326 MR. A. J. JUKES-BROWNE OX [Aug. I904, 



another : the one slope was easterly, and the other was southerly ; 

 the latter is now the dominant slope, and consequently I think that 

 it is of later date than the other. This hrings us to consider the 

 question of the courses which the ancestors or precursors of the 

 Teign and other Dartmoor streams are likely to have taken. 



We shall begin with the Upper Teign. That part of its course 

 which lies through the granitic area of Dartmoor was doubtless 

 marked out at a still earlier period, and was only being more 

 deeply incised during Oligocene time. In all probability, also, 

 the further part of its course, which is now stereotyped as the 

 deeply-cut ' gorge of the Teign,' was initiated in Eocene time, 

 and at a level far above that of the existent parallel ridges. But 

 somewhere this high-level surface of Palaeozoic rock passed beneath 

 a superjacent, gently-sloping mass of Eocene deposits. So far as 

 my argument is concerned, it does not matter whether the mantle 

 of Eocene beds spread on to the granite, or whether it thinned out 

 at lower levels : at some point in its upper course the precursor of 

 the Teign left the surface of the older rocks and passed on to that 

 of the Eocene beds ; and the general trend of this surface we believe 

 to have been towards the east. 



We arrive therefore at the conclusion, that beyond the confines 

 of Dartmoor the drainage-system of Oligocene time was established 

 upon the surface of the Eocene beds, and consequently that this 

 drainage-system was afterwards transferred from the Eocene 

 to the Palaeozoic surface. "We cau also see that the courses of 

 the rivers may have been profoundly modified in the process of 

 transfer, not only by their encountering rocks of varying hardness 

 in the Palaeozoic complex, but also by the influence of powerful 

 earth-movements. 



If, then, the Teign continued its course over Eocene beds, and if 

 their surface sloped eastward, it is not likely that the river at that 

 time followed its present anomalous course ; it is probable that it 

 took a much more direct line towards, and possibly across, the 

 valley of the Exe. The general direction of the Upper Teign, 

 including the Xorth Teign as the main tributary, is from west- 

 south-west to east-north-east ; near Sandy Park it changes to 

 nearly east; while at Clifford Barton it bends to the south-east, and 

 passes into what may be called the Lower Teign at Dunsford. 

 My theory is that at this early period the valley of the Lower 

 Teign had no existence, but was part of the plain which sloped 

 gently eastward from Dartmoor across what are now the Haldon 

 Hills, and that there was nothing to prevent the Upper Teigii 

 from continuing its easterly course ; so that it may have joined 

 or received the Exe (then a much shorter stream) somewhere about 

 the position of Exeter. 



The country to the north and south of the Teign gorge, between 

 Sandy Park and Clifford Barton, maintains a high level, rising to 

 over 1100 feet on the south side and to nearly 900 feet on the 

 north side : while the highest parts of the country, between Cliiford 



