0838 
Physics. — “On the Hain. effect, and on the change in resistance in 
a magnetic field at low temperatures. VII. The Haut. effect for 
gold-silver alloys at temperatures down to the melting point of 
hydrogen”. By Brner Beckman. Communication No. 132c¢ from 
the Physical Laboratory at Leiden. (Communicated by Prof. 
H. KAMERLINGH ONNES). 
(Communicated in the meeting of December 28, 1912). 
This communication is a continuation of Comm. N°. 130%. 
IV. Gold-silver alloys. 
$ 10. Measurements at temperatures of 290° K., 20°.3 K. and 
14°.5 K. of the Harr effect for three Au-Ag alloys (I, II, III) con- 
taining a large percentage of gold were published by KAMERLINGH 
Onnes and myself in Comm. N°. 129a, § 12, and in Comm. N°. 130c, 
§ 16. The results of my measurements made-on one (1) of these 
alloys at 90° K. were given in $ 9 of Comm. N°. 1305. I have since 
investigated three other alloys containing a greater percentage of 
silver, and in the present paper the results of these new measure- 
ments on the Harr effect for Au-Ag alloys are given and are dis- 
cussed in connection with the former results. 
The observational method was the same as was formerly used, 
viz. the form of the compensation method developed by L&sReEt *) 
as used by vaN EvERDINGEN *). An iron-clad THomson galvanometer 
was used, with a period of about 4 sees, and a sensitivity of about 
1 mm. deflection at 2.5 m. distance for 5 & 10-8 volts. In this 
method disturbances produced by the thermo-currents arising from: 
the thermo-magnetic effect of von ErtinGsHAvsEN are completely 
eliminated only in the case of instantaneous closing of the main 
current circuit. On account of the comparatively large period of the 
galvanometer this was not possible in the present experiments; but 
still, these disturbances were too small in the present case to be 
observed. 
The main current was 0.5 to 1 amp. The plates were circular 
(11 mm. diam.) with point electrodes. The resistance of the plates 
was measured as well as the Harr effect. 
The alloys were obtained by fusing pure gold and silver in a 
porcelain crucible, and then rolling them out. They were all sub- 
mitted to analysis. I am greatly indebted for these analyses to 
1) Lepret, Diss. Leiden 1895. Comm. Leiden NO, 19, 1895. 
2) IX. vAN EverDINGEN, Comm. Leiden. Suppl. N°. 2, Cf. also H. KAMERLINGH 
Onnes and B. BECKMAN, Comm. N°. 129a, 1912. 
