236 Reports & Proceedings — Geological Society of London. 



2. February 26, 1919.— Mr. G. W. Lamplugh, F.R.S., President, 



in the Chair. 



The President said in accordance with the Special Notice it was 

 proposed to change the subject previously announced for the after- 

 noon's meeting, and he hoped the change would be approved, namely, 

 that Colonel T. W. Edgeworth David, D.S.O., C.M.G., D.Sc., F.R.s"., 

 would deliver a lecture on "Geology at the Western Front"-. 



After the lecture a vote of thanks was unanimously accorded to 

 Colonel David for his lecture. 



3. March 12, 1919.— Mr. G. W. Lamplugh, F.R.S.. President, 



in the Chair. 



The following communication was read by Mr. R. D. Oldham, 

 F.R.S., in the absence of the author: — 



"The Early History of the Indus, Brahmaputra, and Ganges." 

 By Lieut. Edwin Hall Pascoe, I.A.R.O., M.A., D.Sc, F.G.S., 

 Superintendent Geological Survey of India. 



The occurrences of marine Nummulitic rocks show that in Eocene 

 times a gulf of the sea extended up the Indus valley and the hill 

 country to the west of it, and eastwards along the southern margin of 

 the Himalayas at least as far as the neighbourhood of Nairn Tal. In 

 the Himalayan region the marine deposits are succeeded by a series 

 of red clays with intercalated sandstones and occasionally marine 

 beds, regarded by the author as having been deposited in a series of 

 lagoons. The tipper Tertiary deposits consist of a great series of 

 conglomerates, sandstones, and silts of freshwater origin, which are 

 known to extend along the whole of the southern face of the 

 Himalayas. From these geological indications the author concludes 

 that the first effect of the commencement of the Himalayan uplift 

 was the establishment of a great westward-flowing river along the 

 southern face of the range, for which he proposes the name of 

 Indobrahm. The distribution of Tertiary rocks on the northern 

 side of the range suggests that here also a westward-flowing river 

 was formed, which discharged either round the end of the range into 

 the same sea as the Indobrahm, or flowed westward into the region 

 of Turkestan and the Caspian Sea. The subsequent history of the 

 drainage system consists of the capture of the upper waters of this 

 river by a tributary of the Indobrahm, a cutting-back along the 

 valley to form the eastward flowing Tsangpo, now the upper waters 

 of the Brahmaputra, and the capture of the lower reaches in part by 

 the Sutlej and in part by the Attock tributary of the Indobrahm, to 

 form the Himalayan portion of the Indus valley. Meanwhile, on the 

 southern side of the range, some of the tributaries on the eastern side 

 of the Lower Indobrahm had cut back from the Sind region and cut 

 off the original bend near Attock, to form the present plains of the 

 Punjab ; and farther east, a river cutting back along the present line 

 of the Gangetic delta and lower course of the Ganges and 

 Brahmaputra, had captured the upper waters of the Indobrahm to 

 form the present Brahmaputra. The same system of capture had 

 worked westwards, until the tributaries of the Indobrahm had been 



