464 Mr. Austen on the 



and on the north side is inclined to the north, or conforms to the slopes of the hill. 

 There is no ambiguity here respecting the stratification of the limestone, as it is 

 made very apparent by alternating seams of good anthracite, though cleavage 

 planes dipping south also traverse both limestones and slates ; the Dartington 

 limestone, at its west extremity, pitches down on the edges of the subjacent slate. 

 The limestone of Yalberton, though it has all the appearance of being included in 

 the grauwacke series, is found, when traced towards the Dart, not to dip with the 

 slates and sandstones exposed in that section, but to have thinned away on the 

 surface close to the village of Stoke Gabriel. In the same manner the great cal- 

 careous mass of the south and west of Torbay terminates in inconsiderable beds of 

 shaly limestone, along an E. and W. Une from Galmpton Creek towards Brixham, 

 by Churston Ferrers, and of which there is a good section at Galmpton. 



The termination of the great calcareous group of S.E. Devon, where it is ex- 

 posed in the coast-section at Sharkham Point, is represented in the accompanying 

 woodcut. 



Fig. 12. 



Termination of the limestone group (a) of South Devon, at Sharkham Point. 



Along their N. and W. edges these limestones set on, either as a capping to the 

 slate, when they often present a wall or low escarpment to the north, or they rest 

 against the south slopes of the ridges and low hills of slate, as at Bradley ; they then 

 dip with the slope, but carry the edge of each constituent bed of limestone to the 

 level of the crest of the ridge of slate. This is perhaps the most remarkable fea- 

 ture of these masses, and may be seen about Denbury and East Ogwell : whatever 

 the angle of dip may be, or however far the succession of beds may be carried 

 on, in a given linear direction, the upper surface forms a table-land. It is also 

 the case with the lower limestone of Ashburton and that of Plymouth. An ob- 

 server has only to ascend one of the higher slate hills in the vicinity of any of 

 these limestone masses to be assured of the fact here mentioned, and which serves 

 to connect all our limestone masses by one common feature. 



Any inquiry whence so large a quantity of calcareous matter was originally derived, though a ques- 

 tion of much geological interest, would be irrelevant in a mere local description ; but it may be observed, 

 that both in North and South Devon the existence of limestone appears in very many instances to 

 have depended on subaqueous volcanic disturbance, as it is interstratified with beds of compact and 

 ashy trap : thus the rock quarried at Leny near Launceston is a vesicular hornblendic mass, largely 



