PROPERTIES OF MATTER IX THE GASEOUS STATE. 
781 
\C + K— 10 + 20 — U'+ 1C — VJ + ■?/! — 
2? + V+ V— V — 2> + v + V— V — 
M+ 24 + 24? + 24? + 24? — U— W— U— 
S(Q), S(Q). 2(Q), 2(Q), 2(Q), S(Q), S(Q), 2(Q) 
we have respectively, 
2(Q), 2(Q), 2(Q), 2(Q), 2(Q), 2(h). 2(h), 2(Q). 
And in order still further to simplify the notation, instead of 
c(Q)> o-(Q), o-(Q), o-(Q), o-(Q), o-(Q), cr(Q), o-(Q) 
we may write respectively the simple letters 
A, B, C, D, E, F, G, H. 
68. The method of considering the value of Q carried across a plane by groups 
of molecules distinguished by the directions in which they are moving, constitutes the 
essential means by which the results of this investigation are arrived at. And as it 
does not appear that this method has been resorted to by any previous writer, it 
appears necessary for me to describe at some length the preliminary steps. 
The rate at which Q is carried across a plane. 
69. Since the aggregate value of Q carried across any plane by the entire group of 
molecules must be equal to the sum of the values of Q carried across by all the various 
groups into which the gas may be divided, we have 
o-(Q) = A+B + C+L)+E+F+G+H.(1) 
cr(Q)=A+B+C+D.(2) 
<r(Q)=E+F+G+H.(3) 
<r(Q) = A-J-B+E + F.(4) 
a(Q)=C+D+H+G.(5) 
24 ? + 
ct (Q)=A+C + E+G.(6) 
24? — 
cr(Q) = B+D + F+H.(7) 
