[ 47 ] 



Again, the primeval mountains that run from E. to W. by 

 oppofing a fimiiar refiftance to the courfe of the waters from N. 

 to S. mufl have occalioned fimiiar depofitions on the northern 

 fides of thefe mountains againft which thefe waters impinged, 

 and thus fmoothed tliem. 



Where mountains interfedl each other in an oblique direction, 

 the N E fide of one range being contiguous to the S W. flanks 

 of- another range, there the afflux of adventitious particles on 

 the north eaft fide of the one, mufl: have frequently extended 

 to the S W. fide of the other, particularly if that afflux were 

 flrong and copious ; thus the Erzgebirge of Saxony, which run 

 from W. to E. have their N E. fides contiguous to the S W. 

 fide of the Riefer/gebirge that feparate Silefia from Bohemia, and 

 hence thefe latter are covered with the fame beds of Gneifs, &c. 

 as the northern fides of the Saxon, and thereby are rendered 

 fmooth and gentle comparatively to the oppofite fide, which 

 being fheltered, remains fteep and abrupt, which explains the 

 feventh obfervation. 



The caufes here afligned explain why the covering of adven- 

 titious ftrata on the highefl; mountains is generally thinnefl: at 

 the greatefl height, and thickefh towards the foot of the moun- 

 tain, for the bulk of the water that contained the adventitious 

 particles being proportioned to its depth, and the mafs of earthy 



particles 



