74 
ARCHDEACON PRATT ON THE ATTRACTION OF THE 
great elevations in these parts are the Hindoo Koosh and the Caucasus ; but these 
are of so small an extent and width, that when levelled down they will not sensibly 
raise the averag'e height of the large compartments in which they stand. In Arabia 
I believe there are some moderately elevated table-lands. But their effect will be 
somewhat lessened by the intervening ocean, as its density is only two-fifths that of 
rock. Moreover the effect will be sensible, if sensible at all, only in the direction of 
the prime-vertical at the three stations, and not in the meridian, which is the only 
direction of importance to our calculation. The effect is also in part counterbalanced 
by those parts of the countries of Burmah, Malacca, Siam, and China, which lie out- 
side the Enclosed Space, and are on the opposite side of the Indian Arc from Arabia. 
The effect of the Ghat Mountains on the west of India, and the table-land of Central 
and Southern India, will be counteracted in part by the extensive ocean beyond them. 
Their effect upon the northern Station A. will be inconsiderable ; and with regard to 
B. and C., what effect they may have will be chiefly in the prime-vertical. So to the 
east of the Enclosed Space. The parts of China beyond it, in which there is only a 
mountain range on the sea-coast and of no considerable elevation or extent, will 
have but a feeble influence. Hence these regions around the Enclosed Space may be 
left out of the account. And those lying still further off and running to the anti- 
podes may also be passed over, as the distance of their several parts is so great com- 
pared with the distances of A, B, and C from each other, that the resultant attrac- 
tion of those regions, whatever high table-lands may occur in them, must be almost 
precisely the same at all three of the stations. It would not be difficult indeed to 
show that this resultant attraction is itself of imperceptible amount. 
We may fairly conclude, then, that the disturbing cause lies wholly in the enor- 
mous mass included within the Enclosed Space, which I shall now describe. 
35. The Himalayas rise abruptly from the plains of India to 4000 feet and more, 
and cover an extensively broken surface some 100 or 200 miles wide, rising to great 
heights, — perhaps 200 summits exceeding 18,000 feet, and the greatest reaching more 
than 28,000. The general base on which these peaks rest rises gradually to 9000 or 
10,000 feet, where it abuts on the great plateau north of the range. The character 
of the country to the south of this plateau is much better known than that to the 
north. If a circle be drawn around A with a radius =5°‘046 (the value of a^^), it will 
pass over the highest part of this plateau, just taking in Leh or Ladak within its 
compass. The general features of the country within this circle may be learnt from 
the Survey and other maps of India. This portion, then, of the Enclosed Space I shall 
call the Known Region, and the whole that lies beyond it the Doubtful Region. By 
introducing an arbitrary factor into the calculations I shall be able to separate the 
effects of these two divisions, and to gather what influence our uncertainty in the 
Doubtful Region has upon the total result. 
36. These two divisions join on the great plateau. On this plateau are H’Lassa^ 
according to Humboldt 9590 feet above the sea; Gertrope, 10,500; and Leh or 
