270 



Mr. W. Brennand. 



DlAOKAM 2. 



of coordinates ; and suppose through P the three quadrants to be 

 drawn from S, M, I, to the opposite sides, meeting them in , w, 

 respectively. Then the normal chemical action i* tZ0. do may be 

 resolved in three directions parallel to SO, MO, 10 ; and the three 

 components in these directions will be respectively ia. drfr dd sin Px, 

 ta <70 dd sin Pm, t eZ0 do sin P*. Call these respectively rf 2 U, tPV, d?W. 



We have 



nncl hence 



sin Pm = sin cos 0, sin Pt = sin sin 0, 



U = i* II <?0 dd cos 0, V = t tt I ^0 1/0 sin cos 0, 



JJ JJ 



W = t' tt I <Z0 de sin sin 0. 



27. To find tlie value of these expressions for the hemisphere havii 

 the Sun at its apex ; we have to take from IT to ?r, and from 

 to TT, which gives 



J-v To find the chemical action of the hemisphere about S resoli 

 on the horizontal plane Q,, we have 



