"Let us prepare a thermometer," said Barbicane.
We may imagine that an ordinary thermometer would afford no result under the circumstances in which this instrument was to be exposed. The mercury would have been frozen in its ball, as below 42@ Fahrenheit below zero it is no longer liquid.But Barbicane had furnished himself with a spirit thermometer on Wafferdin's system, which gives the minima of excessively low temperatures.
Before beginning the experiment, this instrument was compared with an ordinary one, and then Barbicane prepared to use it.