Ward's Book of Days.

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On this day in history in 1810, died Henry Cavendish.

Cavendish was a physicist and chemist who conducted experiments on various topics such as the composition of air, water and hydrogen, the nature of heat and the properties of electricity. He calculated the weight of the earth by a method known as the ‘Cavendish Experiment’. 

Cavendish was descended from aristocratic families. His grandfathers were the Duke of Devonshire and Duke of Kent. Cavendish attended Peterhouse, Cambridge and then lived in modest circumstances in London conducting scientific experiments. When aged 40, he inherited a fortune, making him the richest scientist of his time. The French scientist Biot called him ‘the richest of all learned men, and the most learned of the rich.’  

Cavendish is credited with the discovery of hydrogen, although a later scientist gave that element its name. His paper on Factitious Airs describes ‘inflammable air’ which formed water on combustion. Cavendish also established the composition of the atmosphere, which he said contained phlogisticated air (nitrogen and carbon dioxide), dephlogisticated air (oxygen) and a third element (later known as argon).  

Cavendish’s greatest experiment was to calculate the weight of the earth. The apparatus used was constructed by another scientist, John Mitchell, who died before he could perform the experiment. The device consisted of a torsion balance to measure the gravitational attraction between two 350-pound lead spheres. The extrapolation of the result gave Cavendish what he believed was the earth’s mass. Twentieth Century research proves that Cavendish was accurate to within one percent. His work was later used to calculate Newton’s gravitational constant known as G

Much of Cavendish’s work was never published due to his eccentric antisocial behaviour. Cavendish was certainly solitary and shy leading some commentators to opine that he had Asperger’s Syndrome. Cavendish only allowed one other person in his house, the housekeeper with whom he communicated by notes. He built an extra staircase into the house so that he would not have to meet her in passing.

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