523 



tesimal mass dy situated in a point 

 ^:=r:z^=|;^_---_-^-_-^-_-_-_-^_-_: Q F of tiic sti'ip SQ On a small mass 



(lb situated in the rib AC of the 

 prism. The distance of the strip SQ 

 from the rib ^C be a, the distance 

 — - at which the part db is situated 

 from the projection of P on AC, 

 be b. 



As the attraction of P on db is inversely proportional to the 

 square of the mutual distance and proportional to the size of the 

 part db, we may put : 



K^ 



db 



+ 6= 



We now obtain the total attraction of the part P on the whole 

 line AC by integrating this expression between the limils -|- oc 

 and — 00 



4-x _|_oo 



r db 1 b r 

 —T-r. = - % ^9 - = 



J a^ -}- b^ a a J 



JX 



The attraction of each part of the strip SQ on the whole line 

 AC is consequently inversely proportional to their mutual distance. 

 This holds for e\ery other part of the strip and consequently for 

 the entire strip SQ, and for every other strip running parallel to J C. 



We shall now calculate the attractive 

 force exercised in an axial direction 

 by a strip SQ. 



Be L a point of the strip SQ, M a 

 point situated in the rib, whilst we 

 ,M suppose that both L and J/ are situated 

 in a plane, normal to the rib. We 

 found that the attractive force of the 

 strip running through L on the line 

 situated in the rib M, is inversely 

 proportional tc their distance LM = c, 

 consequently 



Fig. 2. 



c 



If the distance from L to the line TM be 

 ponent is 



Proceedings Royal Acad. Amsleidam. Vol. X.VI. 



;•, the axial coni- 

 34 



