Page:Evolution of the thermometer.djvu/59

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58
EVOLUTION OF THE THERMOMETER.

temperature of melting snow and of the human body, dividing the interval into twelve equal parts. In his paper "Scala graduum," published anonymously in the Philosophical Transactions, May, 1701, Newton gave his method of graduation; he assumed that when the instrument was placed in melting snow the linseed oil occupied 10,000 parts, and found that the same oil at the temperature of the human body, which he called one degree of heat, occupied a space of 10,256 parts; in water boiling violently 10,725 parts, and in melted tin beginning to cool 11,516 parts; from this he computed the degrees of heat corresponding to the phenomena, calling the heat of the human body 12, he found for boiling water 34, and melting tin 72. His thermometer was three feet long and had a bulb two inches in diameter.

Newton also made an experiment with a thick piece of iron as a pyrometer; he heated it red hot and "put it in a cold place where the wind blew uniformly," then he placed on the bar particles of various metals and other fusible bodies and noted the times of cooling, until all the particles having lost their fluidity grew cold, and the heat of the iron was equal to that of the human body. Then by assu-