Reports and Proceedings — Geological Society of London. 191 



running parallel to a dominant ridge, nor is it a simple combination 

 of one with the other, as often happens ; but it apparently consists 

 of parts of two transverse valleys linked by a longitudinal one. 



The Teign runs off Dartmoor through a gorge which takes an 

 easterly direction, as if it were going to join the Exe ; it is then 

 deflected southward into what, with respect to the Permian 

 escarpment, is a longitudinal valley ; this ends in a low-lying 

 plain, and from this plain it escapes eastward to the sea through 

 a transverse valley, which has been cut across the ridge of Permian 

 and Cretaceous rocks. 



Several attempts have been made to explain the anomalies of the 

 course taken by the Teign ; but none of them is satisfactory, because 

 the writers have not sufficiently considei-ed the probable conditions 

 of the surface on which the river-valleys were originated, or the 

 extent to which the older rocks around Dartmoor may have been 

 covered by Cretaceous and Tertiary deposits. 



The author considers these points, and concludes that in Oligocene 

 time a tliick mantle of soft Neozoic strata must have stretched across 

 Devon and the adjacent parts of the English Channel ; that this 

 mantle consisted mainly of Selbornian Sands and of the later Eocene 

 deposits, the latter overlapping the former and passing on to the 

 surface of the Palaeozoic rocks; further, that these Eocene deposits 

 covered all the central parts of Devon, and were banked up against 

 the northern, eastern, and southern sides of Dartmoor. He assumes, 

 moreover, that the post-Eocene elevation of the region gave this 

 surface a general easterly slope ; and consequently that, although 

 streams ran off Dartmoor in all directions, those which drained 

 eastward had the longer courses and passed from the moorland 

 area on to a plain, the drainage of which was directed eastward to 

 the shore of the Oligocene sea. 



The general direction of the Upper Teign where it flows over the 

 granitic area is east-north-easterly ; the direction of its gorge as far 

 as Clifford Bridge is nearly due east, and if the conditions were as 

 above described, the precursor of this river is not likely to have 

 followed the course of the present river beyond Clifford Bridge. 

 There is not likely to have been any ridge or obstacle that would 

 have deflected it so far to the southward, nor anything to prevent it 

 from continuing its easterly course towards, and probably across, 

 the valley of the Exe. 



The valley of the Lower Teign l^elow Dnnsford is not likely 

 to have existed in Oligocene time, but was part of the eastward 

 sloping plain ; the local drainage, however, may have been carried 

 by a little brook flowing southward or south-eastward to join the 

 river which was then initiating the valley of the Teign estuary. 

 The erosion of the present longitudinal valley out of the Paleozoic 

 rocks must have been accomplished in much later times, and was 

 probably due to the development of the Permian escarpment. 



The valley through which the Teign now flows from Newton to 

 Teignmouth traverses this escarpment ; and its excavation can only 

 be attributed to a stream that flowed eastward from higher ground 



