Knowing the cross section in millimeters, Q, of the bar, and observing
the temperature, t, in degrees Centigrade, its conductivity, x, as
compared with mercury can be determined. If L be the distance, h l or k
i, in meters, then
x = (1/m) (L/Q) (1 + at).
For pure metals the value of a may be taken at 0.004; but alloys have a
different coefficient. The instrument is made by Siemens and Halske,
and is accompanied by a table giving resistances per millimeter of the
measuring wire, N.--_Zeitsch. für Elektrotechnik_.
* * * * *