JONES — ON THE WEATHERING OF GRANITE. 
309 
"In the 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 
mountain, 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, 
p. 116. 
/' 
Lig:n. 9. — Outlines of Rook-basins on Haytor. 
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 natui-al formation, according to Dr. M'CuUoch and Mr. 
