GEOLOGY 



At Exeter remains of old gravels of the Exe rise to over loo feet 

 above the alluvium. It is rare to find any more or less continuous ex- 

 tension of the older gravels in the Secondary area and still more so in 

 the Palseozoic area. Good examples of gravels at various levels mark 

 stages in the excavation of the Dart valley* above Totnes. In the 

 Teign valley many instances have been described.'' On a Culm sand- 

 stone quarry south of Bideford an old gravel of the Torridge was observed 

 at about 70 feet above the adjacent alluvium. A good example of more 

 recent gravel is visible at 10 feet above the alluvium of the same river at 

 Beam Bridge, north-west of Torrington. The best terrace features of the 

 Taw are in the vicinity of Umberleigh ; of the Tamar at and north of 

 Rumleigh House, opposite Calstock ; of the Tavy north of Lopwell ; 

 of the Plym between Shaugh Bridge and Bickleigh Bridge ; of the Avon 

 at Avonwick and South Brent ; of the Erme between Keaton Bridge and 

 Ivybridge. All these indicate a comparatively recent stage in the exca- 

 vation of their respective valleys, although in some cases they occur at 

 50 to 100 feet above the adjacent alluvia. The stream valley deposits 

 bear out the remark of Godwin-Austen." ' There is not perhaps a single 

 valley through which a river or even a brook at present takes its course, 

 along which alluvia are not found at elevations such as the existing 

 streams in their most swollen state never have attained.' 



Raised Beaches. — The raised beaches rest on rock platforms at eleva- 

 tions which nowhere indicate a depression of 100 feet and seldom of 

 more than 20 to 30 feet. The raised beach under the Hoe is described 

 by Hennah * as from 2 to 3 feet of cemented sand and water-worn 

 pebbles from 1 5 to 18 feet above high water mark. Dr. Moore gives 

 the height of the Hoe raised beach as 35 feet above high water. 



Between Prawle and Start Points the steep slopes are fringed by a 

 strip of ground, 40 to 1 20 yards wide, composed of Head or stony clay, 

 sloping gently seaward, from heights of 50 to 100 feet, to the cliff line 

 which is formed by it for about 3 miles. The accumulation shows signs 

 of admixture with old beach material in places at its base, which rests 

 on a well-defined rock platform a few feet above high water mark. 

 Upon this platform at Malcombe Point two large water-worn erratic 

 boulders rest. In view of the boulders at the base of the Saunton 

 raised beach it is more probable that these were stranded during the 

 raised beach period than from the ballast of a wreck. The Head is 30 

 feet thick or more in the cliffs. 



The raised beach at the south horn of Hope's Nose consists of 

 stratified shelly sand, with pebbles and shells in the lower part, and its 

 base, according to Godwin- Austen,* is 3 1 feet above high water mark. 

 Old beach materials rich in shells are scattered over parts of reef platforms, 

 at 10 to 20 feet above high water mark, on the Thatcher rock. Hunt° 



1 Ussher, 'On some Old Gravels of the River Dart,' etc., Trans. Devon Assoc. 1876. 

 * Ormerod, Siuart. Joum. Geol. Sac. vol. xxiii. p. 423, etc. 

 ' Trans. Geol. Soc. ser. 2, vol. vi. p. 439. * Op. cit. ser. i, vol. iv. p. 410. 



^ Op. cit. p. 441. 



° Hunt, 'The Raised Beach of the Thatcher Rock,' etc., Trans. Devon Assoc, 1888, pp. 225-52, 

 I 41 6 



