28 Rev. 0. Fisher on Variations of Gravity. 



ported in that manner, because we do not know how large 

 the areas may be which would show positive or negative rela- 

 tive attraction under column 5. At any rate, the mean relative 

 to Punnse being only 042 swing, the result does not seem 

 to discredit the hypothesis that there is a distribution of matter 

 not far differing from what would accord with equilibrium for 

 the region as a whole. The attractions at these peninsular 

 stations give no information about the mean thickness of the 

 crust, assumed at 25 miles, because, in the case of an infinite 

 plain, the terms involving it (k) are neglected. 



On the whole, it is apparent that the bottom of the crust is 

 here irregular, and does not locally correspond for equilibrium 

 with the surface- contour. In a basaltic region, as already 

 remarked, this would seem natural ; for there will have been 

 no compressing action tending to produce downward bulges 

 corresponding to the elevated tracts, as would be the case in 

 a mountain-chain ; so that any downward projection into the 

 magma (i. e. root) will be due simply to the local depression 

 of the crust, owing to its having become overweighted at the 

 top, while rigidity of the crust, never crushed as in a mountain- 

 chain, would extend the depression laterally and diminish it 

 vertically. It is possible that the considerable local thickenings 

 and thinnings of the crust, which appear to occur at a few places 

 in this region, may be due to faults of large throw, such as are 

 not unknown in countries where there has been much out- 

 pouring of basalts. 



The object of this paper has been (1) to summarize some of 

 the results obtained during the Indian perdulum operations, as 

 far as they bear upon the problem of the constitution of the 

 Earth's crust ; and (2) to inquire whether, in a few of the 

 instances where it seemed practicable to approach the subject 

 by way of average, the theory of hydrostatic equilibrium gives 

 a fair explanation of the phenomena. The cases that have been 

 thus examined show that the theory of hydrostatic equilibrium 

 makes, in swings of the pendulum, 



(1) Local attraction at More . . . (about) 4*15 

 Whereas relative to Punnse it is . . . . 2*26 



Difference 1*89 



(2) It makes local attraction at Kaliana (about) — 273 

 Whereas relative to Punnse it is .... — 2'28 



Difference — 0'45 



(3) It makes mean of attraction at 7 stations 



on the basalt O00 



Whereas relative to Punnaa it is . . . . - 42 



Difference —0*42 



