Figure 62. Breguet-Saxton metallic thermometer first invented about 1817 by the
instrument maker Louis Abraham Breguet. The first of this type was composed of
platinum, silver, and gold with the silver placed in the center. Differential
expansion of the metals provided the temperature measurement. In 1848, Joseph
Saxton made a similar one for the U. S. Coast Survey but it was inaccurate.