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38 about one-fifth of the common air, are turned into pure water." He further showed that when dephlogisticated air (oxygen) and inflammable air (hydrogen) were exploded together, pure water was the result.

Although he proved the composition of water, it does not appear that he viewed it as a chemical compound of the two gases. His phlogistic ideas biased even his clear mind to such an extent that, after the overthrow of the phlogistic doctrine by the work of Lavoisier, he withdrew from any active part in scientific research.

In 1783, in a letter to Black, James Watt expressed the opinion that "water is composed of dephlogisticated and inflammable airs." A long and bitter controversy raged about the discovery, the priority of which was claimed for Watt. It is now, however, universally ascribed to Cavendish.

Although nitric acid was known to Geber—the eighth-century alchemist—Cavendish proved (1784-85) the exact composition and mode of formation of this acid. He was remarkable for the accuracy and precision of his experimental discoveries; but any attempt to draw him into conversation was useless. "The way to talk to Cavendish," said Wollaston, "is never to look at him, but to talk as it were into vacancy, and then it is not unlikely you may set him going."

In 1766 Cavendish discovered inflammable air (the hydrogen of to-day), producing it by the action of dilute