as are terminated by Planes , &c. 267 
put -dL- = c\ and the last term becomes — fx' arc (tang. 
=£=) = + rc f j — p 5 == - T - I _ r , 
1 ... -Z I " m 7 f A/ /* ? I r 1 2 1 ✓ „ . „ 2 . 1 ..lit V' r 2, _L v /2, f • ** 
therefore 
If the fluent is to begin when x' = 0, the correction is 
I have dwelt the longer on this proposition, because the at- 
traction of right prisms, in all cases, may be made to depend 
on it. 
Cor. 1. It is in the first place evident, that b}^ means of this 
proposition, we may find, by parts, the force, both in quantity 
and direction, with which a point q, any where on the edge 
pm of the scalene prism represented by fig. 9, is attracted. 
The same may be said of the action on p' any where in the 
produced axis ; this will be the difference of the actions of two 
prisms, like that in the figure. 
Cor. 2. Moreover, if, instead of the prism in fig. 9, the point 
q was placed any where on the edge of a prism whose base is 
the triangle quv, fig. 10, the action may still be found ; for it 
will now depend on the difference of the action of such prisms 
as were treated of in the Proposition ; that is to say, the action 
of the prism whose base is quv as the difference of the actions 
of those whose bases are qvr, qur, qr being a perpendicular 
on vu produced. 
— rc L . c —j— x L “. 
