( 437 ) 
small inclination fi and that electric charges exist at the front and 
at the back of the discharge. 
In that case we again find the formula (51), in which y, v 2 u x 
and u 2 are given by the formulae 
v l -^k l X . 
v t ^k 2 X' 
« 1 =V^ + *i3 r 
u a — k a *HX — k a T 
The place of (52) is taken by the formula 
.( 60 ) 
From (5J) and (60) we conclude 
U = k 2 k 2 HX .(61) 
and 
tglt = (k,-k l )H -I .(62) 
Whatever the inclination may be, we always find the right value 
for the velocity U. So it appears reasonable to suppose that this 
inclination is determined by the local conditions of the metal and 
that the electric intensity Y and the charges to which it is due, 
adjust themselves to it according to (62). 
Physics. “ The atomic volume of allotropic modifications at very 
low temperatures By Prof. Ernst Cohen and Dr. J. OlieJr. 
Communication N°. 113 from the Physical Laboratory at Leiden. 
(Communicated by Prof. H. Kamerlingh Onnes}. 
(Communicated in the Meeting of October 30, 1909). 
1- In the discussion on'a communication: “The allotropic forms 
of silver and gold”, made by one of us in the meeting of the 
eutsche Bunsengesellschaft at Dresden ') the question was raised 
whether the atomic volumes of the different allotropic modifications 
0 a certain element become equal at the absolute zero point. As 
\ e ans wer to this question, which can only be given by expe- 
ri ment, is in the closest connection with some other points 
concerning the periodic system of the elements to which we shall 
back later on, we have carried out an investigation in the 
a ove mentioned direction, which may be briefly described here.*) 
] ) Zeitschrift far Elektrochemie 21, 589 (1906). 
) The full discussion will shortly appear in the Zeitschrift fur physik. Ghemie 
