310 
THE GKOLOGISr. 
Ormerod, who have treated of these phenomena in the papers 
ah-eady referred to. On the top of Haytor there are traces of two 
or more of these shallow basins (fig. 9). They are enumerated by 
Mr. Ormerod in his Table of Tors and Rock-basins, op. cit., p. 26. 
We cannot do better than quote at length some of Mr. Ormerod's 
observations on the foi-mation of rock-basins, whence the reader 
may learn much respecting the physical character of the Dartmoor 
granite. 
" Sir Henry de la Beche in a note on the * Report on Cornwall, 
Devon, and West Somerset' (p. 452), writes: — 'Dr. M'Cullocli has 
suggested that the friction of the quartz and felspar-fragments not 
unfrequently found in rock-basins may have contributed to deepen 
them. As we have often observed these fragments in motion dui-ing 
high winds, both when the basins were dry, or a small quantity of 
water in them, we are inclined to believe that this may the case.' 
The fragments occur in most basins ; in some, the bottom is covered 
by them. Rolled stones similar to those which occur in the ' pot- 
holes' have not been found by Mr. Ormerod in any basin, but the 
contents generally consist of small angular fragments of quartz and 
felspar, and schorl, which sometimes cover the bottom of the basin. 
Small lumps of granite occasionally are found, not rolled, but that 
have apparently fallen in where the sides are much weathered and 
falling to decay. Although in the habit of inspecting the basins in 
every state of the weather, from the mildest breeze to the heaviest 
storm, Mr. Ormerod had never seen these particles blown about in 
the water in the basins having the bottoms flat and sides upright, 
and had only seen them moved in shallow concave basins when dry, 
or when a heavy gale had blown them out together with the water. 
The cause suggested by Dr. M'Culloch could not affect the deep 
basins, as in those cases the particles would be undisturbed by 
motion of the water from wind. These small fragments, however, 
throw some light on the manner of the formation of the rock-basins. 
The granite of the Dartmoor district is in a great measure porphy- 
ritic ; it is for the most part of a large coarse grain, and schorl in 
variable proportions frequently occurs ; globular nodules, varying 
from an inch to upwards of a foot in diameter, often occur. These 
vai-y much ; sometimes they are harder than the adjoining rock, 
