S4 OLDHAM: THE STRUCTURE OF THE HIMALAYAS, ETC. 



deflections normal to the general course of the range, here somewhat 



north of north-west ; it is then necessary to allow for the attraction 



of the range, the figure used being the deflection calculated for 



the Imaginary Range at a similarly situated station, and by 



deducting this from the observed deflection we obtain a remainder, 



given in the last column of the table, which may be treated as the 



effect of the trough. Here we see that at the first two stations 



there is a small deflection away from the range, indicating that 



they lie a little beyond the point at which the effect of the trough 



changes from a northerly to a southerly deflection, but these two 



stations are situated at opposite extremes of the group ; at the 



more centrally situated station of Shahpur, at about the same 



distance from the main boundary, we have a deflection of 9" 



which increases to 12" at Amritsar, representing a slope of 



about 250 feet per mile of the bottom of the trough ; at the more 



distant station of Sangatpur this has dropped to 7" and at 



Khimuana to 1" from which we may conclude that both these 



stations lie outside the limits of the trough, and, consequently, 



that the alluvium forms a comparatively thin covering over the 



rocky floor. 



Turning to the gravity observations, a list of which is given 

 in table No. 25, we find a high negative anomaly at Pathankot, 

 a lesser one at Ludhiana, and small positive anomalies at the other 



Table 25 



. — Gravity Stations in the Punjab. 



Station. 



Distance from 



outer edge of 



hills. 



Bougucr anomaly. 



Equivalent 



thickness of 



alluvium. 



Pathankot 

 Ludhiana 

 Mian Mir 

 Ferozepore 

 Montgomery . 



1 



30 



90 



90 



180 



— 179 



' — 048 

 + -004 



+ -oog 



+ -003 



23,000 



8,500 



500 







500 



three. Taking the highest of these positive anomalies as the 

 zero and interpreting the difference of the others as due to the 

 lesser density of the alluvium, we obtain the thickness given in 

 the last column, where allowance has been made, in the case of 

 Pathankot, for the effect of the compensation of the range. Here 

 again we find that the stations of Mian Mir and Ferozepore, at 



L 232 ] 



