450 W. A. E. USSHER ON THE CHRONOLOGICAL VALUE 



Beche * furnish another example of the excessive amount of Post- 

 cretaceous denudation to which the country has been subjected. 



(e) The sands skirting the Bovey valley and resting in a con- 

 formable mantle on its slopes have been briefly described by Mr. 

 "Woodward f . They were formerly regarded as of Cretaceous age. 

 Bits of flints have been occasionally found in them. 



(0 Up on Straightway Hill, near Ottery St. Mary, De la Beche $ 

 gives a section of pebble-gravel exhibited in one of the pebble-bed 

 pits, either the result of decomposition in situ or of early fluviatile 

 redeposition. 



Thus far I have noticed deposits whose sites indicate a period of 

 formation disconnected with the present lines of drainage. 



B. (a) In all the broad valleys of Devon patches of gravel occur, 

 capping hills here and there or resting on their projecting slopes. 

 These are often fragmentary, and exist only as soils ; but in many 

 places gravels occur at heights exceeding 50 and sometimes 100 feet 

 above the neighbouring alluvia §. Such gravels are to be found in 

 Exeter, Tiverton, near Wellington, Stoke, Cannon, and many other 

 places. 



At lesser heights than 30 feet above the alluvia, terrace-like gra- 

 vels are occasionally exhibited. Near Ottery St. Mary two old 

 gravel terraces are visible. At the ' Blue Ball ' Inn, in the valley 

 of the Sid, in the Exe valley between Bickleigh and Exmouth, in 

 the Axe valley near Axminster &c, gravel deposits flank the alluvial 

 flats in places and gently slope down to them. On the Triassic cliffs 

 several patches of old river-gravel are exposed between Dawlish and 

 Budleigh Salterton, belonging to a period in which the sea-board 

 and inland contour were very different, though undergoing those 

 modifications which led to their present relations. 



Many of the small brooks of Devon are bordered by considerable 

 alluvial flats || far from the present main arteries of drainage. 



(6) Thick deposits of Postmiocene clay are found in the Bovey 

 valley ; at Petrockstow whitish and pale grey clays have been found 

 to extend to a depth exceeding 70 feet. 



Near Barnstaple Mr. Maw % notices the occurrence of tough 

 smooth brown clay, 78 feet in thickness, superimposed on a gra- 

 velly beach similar to that exposed at Fremington, the surface 

 of the clay being at an elevation of 100 feet above the sea at 

 Eoundswell, between Eremington and Tawstock. In Tawstock 

 Park the same observer noticed from 25 to 30 feet of clay on shingly 



* Eeport on the Geology of Cornwall and Devon, p. 249. 



t Quart. Journ. Geol. Soc. vol. xxxii. No. 127 (Aug. 1876), p. 230 ; also in 

 • Geology of England and Wales,' p. 317. 



} Eeport &c, p. 236. 



§ Vide paper by B. Parfitt, Trans. Dev. Assoc, for 1876, p. 162. 



|| R. A. C. Godwin- Austen, " Geology of S.E. Devon " (Trans. Geol. Soc. 2nd 

 ser. vol. vi. p. 439). 



% "Ona Supposed Deposit of Boulder-clay in Devonshire " (Quart. Journ. 

 Geol Soc. vol. xxi. pp. 447) ; Geol. Mag. vol. ii. p. 473. 



