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The eminent French physicist, Guillaume Amontons, lost his hearing when a schoolboy, and like the philosopher of old who destroyed his eyesight for fear visual impressions should disturb his speculations, the Frenchman declined surgical and medical assistance lest the admission of common noises to his brain should interfere with his profound studies in mathematics and mechanics. He became skilled in surveying, able in architecture and distinguished in pure mathematics, and he made important improvements in the hygrometer, the barometer, and the thermometer.

Amontons constructed the first veritable air-thermometer which was not at the same time a barometer; it consisted of a narrow glass tube four feet long, open above, ending below in a large bulb connected by a U-shaped bend; in this bulb air was confined by a column of mercury so adjusted that when the apparatus was immersed in boiling water, the barometer standing at 28 inches, the mercury in the tube stood 45 inches above the level in the bulb, thus making the pressure of the heated air 73 inches. The tube was graduated from 73