114 ME. A. J. JUKES-BBOWNE ON THE AGE AXD [May I907, 



Permian strata to the underlying Palaeozoic rocks. The surface 

 thus produced may be called ' the basal plane of the Eocene Series/ 



It would seem, therefore, that the Eocene was the earliest epoch 

 at which the plateaus of the Torquay area could have been formed. 

 On the other hand, the special features and the present condition of 

 the plateau-area make it unlikely that its surface dates from a much 

 later period of the Earth's history. 



The special facts are that the plateau-area has been dissected and 

 trenched by several deeply-cut valleys, that these valleys all drain 

 southward, and that one of them (the Ilsharn valley) cuts through a 

 ridge which is higher than the plateau on which it rises. These 

 circumstances lead me to conclude that the existing drainage- 

 system has been transferred from a vanished surface high above the 

 present one. Such a surface would have been that of the Eocene 

 deposits which were raised into land during Oligocene time. Con- 

 sequently, the theory that the plateau-area is a remnant of the 

 basal Eocene plane is in harmony with all the facts of the case. 



Post-Eocene Flexures. 



if the higher parts of the Torquay plateau-area are remnants of 

 the basal Eocene plane, we are naturally led to enquire how this 

 plane came to occupy its present position, and what relations exist 

 between it and the other known portions of the same surface. 



In the first place, it is clear that the plateau near Torquay is not 

 a regular continuation of the Haldon-Hill plateau, for if outline- 

 sections be drawn through existing summit-levels it will be seen 

 that the one could not pass into the other. The base of the Eocene, 

 as drawn on the map of the Geological Survey, runs at about 700 

 feet on Little Haldon, and considering the fact that no remains of 

 Eocene or of Greensand occur on Great Hill west of "Watcombe Park, 

 which reaches 580 feet and is the highest point on the watershed 

 between the Teign and Torbay, it is evident that the base of the 

 Eocene must have passed over this ridge at a level of more than 

 600 feet. Indeed we are likely to be under the mark in putting it 

 as low as 650 feet. Now, Mincent Hill (340 feet) is only about 

 half a mile south of Great Hill, and there is consequently a drop of 

 about 300 feet from one plane to the other within this distance 

 (see fig. 2, p. 109). 



Again, a little to the eastward and starting from the lower plane 

 at Petitor, the height of which (about 335 feet) accords with the 

 level of the plateau in the northern part of St. Mary church, there 

 is a rapid northward rise to 422 feet in a quarter of a mile ; and on 

 the north side of the Watcombe valley the ground rises to 500 feet 

 on the watershed-ridge. 



It will be remembered that there is a similar steep slope on the 

 west side of Little Haldon, where a space of about a mile with a 

 fall of some 300 feet intervenes between the high plateau capped 

 by Eocene gravel and the lower slope on which patches of the 



