90 
ARCHDEACON PRATT ON THE ATTRACTION OF THE 
any manner whatever, so long as its height is always small and the same at the same 
distance from the axis of y. 
The property, then, in its most general form is this. If a mass lie on the space 
QR/-^, always of small comparative altitude and having its section perpendicular to 
the axis of y always the same (so far as it falls within the curve), the section itself 
being of any conceivable form whatever, then the attraction of the mass nn A is pre- 
cisely the same as if it were concentrated in the point a (I should mention that in 
drawing the figure I have for convenience made the dimensions in y one-third of the 
size they should be compared to those of x). 
51. In the previous articles we have seen that by far the largest part of the attrac- 
tion, at the three stations, arises from the elevated regions lying parallel to the line 
QR in figs. 4 and 5, running from west-north-west to east-south-east. If, then, 
we take A in the figure of last article to be Kaliana, and Ax in the north-north- 
east direction, we may make the parts of QRrg- nearest A coincide as nearly as pos- 
sible with the attracting mass of the Himalayas and the regions beyond, by giving 
the vertical section MN the right form : and the parts of this mass towards the 
extremities, and therefore furthest from A, will have a less and less eflfect in the direc- 
tion Ax, both on account of their increasing distance and the larger angle at which 
they act with Ax. Hence we can easily conceive that such a form can be given to 
the transverse section MN as to make the mass on QRrq in its effect in the direction 
Ax a very fair representative of the actual mass, producing the deflection of tlie 
plumb-line at Kaliana. This being the case, the property I have demonsti-ated, 
together with the result arrived at in art. 49, shows that Aa, or a in the equation to 
the curve, =1688 miles. 
52. By taking different values for a in the curve we may find curves differing in 
their dimensions, but possessing the same property. 
Fig. 7. 
In the accompanying figure (fig. 7) three such curves are drawn having a common 
