318 Bernani Mohson — Permian Breccias of S. Devon Coast. 



or 13-84 miles per hour. Penck assumes a specific gravity of 2-2, and 

 that of the quartz-porphyry may he taken as 13^^ per cent, higher; 

 but having made no deduction tor its irrcgnhir form in calculating its 

 contents, the result will he approximately correct, so that a current 

 of 14 miles an hour would move it from a horizontal surface. 

 According to Prof. F. Katzel ^ torrents may attain a velocity of 

 6 metres per second (21-G kilometres per hour). Sir A. Geikie'^ 

 says even the current " of a torrent does not exceed 18 or 20 miles 

 in the liour." It is therefore quite possihle that the block was 

 transported by water. 



IV. — The Mode of Formation of tub liuEcoiAS. 



Mr. W. Pengelly ^ seems to have regarded the breccias as due to 

 marine action. He says, ''The aggregation, however, does not appear 

 ■to be such as would have resulted from the action of a stream or 

 current ; it rather indicates the agencj' of waves on an open beach." 

 He also assumes that the beds were deposited horizontally, and not 

 inclined as in a delta face, for he gives ^ a table of 34 observed dips 

 from which he calculates the mean amount of dip at 15^° and the 

 mean direction between Saltern Cove and Flat Point (Straight Point) 

 as N. 44t^ E. true. From these data he calculates * that the thickness 

 between Goodringtoii Sands and Straight Point is four miles, to 

 which he adds H miles for the thickness between Straight Point and 

 Charton Bay. giving 5^ miles for the New Eed Rocks as a whole, 

 while Mr. Ussher •"' calculates the total thickness of the New Red 

 Rocks of Somerset and Devon at 3,280 feet, though he says 2,500 feet 

 appears a more likely estimate. 



Mr. Pengelly seems to have had some misgivings as to the beds 

 having been deposited horizontally, for he quotes' Sir Charles 

 Lyell's well-known description of inclined deltaic deposits at Monte 

 •Calvo, near Nice," but adds, " Possibly something of this kind may 

 have occurred in the formation of the Devonshire Trias; nevertheless, 

 1 am not aware of a single fact on which to base such an hypothesis." 



Mr. Jukes-Browne'^ quotes the same account from Lyell, and says 

 that " the coarse sandstones of Teignmouth and Dawlish, with their 

 angular fragments of local rocks, seem to be torrential deposits of 

 this kind." 



In the account of the "Excursion to Newton Abbot, Chudleigh, 

 Dartmoor, and Torquay " '" there occurs the following passage with 



' " Die Erdo uml das Lcbeu" (1902), vol. ii, p. 86. 

 - "Textbook of Geolosjy," 3rd ed. (1893), p. 376 : 4th ed. (1903), p. 487. 

 ^ "The Red Sandstones, Conglomerates, and Marls of Devonshire," part ii: Ann. 

 Kept, and Trans. Plymouth Inst., 1862-3, p. 31. 



* Log. cit., p. 29. 



* Same paper, part iii (1864-5), p. 40. 



^ "Ontlie Triassic Kocks of Somerset and Devon": Quart. Journ. Geol. Soc, 

 1876, p. 392. 

 ■" Loc. cit., p. 45. 



•* "Elements of Geology," 6th ed. (1865), p. 18. 

 9 "The Building of the British Isles," 2nd ed. (1892), p. 168. 

 '" Proc. Geol. Assoc., vol. xvi (1900), p. 434. 



