Oct. 4, 1883] 



NATURE 



555 



I shall have to refer to it further on. This is very clearly 

 defined by a gneissic axis on its southern margin, against which 

 the secondary rocks rest, and by a more northern line of the same 

 primitive rock-, succeeded by another of isolated low hills follow- 

 ing the northern base and the course of the Brahmaputra, and 

 generally lying to the north of it. The last outcrop is seen at 

 Dhoobri, and thence it is no doubt continuous across the delta 

 to similar outer ips of Bengal gneiss on the Ganges, thus connect- 

 ing this axis of elevation with that of peninsular India. The 

 above range is convex to the south, curving up to the N E. in 

 the Lhota Naga and Nowgong Hills, and to the W.N.W. in 

 the Garo Hills. 



The Burrail range forms another subsidiary line of elevation 

 to the above from the Naga Hills to Jaintiapnr, and falls away 

 dipping under the Sylhet Mils, 1 to reappear at the most S.YY. 

 point of the Garo Hills. From its highest point in the Naga 

 Hills (Japvo), where the strata become nearly horizontal, it 

 merges into and throws off the high N. and S. ridges that bound 

 the Munipur valley on the west, to join the Lushai Hills on the 

 south. This I would call the Western Munipur and Arakan 

 range. It has no granitoid axis ; but to the N.E. of Munipur a 

 great mass of intrusive rock occurs at the high peak of Shurui- 

 furar, and thence a high line of elevation runs N.N.E. to 

 Saramethi Peak, and to the south forms the eastern boundary of 

 the Munipur valley, and might be called the eastern Munipur 

 range — it is the water-parting between the above valley and that 

 of the Kyangdweng. 



We car, in a measure, exemplify the structure of the Himalaya 

 by that of the bones of the right hand, with fingers much 

 elongated and stretched wide apart, of which the wrist and back 

 may represent the broader belt of granitic rocks of the eastern 

 area, the thumb and fingers the more or less continuous ridges of 

 the N.W., some less prolonged than others to the north-west, 

 such as the Chor axis, which may be represented by the thumb, 

 terminating on the southern margin near the Sutlej. The left 

 hand placed opposite will represent the same features to the 

 west of the Indus. We will even carry this simile further, and 

 as a rough illustration suppose the intervals or long basins 

 between the fingers to be filled with sedimentary deposits, and 

 the fingers then to be brcught closer together, producing a 

 crushing and crumpling of the strata. At the same time an 

 elevation or depression, first of one or more of the fingers, then 

 of another or of the whole hand has taken place, and you are 

 presented with very much what has gnne on upon a grand scale 

 over this vast area. As these changes of level have not taken 

 place along the whole range from E. to W. in an equal 

 extent, but upon certain transverse or diagonal lines, undulations 

 more or less great have been the result, and some formations 

 have attained a higher position in some places than in others, 

 producing, very early in the history of these mountains, a trans- 

 verse system of drainage lines, leading through the long axial 

 ridges. 



The last efforts of these rising, sinking, and lateral crushing, 

 and, as I believe, very slowly aciing forces, are to be seen at the 

 southern face of these mountains in the tertiary strata that make 

 up the Sub-Himalayan axis (Sivalik) a topographical feature 

 w hich is most striking by reason of its persistence and uniformity 

 for some 1600 miles ; for, although a similar and synchronal 

 elevation of the Alps has taken place, the same regularity of 

 orographical features has not been the result, most probably 

 from the difference in the original outline of deposition in the 

 latter area. One object in this address w ill be to endeavour to 

 point out and compare some of the physical features of the two 

 great European and Asiatic chains. 



From Assam on the east to the Punjab on the west, bending 

 round and extending to Scinde, this fringing line of parallel 

 ridges is found at the base of the Himalayas, sometimes higher, 

 sometimes wider, often forming elliptical valleys. Only in one 

 part of the belt east of the Teesta are they absent altogether, 

 and for a distance of fifty miles the metamorphic rocks ri e 

 directly from the plains of India, 2 a feature representing a great 

 break — the correct interpretation of which will tell us very much 

 of the past hi-tory of these mountains. These formations are of 

 vast thickness, and in the Punjab, where they attain their 

 greatest width and elevation between the Chenab and the Indus, 

 cover an area of 13,000 square miles. 



The whole of this material has been derived from the adjacent 

 Himalayas, representing many feet of the older and higher 



1 "BAM" or "jhii" — Hind., a marsh. 



liu-in-Austen, /. A. S. B. 1867, p. 117. Memoirs 0/ the Geological 

 Society 0/ India, Medlicott, vol. iv. pp. 392 and 435. 



mountain ranges, and has travelled down valleys that have been 

 excavated in pie-tertiary times. This points to a slow subsidence 

 of the whole southern side of the mountain mass, deposition 

 generally keeping pace with it, broken off by recurring long 

 intervals of re-elevation. Such important, well-marked features 

 as these cannot be omitted when treating of a mountain system. 

