First, a note on temperature:
The fact that Joule was born into a successful brewing business had an effect on the physicist's experiments. The in experiments on conversion of work to heat, temperature is the main factor, and thus very sensitive to error. However, Joules had extensive experience with temperature measurement from the family brewery. He used minutely accurate thermometers and a traveling microscope to etch the scale of each thermometer precisely. The well-known Manchester scientific instrument maker, JB Dancer, made these for him. Some more exact experiments where done in the cellar of the brewery in order to minimize temperature fluctuations. Research that has been done by recreating Joule's historical apparatus attests to his skill in temperature calibration and measurement.
