248 Mr. Knight on the Attraction of such Solids 
Nor has the matter any difficulty, as far as theory * only is 
concerned ; although, actually to find the attraction, of a body 
of very complicated figure, may, no doubt, be exceedingly 
laborious and troublesome : for no one, I suppose, will con- 
ceive, that it can be done in any other manner, than by a pre- 
vious partition into more simple forms, each of which must 
have its action found separately. 
Having completed this part of my subject in the three first 
sections, I next apply the formulas, given in §. 1, to find the 
attraction of certain complex bodies, which, though not bounded 
by planes, have yet a natural connexion with the preceding 
part of the paper. Finally, the fifth section treats, pretty fully, 
of solids of greatest attraction, under various circumstances ; 
and I do not know, that any one of the problems there given 
has been before considered by mathematicians ; whilst, on the 
other hand, the results of former writers are easily derived 
as corollaries. 
For the sake of perspicuity, I have divided the paper into 
propositions, and shall terminate this short introduction by 
expressing a hope, that I may not be chargeable with unne- 
cessary prolixity. 
§• 5 - 
Of the Attraction of Planes bounded by right Lines, 
As all such figures may be divided into triangles, it seems 
natural to begin with these. 
* It is usual, I think, with mathematicians, to consider a thing as done, when it 
can be pointed out how it may be done. Thus M. Lagrange, in his excellent work 
“ De la Resolution des Equations nume'riques ,” says (p. 43) “ cette methode ne laisse, 
“ ce me semble, rien a desirer where, of course, he can only mean, as far as relates 
to theory. 
