312 On the influence of Mountain- Attraction [No. 4. 



Hence Mountain-attraction, if not corrected in the calculation, 

 will have the effect of making b less high above a than it really is, 

 by a space s= ac % arc v". 



5. The same will be the case where the next station (as e) is 

 lower, instead of higher, than the station from which the observa- 

 tion is made (as d). The Survey makes the distance of e below d=: 

 ef, whereas it really is ef. Hence the effect of Mountain- Attrac- 

 tion is, as before, to make the successive heights above the sea-level 

 too small. 



6. I will now endeavour to approximate to the aggregate effect 

 of this disturbing cause upon the heights of Mount Everest in the 

 East and of the newly discovered Mountain in the West. 



In communications to the Royal Society (see Phil. Trans. 1855 

 and 1859) I have shown that if through a point in the meridian of 

 Cape Comorin and in latitude 33° a straight line be drawn in a 

 direction E. S. E., that line may be regarded as an Axis of the 

 Himalayas ; such that the Mountain-Mass attracts places in the 

 plains with a force varying inversely as the distance from that axis, 

 at any rate for stations lying between the foot of the hills and a 

 distance of about 1000 miles from the axis. 



Also it is shown that at a distance of 222 miles from this axis 

 the deflection of the plumb-line towards the north is 28", and there- 

 fore in a direction at right angles to the axis = 28" sec. 22° 30' = 

 30". A line about parallel with the axis at a distance of 156 miles 

 marks the average commencement of the plains. From this line, 

 then, the law of the inverse distance according to which the deflec- 

 tions vary, may be supposed to begin. Within this limit, that is, 

 within the hill-region, the law will be different. At the line itself, 

 that is, at the foot of the hills, the deflection northwards will be = 



222 222 



28"=40", and the deflection towards the axis == 30"=43". 



156 156 



7. Assuming that these data hold good for the foot of the hills 

 below Darjeeling and for those below Kashmir, I proceed to find 

 the accumulated effect of the errors in height at a series of stations, 

 connecting the nearest point of the sea, viz. the Sandheads due 

 South, with the foot of the Darjeeling Hills, running over a space 

 of about 360 miles : and then the same at a series of stations, con- 



