1879.] J. T. Walker —On Indian Pendulum Observations. 255 
the geodetic latitude, computed, from Kalianpur, with the constants for 
the figure of the earth which are employed in all the geodetic calculations 
of this Survey ; the difference would be diminished by l"-4, if Colonel 
Clarke’s constants of 18GG had been employed instead. The astronomical 
azimuth at Delira is 12"’2 in defect of the geodetic azimuth, also computed 
from Kalianpur ; consequently, as the latitude is 30° 19' 57", the deflection on 
the prime vertical—being equal to the azimuthal error x the cotangent of 
the latitude—may be taken as 20"'8. The resultant of the two deflections 
is 43" ; it may be either increased or diminished by the local attraction at 
Kalianpur, which, however, is almost certainly not large. Assume tho 
total deflection to be 43" ; then the horizontal attraction which would pro¬ 
duce a deflection to that extent is equal to gravity x tangent of the de¬ 
flection = '0002 g. Now we have seen that at More the deficiency of 
vertical attraction diminishes the number of vibrations of a seconds pen¬ 
dulum by about 21 vibrations per diem ; and this deficiency of force is 
equivalent to '0005 g. Hence it appears that the variations of attrac¬ 
tion which arise from hidden causes, below the Himalayan Mountains, may 
be from two to three times as great as those which arise from the moun¬ 
tains themselves; this being the proportion of the maximum vertical 
deficiency which has yet been met with, to the maximum horizontal attrac¬ 
tion which has yet been met with. 
Thus the Pendulum Observations in India have furnished much evi¬ 
dence in confirmation of the accuracy of the Geodetic Operations in India, 
tending to show that the latter have not been influenced, either by the 
positive attraction of the Himalayas, or by the negative attraction of tho 
Ocean, to anything like the extent which each disturbing element, acting 
alone, would produce, were it not neutralised by the interior constitution of 
the subjacent matter. 
It would seem that measures of variations of gravity on the earth’s sur¬ 
face can never be made to supersede direct measures of the earth’s figure. 
Each process is supplemental to the other ; for all determinations of varia¬ 
tions of gravity, in widely separated localities, necessarily rest on an exact 
knowledge of the figure ; and a knowledge of the variations of gravity gives 
greater exactitude to the determination of the figure. Thus there is no 
necessity to divorce the two processes, and to relegate either the one or the 
other into obscurity; on the contrary, the simultaneous employment of 
both, whenever practicable, appears to be most desirable, in the general 
interests of Science. 
