You probably have
forgotten that when two half-rings of dissimilar metals are joined
together and one is suddenly heated or chilled, there is produced
at the opposite connecting point a feeble current which will flow
until the junctures are both at the same temperature. You might
call this a thermo-electric thermometer, or a telethermometer, or
a microthermometer, or any of a dozen names."
"Yes," I agreed mechanically, only vaguely guessing at what he had
in mind.
"The accurate measurement of temperature is still a problem of
considerable difficulty," he resumed, adjusting the thermometer.
"A heated mass can impart vibratory motion to the ether which
fills space, and the wave-motions of ether are able to reproduce
in other bodies motions similar to those by which they are caused.
At this end of the line I merely measure the electromotive force
developed by the difference in temperature of two similar thermo-
electric junctions, opposed. We call those junctions in a
thermopile 'couples,' and by getting the recording instruments
sensitive enough, we can measure one one-thousandth of a degree.
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