236 Dr. PiTTON on the Strata below the Chalk. 



Three nearly parallel lines of fault, running about north and south, are especially remarkable in 

 Mr. De la Beche's Map ; one on the east of the county, passes from about a mile north of 

 Combe Beacon, through the hill which bears that name, along the valley of Warabrook, and the 

 streamlet west of Chardstock, across the Axe, to a point about two miles east of Axminster ; the 

 total extent to which it has been traced being about ten miles. A second fault extends from 

 Balay Down on the north of Challenge, through Membury, to the bed of the Yart south of 

 Yetlands ; the lias being thrown up into immediate apposition with the green-sand through a 

 great part of its course, as is also the case in the preceding fault near Warabrook. A third and 

 shorter fissure, about three miles in extent, reaches from the north of Wilmington to Stockers, 

 about two miles south of Widworthy, crossing the main London and Exeter road, and skirting the 

 eastern slope of an outlying hill of chalk on the south of that village. 



(120.) The hills which have furnished the greater number of the Black- 

 down fossils form the western range of the group between Honiton and 

 Wellington, about six miles to the south of Beacon Hill above mentioned. 

 Their escarpment, between Punchey Down on the north, and Upcot Pen on 

 the south, is distinguishable at a great distance by the white line produced 

 by the refuse thrown down from the openings of the sithe-stone pits; the 

 heaps thus formed constituting an almost continuous horizontal stripe in 

 the face of the hill. 



The whole thickness of the sandy strata above the red marl in this part of 

 the country, seems to be about 100 feet. The contrast between the barren- 

 ness of the upper sands, and the comparative fertility of the marl beneath, is 

 everywhere very conspicuous; and it would seem from the unequal ascent of 

 the hedge-rows and cultivated ground that the surface of the marl is very 

 uneven. 



The strata which afford the whetstones are about 80 feet below the top of the hill, to which 

 they are parallel. The mines (or " pits " as they are called) are driven in direct lines into 

 the hill, almost horizontally, and in some cases to considerable distances. The stony masses 

 from which the sithe-stones are cut, are concretions of very irregular figure, imbedded in looser 

 sand, nearly resembling those which occur in the upper division of the Lower green-sand near 

 Sandgate (21.): and though very irregular in shape, marks of the stratification of the sand can 

 be traced on their outside. The masses of which the sithe-stones are made, vary from 6 to 

 about 18 inches in diameter, and the beds which aflTord them would form a total thickness of about 

 7 feet, of which about 4 are fit for that purpose ; the looser stone at the top and bottom being 

 employed for building. 



The following is a sectional list of the beds in one of the principal sithe-stone pits at Punchey 

 Down, which, 1 was informed, was a fair representative of the whole : 



Ft. In. Ft. In. 



1 . Reddish sand rock, extending upwards to the top of the hill. 



2. " Fine vein ". Concretions of firmer consistence ; the best for sithe-stones. i 



[Shells are found in all the strata here, but abound remarkably in this one, fO 2 to 1 

 and in the '* rock " beneath it] J 



3. " Top sand rock" ; sand with irregular concretions ; of no use 3 to 4 



