1384 
Physics. — “Measurements on resistance of a pyrite at low tempe- 
ratures, down to the melting point of hydrogen.” By Bxner 
BrckMAN. Jommunication N°. 132g from the Physical Labo- 
ratory at Leiden. (Communicated by Prof. H. KAMERLINGH 
ONNES). 
(Communicated in the Meeting of February 22, 1913). 
In an earlier publication’) I examined resistance as a function of 
temperature in the case of a pyrite crystal from Gellivare, Malm- 
berget, Sweden. Those measurements embraced the temperature 
interval + 100° C. to — 193° C. The resistance was well represented 
by the formula 
We Wot.) sn SS ee 
where W, is the resistance at O° C. and ¢ the temperature on the 
centrigrade scale. The spec. resistance at 0° C. in ohms per cube 
of 1 cm. was w, = 0,00294; a was 3.53 XxX 10-3. 
The measurements were made with a Wueatstone bridge. The 
ends of the crystal were galvanized with copper; as electrodes 
amalgamated copper plates were used. The resistance at 0° C. was 
0.101 ohms. To determine the magnitude and the variation of the 
contact resistances and of the connections with the temperature, a 
little copper prism of the same dimensions as the crystai was placed 
between the electrodes and short-circuited, and the resistance of the 
short-circuited erystal support and the connections were measured at 
the various temperatures. 
I have now had an opportunity of continuing these measurements 
on a pyrite through a larger temperature interval (down to — 258° C.). 
This last investigation was made in the cryogenic laboratory of the 
University of Leiden, and for the opportunity I owe the director of 
the laboratory, Prof. H. Kameriincu ONNes, great thanks. 
To obtain these measurements [ have used another method, which 
eliminates the possible errors of the contact resistances. The crystal 
was pressed between two copper electrodes, through which the 
current was conveyed to it. Two other electrodes were firmly 
pressed against the longest side of the crystal. The voltage between 
these was measured with the compensation apparatus *). 
In Table I the results of the measurements in Upsala 1910 are 
1) Benet BECKMAN: Uppsala Univ. Arsskrift 1911. Mat. o. naturvetenskap 1, p. 28. 
2) See H, DiessecHorst, Zeitschrift f. Instrumentenkunde 26, p. 182, (1906), 
where Fig. 2 gives a survey of the mounting. 
