  When He gas is injected from room temperature into boiling liquid N$_{2}$,
boiling is suppressed, leaving liquid surface flat like a mirror. Although the
qualitative explanation for this phenomenon is known [Minkoff G J \textit{et
al}. Nature 1957;180(4599):1413-4.], it has not been studied quantitatively and
comprehensively yet. In this report, we made careful simultaneous measurements
of temperature and weight variation of the liquid. The results clearly indicate
that the boiling suppression is caused by cooling of the liquid with "internal
evaporation" of N$_{2}$ into the He bubbles.
