312 
THE GEOLOGIST. 
pendicular joints clearly developed, the angles where exposed being 
only slightly weathered, and the horizontal beds, if thick, standing 
out with well-defined edges and ends ; if thin, with sharp projecting 
edges, giving to the side a serrated appearance, rock-basins are 
scarcely ever found. When, on the contrary, the tor is rounded, the 
sides sloping or smooth, projecting beds not frequent or bold, and 
such beds as do project for the most part rounded at the edges, 
rock-basins will very frequently be found. For the above reasons 
Mr. Ormerod considers that in this district the rock-basins were 
caused by atmospheric action, that power working gently but surely 
upon the rock, and equally forming every description of basin, be 
it large or small, deep or shallow ; this he considers the rotation of 
pebbles could not do. 
The direction of the longest diameter is in nearly one-third of the 
cases from north to south, and in all but five out of the thirty-five 
cases is from the north-westerly to the south-easterly quarter : the 
cause of this Mr. Ormerod has not been able to discover. Although 
the direction of the longest diameters is in the greater number of 
instances towards the points, between which the perpendicular joints 
of the granite of Dartmoor generally range, he has not found that 
there was any connexion between them, the direction of the longest 
diameters rarely corresponding with that of either the main or cross 
joints on the same tors ; neither do the directions of the basins on 
the same tor always agree. The most violent storms on Dartmoor 
come from between west and south-west ; although occasionally 
heavy gales occur from the south-east, the winds from between the 
south and east are generally mild, and those between the north and 
north-west are not of frequent occurrence. The direction, therefore, 
of the longest diameter cannot be assigned to the action of the 
strongest or most prevalent winds." — Quarterly Journal Geol. Soc, 
vol. xiv., pages 22, 23. 
