go On the Declivities of Mountains. 



in geological refearches. In the prefent effay I (hall confine 

 myfelf to the inveftigation of one inftance of this fort, namely, 

 the inequality of declivity which the fides or flanks of moun- 

 tains exhibit, in every part of the globe hitherto examined, 

 according to the points of the compafs to which they face, 

 and are expofed. 



That one part of almoft every high mountain or bill is 

 fteeper than another, could not have efcaped the notice of 

 any perfon who had traverfed fuch mountains; but that Na- 

 ture, in the formation of fuch declivities, had any regard to 

 different afpects or points of the compafs, feems to have been 

 firft remarked by the celebrated Swedifh geologift Mr. Tilas, 

 in the 22d Vol. of the Memoires of Stockholm for 1760*. 

 Neither Varenius, Lulolph, nor Buffon in his Natural Hif- 

 tory publifhcd in 1748, have noticed this remarkable cir- 

 cumftance. 



The obfervation of Tilas, however, relates only to the ex- 

 treme ends, and not to the flanks of mountains : with refpe£t 

 to the former, he remarked that the Jlccpefl declivity always 

 faces that part of the country where the land lies loweft, and 

 the gentLjl that part of the country where the land lies 

 higheft ; and that, in the fouthem and eaftern parts of Ssve- 

 den, they confequently face the eaft and fouth-eaft, and in 

 the northern the weft. The effential part of this obfervation 

 extends therefore only to the general elevation or depreffion 

 of the country, and not to the bearings of thefe declivities. 



The difcovery that the different declivities of the flanks 

 of mountains bear an invariable relation to their different 

 afpecls, feems to have been firft publifhed by Mr. Bergman 

 in his Phyfical Defcription of the Earth, of which the fecond 

 edition appeared in 1773. He there remarked that, in 

 mountains that extend from north to fouth, the weftern flank 

 is the Jleepejl and the eaftern the gcntlefl : and that, in moun- 

 tains which run eaft and weft, the fouthem declivity is the 

 fteepeft, and the northern the gentleft. Vol. II. § 187. 



This affcrtion he grounds on the observations related in 

 his firft Vol. § 32, namely, That iftly, in Scandinavia, in the 

 Suevoberg mountains that run north and fouth, feparating 



♦ See alfoVol.XXV. Swed. Abhandl. p. 191, where Cronftedt ex- 

 plains fome obfeur* parts of Tilas's obligation. 



Sweden 



