1919.] History of the Drainage of Northern India. 83 
Kalka. The whole rien of the Upper Siwaliks is, however, 
shown in the outer hills it is evident that across the Beas 
the boulder eaioniensies ‘diminish in amount. On the Sutlej 
they are perhaps 3,000 feet and across the Jumna the actual 
boulder bed is hardly more than 2,000 feet thick. On the 
Ganges at Hardwar the boulder conglomerate i is even less and 
begins to shade into the pebbly beds of the Upper Siwaliks. 
Middlemiss! has described the Upper Siwalik conglome- 
rate in the lower hills of Garhwal and Kumaun to the east 
sandstone appear to replace one another from one locality to 
another, their respective thicknesses varying inversely as one 
another. 
The boulder conglomerate is recorded by Middlemiss as 
far east as the Nepal border, but as far as one can gather it 
gaan to be considerably ttines than on the Ganges. 
allet > mentions the presence of conglomerates in the 
Siw alike series “of Sikkim, but pebbles would seem to be neither 
so large nor so abundant as they are to the west. 
When we arrive at the corresponding series exposed at 
the foot of the Bhutan hills and described by the writer,’ we 
find that, although boulder conglomerates exist, the line of 
demarcation between them and the sandstone beds which im- 
mediately underlie them is less marked, and often, all that we 
can say is that pebbles are far more abundant at the top of the 
formation than is the case lower down 
La Touche and Coggin Brown in their respective descrip- 
tions* of the Siwaliks of the Aka and the Abor hills make no 
mention of a conglomerate, from which we may conclude that 
it is absent 
J. M. Maclaren has demonstrated the absence not only of 
the conglomerate® but of the whole Siwalik series in the 
neighbourhood of Brahmakund, and generally in the hills 
which hem in the upper portion of the Brahmaputra valley. 
e in the other direction, Ze the boulder conglom- 
erate continues with undiminished strength through Jammu, 
we find that it aiddaele disappears sen - Chenab. We may 
1 C. 8. Middlemiss, Physical ig of the Sub-Himalaya betwee 
Garhwaland Kumaun. Mem. Geol. Surv., India, XXIV, 2 (1890), pp. ve 
2 F. R. Mallet, 30 geology of the er ree district and the Western 
sear y Mem. Geol. S , India, XI, 1 (187 
8 G. E. Pilgrim, Noun on the geology me a ‘portion of Bhutan. Rec. 
— Sure. India, XXXIV (1906 
#7 ..D. Ee Touche, Notes on the epology 0 of the Aka hills. Rec. Geol. 
Surv., India, XVIII (1885), p. 122. J. a Brown, A_ geological 
Reconnaissa: 
nce through the Dihong valley, being the geological results 
of the Abor expedition. Rec. Geol. Surv., anda, REI ee p- 236. 
5 J. M. Maclaren, Geology of Upper Assam. c. Geol, Surv., India, 
XXXI (1904), p. 193. 
