56^ 

 76) 



314 On tlie influence of Mountain- Attraction [No. 4. 



of the Indus, the nearest point of the sea. The line joining the 

 sea with the foot of the hills passes over 720 miles (or 60 stations 

 at 12 miles apart) and is about perpendicular to the axis above de- 

 scribed, which is 156 miles beyond the foot of the hills. 



Pursuing the same course as before, I find that the aggregate 

 change of level of the foot of the Kashmir Hills above the sea 

 level, owing to Mountain-Attraction not being taken into consi- 

 deration, 



43" C 156 156 156 



= 12.3 x • ] + + .- +' — 



40" (168 180 8 



43 (11 1 ) * 



= 12.3 x X134- + + +—[ 



40 ( 14 15 73 ) 



= 171.9 * 1.694 = 291.2 feet. 



These calculations, then, if correct, show that the plains at the 

 foot of the Darjeeling Hills are higher above the sea-level than the 

 Survey makes them by 189 feet : and that the plains at the foot of 

 the Kashmir Hills are higher above the sea-level than the Survey 

 makes them by 291 feet. This gives 102 feet in favour of the plains 

 near Kashmir above those near Darjeeling, arising from this cause. 



10. I have yet to take into account the effect of Mountain- 

 Attraction on the change of level along the line of stations con- 

 necting the plains with the mountains of which the altitude is 

 under consideration. The law of deflection begins to alter from 

 that of the inverse distance as soon as we enter the mass itself — 

 just, as is well known, in the case of a sphere ; a point outside it is 

 attracted with a force varying inversely as the square of the dis- 

 tance from its centre, and therefore increasing as the point ap- 

 proaches : but as soon as the point enters the sphere it is attracted 

 with a force varying directly as the distance from the centre, and 

 therefore diminishing : the attraction at the surface of the sphere 

 is greater than on any point outside or inside. 



* I may observe that I have summed this and the previous harmonic series by 

 using a table of cosines and secants, and adding up the cosines of the angles of 

 •which the secants are 14, 15, 16, &c. 



