1430 
when it was found that the resistance of tin disappeared suddenly 
too, we succeeded in making a less doubtful experiment than is 
possible with mercury, with a flattened out constantan wire, which 
was covered with a thin layer of tin’). The resistance of the layer 
of tin disappeared with a weak current and at a low temperature, 
while the constantan remains an ordinary conductor at that tempe- 
rature. 
Thus we may for the present adhere to the usual laws of current 
division, and in this extreme case continue to assume that in so 
far as the appearance of the potential difference is to be explained 
by a local heating in consequence of a local change in difference 
of the chemical nature of the conductor from pure mercury this 
disturbance must extend over the whole section of the current path. 
Thus the conclusion drawn in § 9 concerning the probability of 
the existence of a micro-resistance remains valid. 
(To be continued). 
Physics. — “The radiation of Radium at the temperature of liquid 
hydrogen”. By Madame P. Curie and H. KAMERLINGE ONNes. 
Communication N°. 135 from the Physical Laboratory at 
Leiden. 
One of the most remarkable peculiarities of radio-active substances, 
is that the radiation is independent of the temperature. Neither do 
the radio-active constants change with the temperature. These two 
facts are related to each other; they prove that the radio-active 
transformations are not affected by the influence of temperature, 
which plays such an important part in the chemical transformation 
of the molecules. 
According to the theory of radio-active transformations, the 
intensity of radiation of a simple substance is proportional to the 
rapidity of the transformation, so that a change in one of these 
quantities involves a change in the other. 
The experimental investigations of the influence of temperature 
lave been concerned with the measurement of the radio-active 
constants and the intensity of radiation of certain substances. P. 
Curr: has shown that the law of transformation for the emanation 
does not change at a temperature of 450° C. nor at the temperature 
of liquid air’). Various observers have proved that the penetrating 
1) it is to be noted, however, that the current density in the thin layer had to 
be reade very weak Comp. the following part of this Communication VIII, $ 16, 
2)°P. Corte, GC. BR: 1903. 
