981 
: é b, 
the form given here the rv ordinates are only —*- times smaller. But 
) lim 
the advantage of the form given here is obvious, when there are 
different kinds of substances from the point of view of the law of 
correspondence. First of all it points out the cause for the existence 
of these different kinds, about which cause the form given originally 
does not reveal anything. Secondly it appears that attempts to find 
perfect correspondence between these different kinds must fail, and 
have certainly no chance of success by variations in the a and m 
ordinates. And thirdly it shows that the deviation between the 
different kinds of substances is a gradual one, and the eoincidence 
in the rarefed gas-state is restored. 
Physics. — “On the Harr-efject, and on the change in resistance in 
a magnetic field at low temperatures. V1. The Harrefject 
for nickel, and the magnetic change in the resistance of nickel, 
mercury and iron at low temperatures down to the melting 
point of hydrogen”. By H. Kameriincu Onnes and Berner 
BECKMAN. Communication N°. 182a from the Physical Laboratory 
at Leiden. (Communicated by Prof. H. KAMERLINGH ONNES). 
(Communicated in the meeting of November 30, 1912). 
$ 17.) Magnetic change in the resistance of solid mercury. The 
resistance was measured of mercury contained in a glass capillary 
9 ems. long, and of 0.12 mm. diameter. The capillary was U-shaped, 
and to either end were fused two glass leading tubes which were filled 
with mercury. The resistances were measured by the KonLrauscu 
method of -overlapping shunts, in which the main current was 
J = 0.006 amp. The mercury was frozen by blowing cooled hydrogen 
vapour into the cryostat through a glass tube whose lower extremity 
reached below the resistance. The resistance was found to be 
Go a at PS Be Treo he 
0,1014 T=- 20°,3 
0,0618 Fl 
1) The sections of this paper are numbered in continuation of those of Comm. 
N°, 130c (Oct. 26, 1912). 
| 64 
Proceedings Royal Acad. Amsterdam. Vol. XV, 
