584 



furnished by carbonate of lime, he proposes a modification of that 

 theory, and suggests that the carbonic acid by which the lime is held 

 in solution in the mud, furnishes the acid, and perhaps indicates the 

 existence of an unstable sesquicarbonate of that substance. " Where- 

 ever," adds the author, " 1 have met with natron, or obtained de- 

 tailed accounts of its occurrence, muriate of soda and carbonate of 

 lime existed in the soil, and the natron was found on the surface of 

 the moist earth or mud," 



December 13. — Lieutenant Ouchterlony, of the Madras Engineers, 

 and the Rev. Christopher Erie, M.A., of Hardwicke Rectory, near 

 Aylesbury, were elected Fellows of this Society. 



A paper " On the Geology of the South-east of Devonshire ; " 

 by Robert Alfred Cloyne Austen, Esq., F.G.S., was read. 



The district described in this memoir, is included within the rivers 

 Exe and Dart, and extends from the coast to the granitic region of 

 Dartmoor. 



The formations of which it consists, are first noticed, then the 

 faults, and, lastly, the probable amount of effects produced at each 

 period of disturbance. 



1. Formations. — These are considered under two heads : — 1st. ac- 

 cumulations produced by actual causes ; 2ndly, those produced by 

 causes in operation before the most recent disturbances, including 

 tertiary, secondary, transition, and igneous deposits. 



The first of these subdivisions contains a description of the shingle, 

 sand-hills, estuary deposits, and peat-bogs ; but the south-east of 

 Devonshire presents no phenomena connected with them, deserving 

 of particular notice. 



Tertiary Deposits. — ^To this class Mr. Austen assigns the («.) 

 raised marine deposits in estuaries, and (b.) raised beaches ; (c.) the 

 accumulations of water- worn rocks in valleys ; (d.) the Bovey de- 

 posit ; (e.) ossiferous caves ; and (/.) the bed of angular chalk flints, 

 and chert on Haldon and Blackdown. 



{a.) Raised Marine Estuary Deposits dSQ considered to exist in the 

 valleys of the Axe and the Otter, because those rivers, in their 

 present state, could not have accumulated the sediment which forms 

 the surface of the valleys, or have worn the vertical cliffs by which 

 they are partly bounded. In the valley of the Exe, above Topsham, 

 is a bed abounding with marine shells of existing species, but high 

 above the reach of any tide. 



(b.) The raised beaches of Hope's Nose and the Thatcher were 

 described by the author on a former occasion * ; but in this paper 

 he shows, that similar deposits occur to the west of Bovey-head, and 

 at intervals along the whole southern coast of Devonshire. The 

 upper limit of these beaches seldom exceeds 60 or 70 feet above the 

 present sea-level. The raised beach to the west of Bovey-head, 

 consists of shingle and indurated sand, associated, in the upper part, 

 with red haematite, and it is overlaid by a thick mass of the same 

 ore. This haematite is connected with the Upton iron lode. 

 * Proceedings, vol. ii. p. 102. 



