2 3% Of the SOLIDS 



Then, if we find <p fuch that fin <p = |£ x BC ^ ^^ 



tion of the redangle CL is n . <p, n denoting the thicknefs of the 

 plate. 



c \r -c r , BL BN , 



So alfo, if fin ?' = — x ^, the attradion of LN is =; 



s . <p'. 



If fin <p # = -^- X -^p, the attradion of NL' is =. n . <p\ 



T>T ' •Dp 



Lastly, If fin f'" — — > X -^, the attraction of L'C r: 



Thus the whole effect of the plane MD', or / — 

 n (<p + p' + P" + 9"). 



We may either fuppofe p, q> &c. defined as above, or by the 

 following equations, where >?, j?', ?/', &c. denote the angles fub- 

 tended by the fides of the re&angles that meet in B, beginning 

 with BC, and going round by L, N and L' to C. 



fin 9 — fin n . fin */ 

 fin <p' — fin t)' . fin n ' 

 fin ** == fin „* . fin ,'" 

 fin <p"' — fin »/" . fin ^ 



If the computation is to be made by the natural fines, it will 

 be better to ufe the following formulae : 



fin <p — - cof ( n — n ) — - cof (>? + n ) 



fin<p' =Icof(^ — „') — 3cof(>' + „') 

 3 * 2 



finp* 



