ON ERRATIC CLOCKS OR BOULDERS. 193 



the denudation which is taking place. In a field near Red-Hill Farm, be- 

 tween btafFord and Stone, is one of the largest boidders of the district. This 

 boulder was not noticed until some twenty years ago, when it was found to 

 obstruct the plough, although still some depth underground. The obstruc- 

 tion became more and more serious each year, until a few years ago, when, 

 because of this impediment, the field was turned from an arable to a grazing 

 one. At this time the boulder rises about one foot above the level of the 

 field. The part exposed measures 6 feet by about 5, and evidently extends 

 under the turf for a much greater distance. This boulder is composed of 

 the grey granite of which so many other boulders in the neighbourhood 

 consist. 



" The boulders consist mainly of white granite and of felstone ; but many 

 other rocks occur, as may be seen by inspecting the specimens collected. In 

 the neighbourhood of Tettenhall there is a large percentage of granite boul- 

 ders ; but south of here there are very few indeed, the boulders being mainly 

 of felstone. In the Harborne district only one granite boulder has been 

 observed, while there are a hundred or so boulders of other rocks. The 

 contrast between the immense accumulation of granite boulders in the 

 Wolverhampton district and their comparatively small size and rarity around 

 Birmingham is most remarkable." 



Granite Boulder on the shore of Barnstaple Bay, North Devon, 



Mr. Pengelly reports the following particulars respecting this boulder, 

 upon which the raised beach on the northern side of Barnstaple Bay rests. 



So far as it is visible, it measures 7'5 x 6 x 3 ft., and therefore, containing 

 upwards of 135 cubic feet, cannot weigh less than 10 tons. 



It appeal's to have been first described by the late Eev. D. Williams, in 

 1837, as " flesh-coloured, like much of the Grampian granite " and, in his 

 opinion, " neither Lundy, Dartmoor, nor Cornish granite." 



In 1866 Mr. Spence Bate, believing that very similar granite existed in 

 Cornwall, expressed the opinion that it was not necessary to go so far as 

 Aberdeen, but that some transporting power must have been required to 

 bring it even from the nearest granite district, and that it without doubt 

 occupied its present position before the deposition of the beach resting 

 upon it. 



Recently Mr. Pengelly has been informed that red granite occurs on 

 Dartmoor, and therefore has no disinclination to say, with Mr. Bate, that we 

 need not go as far as Aberdeen to find the source of the boulder, although it 

 nevertheless may have come from the Grampians. 



Assuming that the block may have come from Lundy, twenty miles towards 

 the west, or down the valley of the Torridge from the nearest point of Dart- 

 moor, thirty miles off as the crow flies, its transport in either case must have 

 been due to more powerful agencies than any now in operation in the same 

 district. Between Barnstaple Bay and Lundy there are upwards of 20 fathoms 

 of water, a depth at which no wave that ever entered the Bristol Channel 

 would probably ever move the finest sand. 



Again, as the highest part of Dartmoor is but 2050 ft. above mean tide, 

 a straight line from it to where the boulder now Hes would have a fall of 

 1 in 77 only, down which the Dartmoor floods would certainly not transport 

 a rock upwards of 10 tons in weight. 



The foregoing considerations apply, of course, with at least equal force to 

 the hypothesis of any more distant derivation. 



That such a block might have been brought from Dartmoor down the Tor- 

 1873. 



