240 PROFESSOR CLERK MAXWELL OX STRESSES IN RA RIF I ED 
If the molecules are “ rigid-elastic ” spheres of diameter s, 
B=* * * § iw*V.(17) 
If they repel each other with a force inversely as the fifth power of the distance, so 
that at a distance r the force is then 
B =(s)V.< 18 > 
where A 3 is the numerical quantity 1 '3682. In this case B is independent of V. 
The experiments of 0. E. Meyer,'"' Kundt and Warburg,! PuLUJ,t Von Ober- 
mayer,§ Eilhard Wiedemann, || and Holm an, 1i show that the viscosity of air varies 
according to a lower power of the absolute temperature than the first, probably the 
0 '77 power. If the viscosity had varied as the first power of the absolute temperature, 
B would have been independent of V. Though this is not the case, we shall assume, 
for the sake of being able to effect the integrations, that B is independent of V. 
We shall find it convenient to write for B, 
B= 
P 
3NyU 
(19) 
where p is the hydrostatic pressure, N the number of molecules in unit of volume, 
and p a new coefficient which we shall afterwards find to be the coefficient of viscosity. 
Equation (15) may now be written 
.^ 20) 
where the integrations are all between the limits — co and + go 
the form 
/=( i+mu)w* 
and f and are of 
.( 21 ) 
F (£, 77 , Q being small compared with unity. 
We may write F in the form 
F = ( 2 A ) 4 («£+/3p + y £) + + l/3-y + ly 2 £~ + /3y ?7 £+y <a ££+ *pgrj) 
+ (2A-) 1 ($a 3 f 3 + IfSp' + y 3 { 3 +£a ~fi£ 2 r) + \ccyg~ £ + l/Ey 7 /’ C 
.( 22 ) 
where each combination of the symbols «/3y is to be taken as a single independent 
symbol, and not as a product of the component symbols. 
* Pogg. Ann., 1873, Bd. 148, p. 222. 
f Pogg. Ann., 1876, Bd. 159, p. 403. 
% Wiener Sitz., 1874 and 1876. 
§ Wiener Sitz., 1875. 
|| Arch, des Sci. Phys. et Nat., 1876, t. 56, p. 273. 
American Academy of Arts and Sciences, June 14, 1876. Phil. Mag., s. 5, vol. 3, No. 16, Feb., 1877. 
