JONES — ON THE WEATHERING OF GRANITE. 



309 



Iq tlie upper part of Aberdeenshire I have observed that the 

 granitic mountains are very remarkable for their extreme sterility 

 and the desolate aspect that they present. The summits are 

 rounded, sometimes nearly flat, to a great extent, and entirely 

 covered by disintegrating blocks and stones, together with gravel and 

 sand. Some of them present protuberances, consisting of granite 

 much decomposed, forming tabular masses, intersected perpen- 

 dicularly by fissures, and evidently portions of the mass of the 

 momitain, which have either originally protruded beyond the surface, 

 or have resisted disintegration. Most of the mountains exhibit per- 

 pendicular precipices near the summit, which generally assumes the 

 circular form, constituting the hollows named " corries," and having 

 a lake at their base. The rock near the surface, wherever it is ex- 

 posed, has split into tabular masses, generally pretty regular, and 

 exhibiting the appearance of strata, intersected by rectangular 

 fissures. The true nature of these tables, however, is really under- 

 stood on examining the precipices, where they are best seen, and 

 where, notwithstanding, the perpendicular fissures more resemble 

 the seams of strata. There is no tendency in any part to the con- 

 centric or globular arrangement, nor do the masses in decomposing 

 ever present that appearance." — Manual of Geology, 2nd edit., 1844, 



An interesting feature observed in a large portion of the Dartmoor 

 district is the occurrence of rock-basins, or shallow hollows on ex- 

 posed surfaces of the granite, often on the summit of the "tors." 

 These are of natural formation, according to Dr. M'Culloch and Mr. 



p. 116. 



Lign, 9. — Outlines of Rock -basins on Haytor. 



