947 
Physics. — “On the change induced by pressure in electrical resis- 
tance at low temperature.” 1. Lead. By H. KAMERLINGH ONNES 
and Benet BECKMAN. Communication N°. 132° from the Phy- 
sical Laboratory at Leiden. (Communicated by Prof. H. Kamer- 
LINGH ONNEs). 
(Communicated in the meeting of November 30, 1912.) 
§ 1. Introduction. The difficulties which encompass the explanation 
of the variation of resistance with temperature on the lines of the 
theory of electrons as developed by RircKe, Drupr and Lorentz, and 
which are of particular import within the region of low temperatures, 
render it desirable to undertake an investigation of the behaviour of 
resistance at these temperatures under modification of various external 
conditions. With that end in view we have already developed in 
certain directions an investigation of the behaviour of resistance in 
a magnetic field (and of the closely allied Hat phenomenon). In 
the present paper we communicate the result of a first investigation 
of the change of resistance under the influence of uniform hydrosta- 
tical pressure. Our first aim had been to trace the connection between 
pressure coefficient and temperature coefficient. Our data, however, 
are as yet too few to serve as a basis for deductions — however 
obvious these may be — affording an explanation by means of 
vibrators, electrons, dissociation or variation of the mean speed ’). 
The dependence of specific resistance (w,,) upon pressure (p) can, 
in general, be represented by the formula *) 
5 
Wsp == Wisp @ bp? , 
in which a.and 6 are constants, and wi, is the specific resistance 
for p = 1. When p is not very great, this gives 
1 
WE w, (1 - ap) (: == Ta ap) = uy (1 + YP) 
for the resistance of a wire which is subjected to uniform hydro- 
statical pressure, in which 
1 
=d a B 
and 8 is the compressibility. Hence the variation 4w = w— w,, 1s 
given by 
Aw 
w 
In the following only y has been measured. 
=p 
1) B. Beckman, Upsala Univ. Arsskrift 1911, p. 107. 
*) B. BECKMAN, l.c. p. 16. 
