1327 
a time &, of which we suppose that the integral f gd, taken for 
different successive intervals 0, yields values which are independent 
of each other. We shall represent these values by Q,, Q, ete. If 
we further call the path passed over in 3 s,, we find on ‘integration 
over a number of r intervals: 
4 
AN 
il udt = UU; =—ps, + Q, 
feat 44 EEn = —ps, + Q 
(v--1)0 
Summation of these equations yields : 
Ht =u, =—pts+ 22. 
By taking r large, the terms of the righthand member increase inde- 
finitely, whereas the lefthand member, which consists of two terms 
only, will not increase. We can, therefore, choose v so great that 
the lefthand member may be neglected. Then, if we represent Xs, 
the quantity which we wish to determine, by A, we get: 
in 
A=—2Q 
P 
= TE 
A = ee 
Pp P P P u” 
This follows from the supposition that the quantities (} will be 
independent of each other. 
In order to get an estimation of the value of the righthand member, 
we proceed as follows : 
5 1 1: 
DP 
—_M Mr 
In this J/ denotes the mass of the suspended particle; we shall 
denote that of the molecules of the medium by m. S& is the force, 
and &, the z-component of the force which a definite molecule exerts 
on the particle. The 2-sign refers to the different molecules which 
are at the same time in interaction with the particle. If further by 
EY, 2, Uv, w we represent the coordinates and the components 
