54 OLDHAM: THE STRUCTURE OF THE HIMALAYAS, ETC. 



and loose sands, silts and clays of the Siwaliks and Gangetic trough. 

 Now the softer sandstones, such as the New Red, used foi building 

 purposes, have a density of 2' I to 2*2, and river sand or clay both 

 about 1*9, and as these types of rock represent the material of which 

 the contents of the Gangetic trough is composed, the difference 

 between its density and that of the Himalayas is about what would 

 be expected from the difference in composition and state of aggre^ 



gation. 



The effect of such a mass of lighter material, at stations outside 

 the trough, is that the attraction towards one side is not counter- 

 balanced by that towards the other, and the material rilling the 

 Gangetic trough would exercise an apparent repulsion, causing a 

 northerly deflection at stations to the north, and a southerly at 

 stations to the south, of it. Within the limits of the trough the 

 effect would depend on the position of the station and on whether, 

 and to what extent, the effect of that portion lying on one side of 

 the station exceeded that of the portion lying on the other. 



Table 14.— Deflections due to troughs, 50 miles broad, of various 

 sections ; density '8 of average rock. 





Depth uniform. 



Depth varying from 



Station. 







1 5,000 to 



to 



to 





10,000 



15,000 



10,000 



10,000 



15,000 





feet. 



feet. 



feet. 



feet. 



feet. 



— 10 























— 9 











1 — 1 











— 8 



— 1 



— 1 



— 1 



— 1 



— 1 



— 7 



— 1 



— 2 



— 2 



— 1 



— 1 



— 6 



— 2 



— 3 



— 2 



— 1 



— 2 



— 5 



_ 3 



— 4 



1 — 3 



— 2 



— 3 



— 4 



— 3 



— 5 



— 4 



— 2 



— 3 



— 3 



— 4 



— 6 



— 5 



— 3 



— 4 



— 2 



— 5 



— 8 



— 7 



— 3 



— 5 



_ 1 



— 8 



— 11 



1 —10 



— 6 



— 8 







— 19 



— 27 



— 24 



— 16 



— 21 



+ 1 



— 6 



— 9 



— 6 



— 1 



— 2 



+ 2 



— 2 



— 3 







+ 2 



• + 4 



+ 3 



+ 2 



+ 3 



+ 6 



+ 6 



+ 8 



1 



4- 4 



+ 8 



+ » 



+ 9 



+ 8 



+ io 



+ 5 



+ 19 



+ 27 



+ 21 



+ 8 



+ 11 



+ 6 



+ 8 



+ 11 



+ 9 



+ 3 



+ 5 



+ 7 



+ 5 



+ 8 



1 + 6 



+ 3 



+ 4 



+ 8 



+ 4 



+ 6 



+ 5 



+ 2 



+ 3 



+ 9 



+ 3 



+ 9 



+ 4 



+ 2 



+ 2 



+ 10 



+ 3 



+ 4 



+ 3 



+ 1 



+ 2 



[ 202 ] 



