Vol. 60.] THE VALLEY OF THE TEIGN. 323 



For the date of our ancient surface we need not go farther back 

 than the close of the Eocene Period, because it is evident, from the 

 manner iu which the Teign crosses the Eocene of the Bovey Basin, 

 that its valley is of later date than the Eocene Period. We may 

 reasonably conclude that it was at the beginning of Oligo- 

 cene time that the present river-system of Devonshire 

 was initiated. 



I will next endeavour to picture the probable aspect of the 

 surface of this part of England in Eocene and Oligocene times, and 

 to estimate the extent to which it was then covered by Xeozoic 

 deposits. It is not necessary for our present purpose to consider 

 how far the Jurassic rocks may have extended over Devonshire, 

 because we know that they were subsequently truncated and over- 

 stepped by the Cretaceous strata ; but these latter have certainly to 

 be considered. 



We know that the sea of the Selbornian Sands (=' Upper Green- 

 sand') covered what are now the Haldon Hills, and must have 

 stretched to the borders of Dartmoor. The deeper sea of the 

 Upper Chalk must have covered a still larger area, and would have 

 covered the greater part of Dartmoor, unless the relative levels 

 of Dartmoor and the Haldons have been greatlv altered since 

 Cretaceous time, a contingency which is very probable. At the 

 close of the Cretaceous Period, the West of England appears to 

 have been raised above the sea-level, and the whole of Devonshire 

 must have been subjected to the detrition of subaerial agents 

 during the time represented by the break between the Cretaceous 

 and the Eocene and by the duration of the Lower Eocene Epoch. 

 That the granite of Dartmoor was then exposed we know, from the 

 frequent fragments of granite and tourmaline-rock in the Haldon 

 gravels. 



The Eocene subsidence at length carried the lacustrine area 

 of the Bournemouth Beds Avestward over the whole of Eastern 

 Devonshire and over the Haldon Hills, which rise to more than 

 800 feet above the sea. 3Ir. H. B. Woodward has recorded the 

 existence of deposits which closely resemble those of the Bovey 

 Basin between Axminster and Lyme Regis, at an elevation of 

 400 feet. 1 They consist of rough flint-and-chert gravel, fine white 

 sand, with white and mottled clays, and they are most probably of 

 Eocene age. Similar gravels and tracts of stony clay (mapped as 

 Clay-with-Elints) cap the tops of the many ridges which lead up 

 from the coastal cliffs to the Blackdown Hills, and they occur also 

 on these hills at levels of between 800 and 900 feet. Mr. W. A. 

 E. Ussher informs me that some of the patches of clay at such 

 levels near Otterford, Churchstanton, and Burnworthy not im- 

 probably include remnants of Eocene beds in situ. 



A plain prolonged westward from the summits of the Blackdown 

 Hills would pass over all the central part of Devonshire between 

 Dartmoor and Exmoor ; and as part of such a plain still remains 



1 Suram. Progr. Geol. Surv. for 1901. pp. 53-59 : and Rep. Brit. Assoc. 

 902 (Belfast) p. 601. 



