Invention Timeline - Sir John Leslie, Scottish Physicist; Inventor of the Differential Thermometer
b. April 16, 1766 and d. November 3, 1832
St. Andrew’s and Edinburgh Universities
Scottish physicist. He was the inventor of the differential thermometer, by which he was greatly aided in his researches concerning the nature of heat; he also invented the hygrometer which led to his discovery of the process of artificial freezing. He wrote “An Essay on the Nature and Propagation of Heat”; “Elements of Geometry”; and “Philosophy of Arithmetic.”
As the barometer foretells the storm
While still the skies are clear, the weather warm
So something in us, as old age draws near,
Betrays the pressure of the atmosphere.
The nimble mercury, ere we are aware,
Descends the elastic ladder of the air;
The telltale blood in artery and vein
Sinks from its higher levels in the brain;
Whatever poet, orator, or sage,
May say of it, old age is still old age.
It is the waning, not the crescent moon,
The dusk of evening, not the blaze of noon:
It is not strength, but weakness; not desire,
But its surcease; not the fierce heat of fire,
The burning and consuming element,
But that of ashes and of embers spent,
In which some living sparks we still discern,
Enough to warm, but not enought to burn.
—Henry W. Longfellow
287-212 B. C.—Archimedes discovered the principle of displacement and specific gravity.
