1869.] ORMEROD DARTMOOR GRANITE. 279 



rocks near the Teign north of Moreton, and the Parson's Brown Loaf 

 near Lustleigh Eectory. 



In noticing the effects that bedding, joints, and spheroidal struc- 

 ture have had, and now have, it has been necessary to touch on each 

 separately ; but it is scarcely needful to say that these three causes 

 are constantly acting together. The action of joints in dividing the 

 masses which have since become isolated, and of decay penetrating 

 between the stratiform blocks, have doubtless shaped the rocks that 

 form the Cheese Ring and similar places. To the joint action of all 

 three causes may probably be attributed the Logan or Kecking Stones 

 of the east of Dartmoor, at Belstone, and Thornworthy, and to that of 

 bedding and joints, probably, that on Rippon Tor ; the stones that 

 form these three Logans are probably in situ. The Drewsteignton 

 Logan in the Teign is of compact, hard, angular felspathic granite, 

 and rests upon granite ; it is in the Carbonaceous district, about a 

 quarter of a mile to the east of the point where the Dartmoor 

 granite ceases : it is not in situ ; and the amount of large felspar 

 crystals contained in the stone lead to the opinion that it has not 

 formed part of any of the numerous granite and elvan veins which 

 in that locality penetrate the Carbonaceous rocks. The well-known 

 " Nutcracker," the Logan in Lustleigh Cleave, is on the side of the 

 hill, and is not in situ ; it is apparently a block of granite which has 

 rolled down from above and fallen into a position in which it could 

 be easily moved. This Logan was wantonly thrown out of balance a 

 few years since, but has now been replaced. Another Logan of 

 similar character is almost close to the " Nutcracker." A further 

 examination has shown that the rocks at Leigh Bridge described by 

 the author at p. 419 of vol. xxiii. of the ' Quarterly Journal ' as 

 " masses of granite piled on each other," are in situ. This appear- 

 ance is due to the north and south lines of joint and spheroidal 

 structure. 



In this paper attention has been directed solely to the bed- 

 ding, joints, and decay from spheroidal structure which appear in 

 times past to have been, and which now are, active agents in pro- 

 ducing the disintegration of the granite, of which the effects are so 

 apparent; doubtless the varied manner in which the rocks have 

 been acted upon arises in a great degree from the peculiar mineralo- 

 gical character of each district ; but this is a point on which I much 

 regret that it is not in my power to give reliable information. 



It has been needful occasionally to go over ground which has 

 already been partly described by others ; and in those cases it has 

 been endeavoured to incorporate the opinions and observations of 

 the various authors in their own words. 



Discussion. 



Prof. Ansted had observed similar conditions in Leicestershire, 

 Alderney, and elsewhere. The most important feature in the case 

 was the amount of subaerial disintegration and denudation to which 

 the rocks, and especially the Tors, bore witness. The bedding 



