Mr. Austen on the Geology of the South-east of Surrey. 65 



Dr. Heifer to be composed of granite and gneiss ; and the northern 

 and middle parts of the country to consist of transition slates and 

 limestones. The country south of the Maulmain river, the province 

 of Ye, towards Tavoy, is a sterile slate district covered with bamboo. 

 Amherst province presents isolated ridges of limestone with fertile 

 land at their bases : to the south are sandstones and conglomerates. 

 Tertiary formations, chiefly argillaceous, occupy the higher parts of 

 Amherst and Ye provinces, the plains of Tavoy and Kalleevung, those 

 between Tavoy and Poilon, the valley of Jaun-biank and of the Te- 

 nassirim river, and the elevated land of Meta-mio. 



In 1837 Dr. Heifer discovered tin near lake Loadut, about 110 

 miles N.N.E. of Maulmain, and in 1840 he reported the country to 

 the north of the Pakehan river to be the richest stanniferous district 

 within the Tenassirim provinces : the ore is found in the debris of 

 primitive rocks, and the range is stated to be a continuation of the 

 Siamese tin district of Rinowng. Domel island and the banks of 

 the Boukpeer are also cited as localities yielding tin. 



Capt. Tremenhere's account of the tin of the Tenassirim provinces 

 is, that it occurs chiefly in the beds and banks of those rivers which 

 issue from the primitive mountains : on the Thengodong river, in 

 the immediate vicinity of the coal mines on the Great Tenassirim 

 river, 11,889 grains of peroxide of tin were collected in an hour and 

 a half. Along the courses of the streams which flow into the Little 

 Tenassirim river it occurs in thin beds, in gravel ; and Capt Tremen- 

 here calculates, from a short trial he made, that two men could ob- 

 tain by washing the gravel about 5 lbs. 2 oz. 464 grs. of tin per day. 



At Kalian, on the right bank of the Great Tenassirim river, eleven 

 miles from Mergui, Capt. Tremenhere found a vein of tin about 

 three feet and a half wide, nearly vertical, and included in a white 

 decomposing granitic rock. The ore is described as equal to that 

 from Banca. It is conjectured that tin may ultimately be found in 

 the small isolated granitic hills which rise out of the alluvial plain 

 in the neighbourhood of Kahan. 



April 5. — A paper was read " On the Geology of the South-east 

 of Surrey." By R. A. C. Austen, Esq., Sec. G.S. 



The observations embodied in this paper relate to certain points 

 regarding the structure of the district on either side of the North 

 Downs of Surrey, to the number and order of the component forma- 

 tions, and the evidences which they present of the conditions under 

 which they were formed. 



Mr. Austen regards the steep walls of the chalk formation as 

 forming a more obvious physical boundary of the Wealden formation, 

 especially on the south, than the great escarpment of the greensand. 

 He remarks that the subdivisions of the eocene tertiary present lines 

 of escarpment corresponding to the secondary series. He maintains 

 that the Wealden in its present state is not a valley of elevation, — 

 that at some former period it has been an elevated area, but that 

 subsequent changes in the relative positions of the earth's crust have 

 reduced the elevation which this particular portion must have had at 

 a given time, and with reference to other circumjacent areas. 



Phil. Mag. S. 3. Vol. 24. No. 1 56. Jan. 1 844. F 



