Thermal expansion of lead at low temperatures

Changes of length of a lead rod due to thermal expansion have been measured between 4.2° k and 10° k by a heterodyne-beat method in which the changes modify the capacity of a condenser in a resonant circuit. The variation with temperature of the Gfuneison constant y was deduced; the accuracy was just insufficient to show up the jump in thermal expansion coefficient at the superconducting transition.