22 Rev. 0. Fisher on Variations of Gravity and their 



hypothesis of hydrostatic equilibrium should turn out to so 

 alter the equatorial vibration-number as to make it instead 

 = +1*89, then the absolute local attraction at More would be 

 1*89 + 2'26 = 4*15, the same as that of our parallelepiped hy- 

 drostatically supported. This is merely by way of illustration, 

 because the parallelepiped only roughly represents the plateau; 

 but it shows that the hypothesis may probably be competent 

 to explain the phenomena. 



If u is larger than h + k + t, the expression, whose integral 

 is given at p. 18, may be put under the approximate form 



* 



2& + A+ * 



~a da. 



2a sec a 



But since a is in the present case but little the larger, I have 

 thought it best to calculate the attraction from the fuller 

 formula. It seems, however, that the approximate formula 

 would have given a result sufficiently exact ; for if we put a 

 successively equal to 80 and 400 miles, using the above ap- 

 proximate formula, we get the result 4*51 swings, whereas 

 the fuller formula gives 4*15. These two numbers are suffi- 

 ciently near for our purpose. 



Relying upon this, we can estimate the local vertical 

 attraction at Kaliana. 



The attraction of a cap-sector upon a point beneath it, 

 estimated downwards, is 



— pBui u + h — s/u 1 + Ji 2 — ~ J ; 

 and of its root in the same direction, 



-O- p)S*(t- </u 2 + (h + k + ty- ^u 2 + (h + k) 9 +~\ 



The condition of equilibrium gives (cr—p)t=ph. Hence the 



curvature terms cancel ; and, expanding in terms of ' , 



h + k J " ' 



-,and -, we get 



u u 



Attraction= —ph8ct\2 ^ +t \ approximately. 



Now it appears from Major George Strahan's Relief-map 

 of India that the Himalayan plateau presents a nearly straight 

 escarpment towards Kaliana, this straight face subtending an 

 angle of about 120° at that station, so that radii drawn beyond 

 this will not enter the plateau on the western, and at a long 

 distance only on the eastern side. 



