HIMALAYAS ON THE PLUMB-LINE IN INDIA. 
85 
43. Adding together the results of the last article, we have — 
Deflection of plumb-line in meridian at A . . . =27*853 
Deflection of plumb-line in meridian at B . . . =11*968 
Deflection of plumb-line in meridian at C . . . = 6*909 
Deflection of plumb-line in prime vertical at A= 16*942 
Deflection of plumb-line in prime vertical at B= 4*763 
Deflection of plumb-line in prime vertical at C= 2*723 
Difference of meridian deflections at A and B= 15*885 
Difference of meridian deflections at A and C = 20*944 
Difference of meridian deflections at B and C= 5*059 
The first of these quantities is considerably greater than 5"*236, the quantity brought 
to light by the Indian Survey. And the values of the deflections at B and C bear a 
far higher ratio to those at A than has been generally supposed. For even Kaliana 
was selected by Colonel Everest in the expectation that it would be beyond the 
sensible influence of mountain attraction ; whereas even at C the deflection in the 
meridian=6"*909, if the heights have been rightly assigned in this approximation. In 
the following articles I shall examine these values more minutely, and consider the 
effect of various hypotheses for reducing them. In the mean time I will write down 
the following results from these values for the deflections : — 
Total deflection at A=32*601, and in azimuth .... 31 18 East 
Total deflection at B= 12*880, and in azimuth .... 21 42 East 
Total deflection at C= 7'426, and in azimuth .... 21 31 East* 
44. In attempting to reduce the amount of deflection deduced by these calcula- 
tions, the first thought that comes to mind is, that the density of the attracting mass 
may have been chosen too large. I have made it 2*75 of distilled water, which is 
that which was assigned as the mean density of the mountain Schehallien in the cal- 
culations of Maskelyne. This can hardly be too great; for, as I shall soon show, a 
very large share of the deflection is produced by the attraction of the elevated plateau 
which lies in Thibet and south of that country; and as this is on an average 10,000 
feet or more high, the lower part of the materials must be denser rather than lighter 
than those of a mountain of inconsiderable altitude. If, however, we do reduce the 
density, say to 2*25, which is yielding much, still the deflections and their differences 
are reduced by only one-fifth part, and therefore this will not solve the difficulty. 
45. The next thought is, that 1 may have assigned too great a mass to the Doubt- 
* Some idea may be formed of the amount of these deflections from the following representation. Conceive 
three hemispherical mountains of granite to exist close to the three stations A, B, C, their bases being hori- 
zontal and just coming up to the stations, and the centres of the bases bearing respectively 31° 18', 21° 42', 
21° 31' east of the north meridian. That the horizontal attraction of these hemispherical mountains on the 
plumb-line at the three stations may be equal to the attraction of the Himalayas and the regions beyond, the 
diameters of their bases must be respectively 5, 2, miles very nearly. 
MDCCCLV. N 
