( 655 ) 
try to explain by ascribing them to forces exerted by ponderable 
matter upon electrons; these forces in that explanation become of 
primary importance when the temperature sinks to that of liquid 
hydrogen, and it is ascribed to them in particular, that they make 
the current-carrying electrons in metals suffer an important diminution 
in number at very low temperatures by their being, as it were, 
frozen to the atom by the low temperature 1 J. 
It would also be possible that the motions of the electrons which 
cause magnetism while remaining constant or changing not much at 
other temperatures, begin to show considerable changes at very low 
temperatures. 
The negative result that nothing happens even at the lowest tem¬ 
peratures, which should throw doubt upon the relative smallness of 
the variability of the magnetic atom itself, is not perhaps without 
importance when regarded as a means of weighing the value of the 
above assumptions regarding the phenomena mentioned, or as means 
of separating the group of electrons which occasion magnetism from 
groups which form the prime factors of other phenomena. 
c. Vanadium, chromium, manganese. The question has often been 
asked if a gap which cannot be bridged over exists between the 
ferromagnetic metals of the iron group on the one hand and the 
paramagnetic metals of the same group on the other, or that the 
latter metals should also exhibit a very low CuRiE-point if the 
temperature were sufficiently lowered. 
Ch. Ed. Guillaume 2 ) says with reference to the Heusler alloys 
of Mn, Al, Cu and Mn, Sn, Cu which are ferromagnetic: “The reason for 
this can be found in the fact that aluminium or tin when compounded 
with manganese, a inetal from the magnetic group, raises its trans¬ 
formation temperatures, which, following an hypothesis already sug¬ 
gested by Faraday, ought to lie very low.” It can indeed be seen 
that aluminium and tin raise the melting points of various alloys 
which they form with other metals (the series Al—An, AI—Sb, 
Na—Sn) and seem to possess the general property of raising tem¬ 
peratures of transformation. 
We might, therefore, expect that vanadium, chromium, and man¬ 
ganese should at very low temperatures exhibit either the characteristics 
of ferromagnetism (magnetization not proportional to strength of field, 
x ) Gf. H. Kamerlingh Onnes, Comm. fr. the Leyden labor. Suppl. n°. 9, p. 27 
1904 and P. Lenard, H. Kamerlingh Onnes and W. E. Pauli, These Proceedings 
June 1909, Comm. fr. the Leyden Xaborat. n°. Ill, p. 3, note 2 1909. 
2 ) Ch. Ed, Guillaume. Acles de la Soc. helv, der Sc. nat. Vol. I p. 88. 1907. 
