Yol. 6^.~] OEIGIN OF THE PLATEAUS ABOUND TORQUAY. 115 



gravel are again found from 400 down to 120 feet, before coming 

 to the main tract of the Bovey Eocene. Both cases are susceptible 

 of the same explanation , namely, that the steep slopes are portions 

 of the basal Eocene plane which have been sharply deflexed by 

 subsequent earth-movement. 



It should also be noted that the Torquay plateau lies to the 

 south-east of the Bovey basin, and that the general direction of this 

 basin is from north-west to south-east, so that a line drawn from 

 the valley of the Bovey, south of Lustleigh, through Newton Abbot 

 and Aller Yale, would, if prolonged, pass through the Plainmoor and 

 Babbacombe plateau. I have elsewhere x indicated the probability 

 that this axis of depression was prolonged to the north-west across 

 Dartmoor to Hatherleigh and Marland in North Devon. I now 

 suggest that the line of flexure may have been continued in the 

 opposite direction to the south-east. 



On the old supposition that the Bovey area is an isolated lake- 

 basin, it is not easy to understand how so small an area could be so 

 deeply depressed below the general surface of the surrounding- 

 country, for the inward dips prove it to be a deflexed area. But, if it 

 is part of a prolonged synclinal trough, it becomes more intelligible, 

 because we know that such troughs or axes often consist of a series 

 of elongate or boat-shaped depressions, some of which may be deep 

 while others are shallow. There is, therefore, nothing to be surprised 

 at in the occurrence of a specially deep basin along a line of general 

 deflexion. 



Moreover, the detailed mapping of the Geological Survey seems 

 to indicate that the so-called ' Bovey basin ' is not a single basin, 

 but a double one ; for the Newton- Abbot and Aller-Yale area is 

 separated from the main basin by a ridge of Devonian slates with 

 igneous intrusions, which runs through Highweek and Knowles 

 Hill and appears to pass eastward under the alluvium of the Teign, 

 since similar rocks emerge again at the head of the Teign estuary 

 on both sides of the river. It is, of course, possible that this ridge 

 was in existence before the deposition of the Eocene beds, but the 

 way in which these seem to be pinched out at Newton Abbot is 

 very suggestive of the idea that there are really two basins. 



Connexion between the Aller Basin and the 

 St. Marychurch Plateau. 



If reference be made to the Geological-Survey map (Sheet 339), it 

 will be seen that the south-western slope of Milber Down, on which 

 the Eocene gravels are dipping into the Aller basin, is actually 

 continuous with the steep watershed of the Torquay area near 

 Watcombe. The heads of the Aller, Hatchcombe, and Barton brooks 

 have eaten deeply into the ancient slope, and have destroyed not 

 only the original mantle of Eocene gravels and sands, but have 



1 Quai t. Journ. Geol. Soe. vol. k (1904) p. 330. 