 Many long and instructive pages of it- history are written on these 

 rocks, with the help of which we may reconstruct some of the 

 outlines of its more ancient geography. 



The next most interesting feature connected with the former 

 distribution of land and sea is that these .Sub-Himalayan forma- 

 tions arc fresh-water, or torrential, showing that since nummulitic 

 or eocene times the sea has never washed the base of the 

 Himalayas. ' In fact, there is no evidence of this from the gorge 

 where the Ganges leaves the mountains up to the base of the 

 Garo Hills ; pointing to an extension northward at that early age 

 of the Arabian Sea, separated from the Bay of Bengal by penin- 

 sular India. I am led also to believe that from Assam to Scinde 

 there once existed one continuous drainage line, a great river 

 receiving its tributaries from the Himalayas, partly a land of 

 lakes and marshes, the home of that wonderful mammalian and 

 reptilian fauna which Cautleyand Falconer were the first to bring 

 to light. In pliocene times, before the greater displacements 

 commenced, it is not unlikely that the Kashmir basin drained at 

 the north-west end into the Kishingunga Valley to Mozufferabad, 

 and that of Hundes and I.adak trended towatds the same direc- 

 tion via Dras. 



The southern boundary of this long alluvial plain was formed 

 by the present peninsula of India, and probably of the extension 

 of the Garo and Khasi Hills westward to the Kajmahal hills. '-' 

 Depression has been considerable in the neighbourhood of 

 Calcutta, 3 nearly 500 feet. We know probably only a portion 

 of the alluvial deposits. At 380 feet beds of peat were passea 

 through in boring, and the lowest beds contained fresh-water 

 shells ; the beds alio were of such a gravelly nature as to indicate 

 the neighbourhood of hills, now buried beneath the Ganges 

 alluvium. This is precisely the appearance of the country above 

 Calcutta on approaching the present valley of the Brahmaputra. 

 The western termination of the Garo Hills sinks into these later 

 alluvial deposits, and along the southern face of the range up to 

 Sylhet, the waters of the marshes, 4 during the rainy season wash 

 the nummulitic rocks like an inland sea, and point to the very 

 recent depression of all this area. The isolated granite hill-tops 

 jutting up out of the marshy country from Dhoobri to Gwalpara 

 and on to Tezpur all testify to the same continuous depression 

 here. It is exactly north of this that we find the Sivalik forma- 

 tions absent at the base of the Himalayas, and we have the 

 evidence of exclusively marine conditions in pliocene times at the 

 base of the Garo Hills. 5 We find also a large development of 

 marine beds above the nummulitic limestone in the Jaintia 

 country,'' passing up comfonnably into a great thickness of upper 

 miocene sandstones of the Burrail range. In such sandstone 

 north of the Munipur valley the only fossils I found were marine 

 forms. 



This gradual depression of the delta of the Ganges, the relative 

 higher level of the water-parting and shifting of the Punjab rivers 

 westward, appear to be only the last phase of that post-pliocene 

 disturbance which broke up the Assam Sub- 1 limalayan lacustrine 

 system draining into the Arabian Sea. Zoological evidence 

 which I cannot here find space to quote is also in favour of this 

 former connection of the now separated waters of the Ganges 

 and Indus basins, and the hill tracts of the Garo and Khasi Hills 

 with peninsular India. 



The ground where the miocene rocks are absent is not where any 

 denuding force from the north could have acted with any abnormal 

 intensity. It lies under the hills where no great tributary enters 

 the plain, and might have removed the above formation. All 

 the evidence is in favour of the axis line of depression in the 

 Ganges delta between Kajmahal and the Garo Hills extending 

 thus far, and that the miocene beds, once continuous, are here 

 thus lost to sight beneath the more recent yet extensive gravels 

 and conglomerates that here occur, aud have partaken also of a 

 last .slight elevation of the mountain chain. 



Even if we were to raise the rocks below the delta up to the 



' Elanford and Medlicott, ice. tit. p. 



- Blanford and Medlicott, Memoirs of the Geological Society 0/ India, 

 p. 31. 3 Loc. lit. p. 397. 



4 For a very excellent account see Hooker's Himalayan Journals, pp. 

 263-265. 



brooke, Geological Transactions, vol. i. p. 13s. 



6 H. H. Godwin-Austen./. A. S. B. 1860, pp 12 and 152. 



