. 1858.] OEMEEOD EOCK-BASINS. 23 



probably be found or not. First, rock-basins are scarcely ever found 

 where it is the character of the Tor to have the perpendicular joints 

 clearly developed, — the angles, where exposed, being only shghtly 

 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. When, on the con- 

 trary, 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. 

 Por the above reasons, the Author considered 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 the 

 rotation of pebbles, he considered, could not do. 



The direction of the longest diameter is shown by the preceding 

 Table (p. 20) to be in nearly one-third of the cases from N. to S.,and in 

 aU but 5 out of the 35 cases to be from the north-westerly to the 

 south-easterly quarter : the cause of this the Author has not been able 

 to discover. Although the direction of the longest diameters is in the 

 greater number of instances towards the same points, between which 

 the perpendicular joints of the granite of Dartmoor generally range, 

 he had 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 W. and S.W. ; 

 although occasionally heavy gales occur from the S.E., the winds from 

 between the S. and E. are generally mild, and those between the N. 

 and N.W. 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. The Author, in conclusion, 

 acknowledges his obligations to Dr. Croker, F.G.S., for his aid in 

 pointing out the localities of certain basins. 



