The Nature of Heat
Year of Discovery: 1790
What Is It? Heat comes from friction, not from some internal chemical property of each substance.
Who Discovered It? Count Rumford
Why Is This One of the 100 Greatest?
Scientists believed that heat was an invisible, weightless liquid called caloric. Things
that were hot were stuffed with caloric. Caloric flowed from hot to cold. They also believed
that fire (combustion) came from another invisible substance called phlogiston, a vital essence of combustible substances. As a substance burned, it lost phlogiston to air. The fire
ended when all phlogiston had been lost.
These erroneous beliefs kept scientists from understanding the nature of heat and of
oxidation (including combustion), and stalled much of the physical sciences. Benjamin
Thompson, who called himself Count Rumford, shattered these myths and discovered the
principle of friction. This discovery opened the door to a true understanding of the nature of
heat.
How Was It Discovered?
In 1790, 37-year-old Count Rumford was serving the King of Bavaria as a military advisor. As part of his duties he was in charge of the king’s cannon manufacturing.
Born in Massachusetts as Benjamin Thompson, Rumford had served as a British spy
during the American Revolutionary War. Then he spied on the British for the Prussians. In
1790 he fled to Bavaria and changed his name to Count Rumford.
The cannon manufacturing plant was a deafeningly noisy warehouse. On one side,
metal wheel rims and mounting brackets were hammered into shape around wooden wheels
and cannon carriages. Steam rose from hissing vats as glowing metal plates were cooled in
slimy water.
On the other side of the warehouse, great cannons were forged. Molten metal poured
into huge molds—many 12 feet long and over 4 feet across. Spinning drills scraped and
gouged out the inside of each cannon barrel.
Drill bits grew dangerously hot. Streams of water kept them from melting. Hissing
steam billowed out of the cannon barrels toward the ceiling, where it condensed and dripped
like rain onto the workers below.
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