390 W. A. E. TJSSHER ON THE TRIASSIC 



represented by replacing sandstones. In close proximity to those 

 localities where the Lower Division seems entirely absent we have 

 pointed out at least two* considerable faults affecting the junction 

 of the Trias with the older rocks, and shown the numerous disturb- 

 ances displacing the members of the Trias ; so that, though there 

 is a possibility of the Lower Division being absent altogether in one 

 or two places, facts seem to point to its elimination by faults or 

 concealment by the Lower Marls. 



Economic Uses. — At Woodcock's Well, west of Collumpton, and 

 Cowley Moor, north of Tiverton, bands or lenticular masses of clay 

 occur in the Lower Sandstones, and afford material for brick-making 

 in both those places. 



At Langford (Langord on Ordnance Map), near Upton Pyne, 

 brecciated sandstones have been worked for manganese. Breccias 

 and sands at Luckham, stained blackish, have been worked for iron- 

 ore. In two brick-pits near Montle Grand, in Exeter, clay and 

 brecciated clay are used for brick-making, the shale-fragments being 

 burnt in the brick, which is hard and rough. 



The breccias of Heavitree, Lnckham, and Sampford Peverell are 

 quarried for building-purposes, and, in the last-mentioned place also 

 for burning lime, owing to the contained limestone. 



Thickness. — Here, again, we are at a loss in forming an estimate 

 of the thickness of the division as exposed in the south coast. In 

 the first place, there is a probability of at least a hundred feet of 

 sandstone being cut out at Exmouth ; in the next, though many 

 high dips are to be seen in the beds between Exmouth and Torquay, 

 my friend Mr. H. B. Woodward assures me that they are in many 

 cases due to faults, and that the beds are in numerous instances 

 comparatively horizontal ; it is also evident that the coast-line 

 cannot represent their thickness, as it crosses the line of dip 

 diagonally, so that, instead of 10 miles from Exmouth to Torquay, 

 we must take 7 miles between Exmouth and Chudleigh. Starting 

 with a fault, and the probability of several more occurring, but not 

 to be traced, owing to homogeneity of beds traversed or variability 

 of the division, any attempt at estimating their thickness would be 

 very untrustworthy. 



South of Exeter the area occupied by this division has a breadth 

 of from 6 to 8 miles ; north-east of Exeter about 3 miles, two of 

 which may be taken as occupied by tolerably horizontal Lower 

 Sandstones, and the lower beds as concealed. The broadest part of 

 the Crediton valley occupied by these beds is 3|- miles ; but, both on 

 the north and south side of the valley, they appear to dip away from 

 the older rocks, forming a synclinal trough, the sandstones at Upton 

 Pyne, on the south side of the valley, apparently concealing breccias. 

 The axis of depression is a little to the north of Bramford Speke f. 



* At Horridge Down, south of Wiveliscombe, and at Canon Leigh, near 

 Westleigh. 



t This synclinal axis seems to pass into the Culm-measure area on the south- 

 west of Newton St. Cyres. West of St. Cyres the Trias in the Crediton valley 

 is almost exclusively composed of breccia containing numerous fragments of 

 igneous rocks, 



