57* tECTORE XLVI. 



diameter, and the greatest of them might be represented on a six inch globe 

 by a single additional thickness of the paper with which it is covered. 

 Mount Sinai in Japan, Mount Caucasus, Etna, the Southern Pyrenees, St. 

 George among the Azores, Mount Adam in Ceylon, Atlas, Olympus, and 

 Taurus are also high mountains: and there are some very considerable eleva- 

 tions in the island Owhyhee. Ben Nevis, in Scotland, is the loftiest of the 

 British hills, but its height is consideraljly less than a mils. (Plate 

 XXXVIII. Fig. 5iy.) 



The most elevated mountains, excepting the summits of volcanos, con- 

 sist of rocks, more or less mixed, without regular order, and commonly of 

 granite or porphyry. These are called primary mountains ; they run ge- 

 nerally from east to west in the old world, and from north to south in the 

 new; and many of them are observed to be of easier ascent on the east than 

 on the west side. The secondary mountains accompany them in the same 

 direction, they consist of strata, mostly calcarious and argillaceous, that is, 

 of the nature of limestone and clay, with a few animal and vegetable re- 

 mains, in an obscure form, together with salt, coals, and sulphur. The ter- 

 tiary, mountains are still smaller; and in these, animal and vegetable remains- 

 are very abundant ; they consist chiefly of limestone, marble, alabaster, 

 building stone, mill stone, and chalk, with beds of flint. Where the se- 

 condary and tertiary mountains are intersected by vallies, the opposite strata, 

 often correspond at equal heights, as if the vallies had been cut or washed 

 from between them, but sometimes the mountains have their strata disposed 

 as if they had been elevated by an internal force, and their summits had 

 afterwards crumbled away, the strata which are lowest in the plains being 

 highest in, the mountains. The strata of these mountains are often inter- 

 mixed with veins of metal, running in all possible directions, and occupying, 

 vacuities which appear to be of somewhat later date than the original forma- 

 tion of the mountains. The volcanic mountains interrupt those of every 

 other description without any regularity, as if their origin were totally in- 

 dependent of that of all the rest. 



The internal constitution of the earth is little known from actual observa- 

 tion, for the deptlis to which we "have penetrated are comparatively very in- 

 considerable, the deepest mine scarcely descending half a mile perpendicularUv 



