1386 
deviations do not exceed 4°/,, which corresponds to a difference 
of 0.004 ohms at the most. 
The last measurements may also serve to control whether the 
results of the earlier ones were not fully accurate owing to the 
contact resistances. The deviations that I have just mentioned might 
arise from this source of error, but, as they go in different directions 
at ¢—=—78°.6C. and ¢=-—-193°C. one is inclined to think that 
these deviations may originate in other errors too, for instance in 
variations of the temperature bath at t= —78°.6 C. (solid carbonic 
acid and ether). 
QO. ReicHennem') and J. KOENIGSBERGER*) have examined pyrite 
from Val Giuf, Graubiinden and have found a minimum of resistance 
at about ¢=—10° C. This pyrite has a specific resistance of 
0.0240 at O°C., thus eight times larger than mine. An explanation 
of this difference of the conductivity is given by J. KOENIGSBERGER *). 
My pyrite shows no minimum of resistance above —258° C. The 
resistance throughout the whole temperature interval follows the 
formula (1), which is the same, mathematically, as 
de 
— = const. 
W dt 
It seems very probable that there does not exist any minimum 
below — 258° C., but that the resistance at still lower temperatures 
approaches asymptotically to a limit value, as is the case in, for instance, 
not perfectly pure gold and platinum. 
A. WesreLy®) has recently examined a pyrite erystal from the same 
place af origin, Malmberget, Gellivare. He found a still smaller spec. 
resistance, w, — 0.00247 and a temperature coefficient at 0° C. of 
0.00228. 
Physics. — “Investigation of the viscosity of gases at low tempera- 
tures. 1. Hydrogen.” By H. Kameruincn Onnes, U. DORSMAN 
and Sopnus Weger. Communication N°. 184a from the Physical 
Laboratory at Leiden by H. KAMERLINGH ONNES. 
§ 1. Zntroduction.*) The investigation of the dependence of the 
viscosity of gases upon the temperature at densities near the normal, 
1) O. ReICHENHEIM, Inaug. Dissert. Freiburg 1906. 
2) J. KOENIGSBERGER, Jahrbuch der Rad. u. Elektr. 4, p. 169, 1907. 
5) J. KOENIGSBERGER, Phys. Zeitschr. 13, p. 282, 1912. 
4) A. WeseLy, Phys. Zeitschr. 14, p. 78, 1913. 
5) This Comm. includes the paper on the same subject by KAMERLINGH ONNEs 
and DorsMAN, which is referred to in Comm. Suppl. No. 25. (Sept. 1912) § 6, note 1, 
