( 322 ) 
EV FINE Ne 
e—2er y* — „2 
TL 
= a5 0 
In the same way we find for L: 
er ay Hak OR ed 
=- fer 3 PI — | Mar coe 7 (« 7) + Ms sin 7 (t zi 
2 1 An r\] 
ot |My cos (4 — De) + Myosin T (5) . 
or by approximation: 
22 An ('e—er y 2a r\) 
LS — z === —<). 22 a(t >) 
T TV | j Ate 1 i 2 ie + Ms sin 7 7 
On fs 4 Haf 
| Mun coe (ty) + Mya sin (ty) 
and for the modulus of the corresponding chance: 
i. (ae 21 5 eter y® + 22 
dese td lee 
The reasoning, according to which these formulae have been 
derived, is correct only when we may choose volume elements, which 
contain many molecules and which are yet small compared with a 
wave-length and with 7. It does not hold for the immediate sur- 
roundings of a point. Yet the not approximated formulae for [A] 
and [Zj] hold also for the immediate surroundings, provided we 
neglect the volume of the molecules. If we imagine an element 
de dy dz or dr at the distance r from the point P, then the proba- 
bility that we should find a molecule in it, is x dr. The chance, 
that we should find a molecule in it with az lying between oz and 
aa + dan, is FP, (am) dan n dt. 
If we imagine a region Az Ay Az, which contains many (p) ele- 
ments dr and which is yet small compared with the wave-length 
and 7, then the chance, that this region has a moment [ 441 ] is 
the sum of the chances of the different ways, in which that moment 
