50 PROFESSOR KELLAND, ON MOLECULAR EQUILIBRIUM. 



Let p be the distance of an element from the centre of the particle 

 B, and retain the remaining notation of the last problem, then will be 

 the volume of an elementary annulus 



= 2irp 2 dp d6 sin 9, 

 and the mass attracting this, is 



I 3 ' 



consequently the resolved part of the attraction in the required direc- 

 tion, 



-M£ „ . , ,„ • „ n PA.er« r 



y 



rrMo 3 



= ffjr^-- 2 *P 2 d P de sin OcosO 



2ttAMP rr P *e-<" . 

 = j s / / ' sin 9 cos 9 dO dp. 



Now r"- = « 2 + p - 2ap cos 9 ; 



.•. rdr = ap sin 9 d9, 



and the attraction 



ZirAMP 



a I 3 



ffe- ar p* cos dr dp 



= 75 J J e ~ P a — dr d P 



al 3 JJ ' Zap r 



= - g , f ffe— r P (« 2 + P ~ f) dr d P 

 ttAMP 



at a \a a a I 



the limits being r = a + p, and r = a — p 



ttAMP r , la* + p 2 . , la-p 1a-p 8\ , A 

 a V a a 2 a 3 / J 



