42 ON THE GENERAL DISPOSITION OF THE 



pursue questions of this nature, which at present seem 

 to lead to no useful geological results, but which may 

 be recorded with propriety among the independent 

 facts that belong to physical geography. 



The term mountain is of very vague signification ; 

 and, however generally limited to a certain scale of 

 altitude, that scale is rather regulated by comparison 

 than by a fixed rule. The hills of Tweedale would ex- 

 cite far different sensatfons in the plains of Poland, 

 and at the foot of ./Etna ; and, to the shepherds of 

 the Valais, the elevations of Gogmagog would be in- 

 visible. Of a conventional and variable term, no defi- 

 nition can be given ; nor is it required. 



The sudden ascent of a very high mountain from a 

 plain is rare ; and, except in the case of some of the 

 volcanic mountains, it is scarcely known. As moun- 

 tains gradually descend in altitude they become hills ; 

 and thus it is also a necessary consequence, that hills 

 formed of elevations gradually diminishing, should in- 

 tervene between the higher lands and the plains. The 

 arrangements of such hills with respect to the higher 

 mountains which they accompany, is partly regulated 

 by the nature of the rocks and the position of the 

 strata, and partly by the water courses which have fur- 

 rowed them and removed the materials that once con- 

 nected them more intimately together. But it is 

 chiefly in the higher elevations that the asperities pro- 

 duced by naked and protruding rocks are found. 

 The effects of the atmosphere, the power of rain and 

 frost, far most active in these elevated regions, con- 

 spiring with the force of gravity, demolish that which 

 can find no resting place on the steep declivities, and 

 thus leave naked and bare those pinnacles and preci- 

 pices which, with different views, form alike the study 

 of the painter and the geologist. 



