Leslie's Differential Thermometer

Pristine late 19th century Leslie's Differential Thermometer. Italian made, unsigned. Excellent condition, complete original. Originally invented by John Leslie in the early 1800's; Differential Thermometers are used to measure variations in temperature. This instrument works by adding a colored liquid, such as Sulphuric acid to the 'wet bulb' (unnumbered side of U). Once the temperature rises, the pressure in the tube will push the liquid to the 'dry bulb' (numbered side), allowing for a visible measurement to be taken. This highly sensitive instrument was often used in photometry and hygroscopy, detecting even the slightest temperature variation between 2 points. Circa 1870-1899.

Similar Model Featured at Harvard University. 

Similar Model Featured in The G. Pusceddu Natural History Museum (Sardinia). 

Similar Model Featured in The Vittorio Alfieri Institute. 

Dimensions: 3.75" x 2.75" x 16.50"

Weight: 13.5 oz.