Page "government" Paragraph 270
from
Brown Corpus
An acoustical interferometer has been constructed and used, with helium gas as the thermometric fluid, to measure temperatures near 4.2 and 2.1 Af.
Such an interferometer provides a means of absolute temperature measurement, and may be used as an alternative to the gas thermometer.
When values of temperature derived with this instrument were compared with the accepted values associated with liquid helium-4 vapor pressures, differences of about 10 and 7 millidegrees respectively were found.
This result is preliminary, and work is continuing.
Resistance thermometers.
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1.869 seconds.