✍ Scribed by H.C. Kramers; Tineke Van Peski-Tinbergen; J. Wiebes; F.A.W. Van Den Burg; C.J. Gorter
No coin nor oath required. For personal study only.
The propagation of heat pulses in cylindrical tubes of different dimensions filled with liquid helium is investigated at temperatures between 0.1 and 1.0°K. In the analysis of the data marked differences are noted between the temperatures above about 0.70°K and the lower temperatures. Down to about 0.70°K the observed pulses may be described as second-sound pulses broadened by irreversible processes. At the lower temperatures the mean free path of the phonons apparently becomes quite large and therefore no second sound in the proper sense occurs.
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Neclcrla~~l synopsis ?Jew measurements were made cf the specific heat of liquid helium, employing a ca.pillary-connected calorimeter and using the demagnetization method with a properly chosen paramagnetic salt for reaching temperatures below 1'K. It was found that the specific heat below 0.6"K sati
## LETTER TO THE EDITOR The specific heat of liquid helium from 1.5°K down to 0.4°K. We measured the specific heat of liquid helium under its saturated vapour pressure from 1.5 clown to 0.4°K. The temperatures below I. I°K were obtained by adiabatic demagnetization of iron ammonium alum. In this