THE SUPPORT OF THE HIMALAYAS 105 



visible topography and its, Hayford, compensation, leaving a resi- 

 dual of 6" of northerly deflection, which is reduced to 2" if the Bessel- 

 Clarke is substituted for the Everest spheroid. Here we find a 

 very different condition from that met with in the stations further 

 east, such as Mussooree, where the Hayford lesidual is 11" greater 

 than at Murree, and the difference may reasonably be attributed 

 to the difference in geological conditions. The station of Murree 

 is situated on rocks of the lower part of the Tertiary system, as 

 developed in the Himalayas, and in the deep embayment of the 

 exposure of these rocks, which marks the junction of the Himalayan 

 system of disturbance with that of the ranges beyond the western 

 frontier. The main boundary is not of the same sharply defined 

 character as further east, but south of Murree is a broad expanse of 

 middle and upper Tertiary rocks, and the eastern extremity of the 

 Salt Range. The effect of the trough would be much smaller than 

 on the eastern sections, so far as the deflection of the plumb-line is 

 concerned, and in the absence of other stations for comparison, 

 it is impossible to discover how far the small northerly residual, actu- 

 ally found, is due to the effect of the trough, and how far to an 

 excess of the actual over the calculated attraction of the range, 

 such as was suggested by the eastern stations. In either case the 

 isolated position of the station, with none others near it for com- 

 parison, or as a check, makes it impossible to make any further use of 

 the observation, which is, at least, not inconsistent with the con- 

 clusions drawn from the stations further east. 



« 

 A list of the gravity stations in the Himalayan and Siwalik 

 regions is given in table No. 30 (page 106), arranged in groups 

 from west to east, as in the case of the latitude stations. It will 

 be convenient to begin with the eastern group, where the station 

 Sandakphu at about 26 miles in from the main boundary, gives a 

 Hayford anomaly of + "048 dyne, equivalent to the effect of the 

 attraction of about 1,500 feet of rock at the surface, or of the equi- 

 valent of about half as much again, if the effect is due to a deficiency 

 of compensation. At the other two stations we have only the 

 Bouguer anomalies, but an approximate estimate can be made of the 

 Hayford anomalies at these stations, either by applying the Hayford 

 compensation of the Imaginary Range, as given in table No. 11, or 

 by plotting the corrections to the Bouguer anomaly at Sandakphu, 

 and the two stations of Siliguri and Jalpaiguri, and drawing a curve 



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