the fea after the exiftence of 

 fifh, 1. Epoques, p. 143, in 8vo. which he fays invefted the 

 bafes of mountains without noticing any diftin6tion of (ides, 

 p. 144 and 170. He thinks thefe fediments were equally con- 

 veyed from both poles towards the equator, for it is the 

 equatorial regions that he thinks thofe mighty caverns opened, 

 towards which the primitive ocean was impetuoufly borne and 

 in which it was ingulphed, p. 181, 182, and 183. If fo, 

 iimilar declivities fhould be formed on the fouthem as on the 

 northern fides of mountains, which is contrary to the obferved 

 facts. His explanation of the eaftern and weftern declivities is 

 defective and erroneous, for he attributes the abruptnefs of the 

 weltern fides to the erofion of the coafts on that fide (an ero- 

 fion that exifts only in fancy) and the fmoothnefs of the eaftern 

 to the gradual defertion and retreat of the fea on that fide, 

 p. 184. and 185, a retreat equally fictitious, as De Luc has 

 well (hewn. Whereas fince the general motion of the fea is 

 from E. to W. if the erofion were of either fide it fhould rather 

 be on the eaftern than on the weftern ; befides, if the gentle 

 declivities of the eaftern fides of mountains arofe from the gra- 

 dual retreat of the fea, the petrifactions of the fecondary moun- 

 tains thus formed fhould confift of fuch fhell-fifh as inhabit 

 (hallow feas or fhores, whereas they confift chiefly of thofe 

 called pelagicce, which inhabit the greateft depths *. 



With refpect to the eaftern and weftern declivities, Mr. 

 Bergman's account of the origin of their inequality agrees ex- 

 actly with mine, 2. Bergm. Erdeklotet § 183 and 187, but he 



* 2. Bergm. Erdekugel, p. 315, 



fails 



