TRANSACTIONS OF THE SECTIONS. 315 



rivers, that is, irrigation canals in India and elsewhere, and on the present occasion he 

 proposed confiuinghis attention to the rivers of Northern India, with suggestions 

 as to how thev should be bridged. 



To do so, however, probably it wiU be best to give a general desciiption of the 

 plains of Northern India without attempting to infringe on the work of the geolo- 

 gist, but simply to state what is now to be fomid, and what changes in nature have 

 lately taken place and are at present being worked out. 



The plains of Northern India may be considered imder two great divisions, 

 namely, the Gangetic "\'alley and the'Valley of the Indus. Approximately it may 

 be said that from the head of the Bay of Bengal to where the Ganges escapes 

 from the hills is a little short of 1200 mUes. The general shape of the surface of 

 the country would in section be the quadrant of a very flat ellipse, with a small 

 portion of botli ends cut off* ; the total fall, rather less than lOUO feet, commen- 

 cing with rapid slopes near the hills, and ending with a fall of only one or two 

 inches in the mile at the sea. These plains consist of alluvial deposits to unknown 

 depths in alternate strata of clay and sand ; but in addition to this are to be found 

 extensive beds of limestone, known in India by the name of " kunkur." 



As a general rule, the uppermost stratum is a rich light clay from 5 to 10 feet 

 in depth, with sand below it, and it is chiefly owing to this that Upper Lidia is .so 

 very productive. Strata of clay, sand, and " kunkur " are met with at various 

 depths, and of various thicknesses, and all have a general parallelism to the sur- 

 face, but how or when deposited the author Avill not attempt to discuss. 



These plains are cut up by deep troughs or valleys, usually from 5 to 10 miles 

 broad, of various depths, from that of 10 to even 100 feet. A section of one of 

 them was before the Section ; it is through these vallej'S that the large rivers 

 wLieh are fed by the melting of the snow now meander. 



These valleys are known in India by the name of " Khadirs," aud_ as there is 

 nothing similar to them that the author is aware of in England, it will be best to 

 adhere to this local name in contradistinction to what is called Bhaugir, or the 

 high-level plain already referred to. The formation of these " Khadirs" i.a, how- 

 ever, a matter of interest to the engineer, so the author will state his views as to 

 how they were scooped out and are now being filled up. 



In the' great valley of the Dehra Doon, lying between the Ganges and the Jumna, 

 and beyond the Scwalic range, where the ground chiefly consists of boulders and 

 sand, -\\'ith a co^•ering of A-egetable soil, there are evident marks to show that these 

 two rivers stood at much higher levels than at the present day. It is also -(-ery 

 evident that the sea extended several hundred miles further inland than the present 

 head of the Bay of Bengal, so that at no veiy distant period, speaking of time _ in 

 a geological sense, the chief rivers of N orthern India must have had, when escaping 

 from the hills, their beds higher than at present, and their channels shorter; so, with 

 slopes more rapid, the transporting power of these rivers must have been much 

 greater than now, and a violent cutting back on the bed has taken place from 

 the sea, scooping out these deep troughs to excessive depths through the alluvial 

 plains. 



This also would further add to the declivity of the beds of these rivers near the 

 foot of the hills, and thus boulders could be transported for many miles further 

 into the plains than they are at present. 



It is thus the author would account for sand only being foimd to great depths in 

 the valleys of the large rivers some distance down their coiu'se, as, for example, on 

 the Beas", where the Uelhi Railway crosses it ; also near the foot of the hiUs, shingle 

 and boulders some twenty miles down the course of these rivers are to be found a 

 few feet below the sand, as in the case of the Dadoopoor dam at the head of the 

 Jumna Canal, where the foundations rest on shingle at a depth of about 10 feet 

 below the bed. 



With sand overhdng boulders and shingle it can only be supposed that the beds 

 of the rivers are here being raised, and as the Delta is extending year by year out 

 into the Bay of Bengal, the river here also is becoming higher, so it is natural to 

 suppose that all along the course of the river between these points a similar process 

 is o-oing on. This is a very important point to know ; for though this silting up may 

 * Possibly this curve may be parabolic. 



