THE EVOLUTION OF THE THERMOMETER. 415 



ton introduced his linseed-oil thermometer, taking the zero 

 as the temperature of thawing snow, and 1 2° as that of the 

 blood of a living animal. In a "translation from the 

 Latin" — apparently of a paper by Newton — in the Philo- 

 sophical Transactions for 1 70 1 , vol. xxii., p. 824, there is a 

 "table of the degrees of heat," the lower temperatures 

 being presumably taken with the oil thermometer, and the 

 higher by comparison with heated iron. In this table, o° is 

 the temperature of freezing water, 1 2 blood heat, and 34° 

 that of strongly boiling water; 192 was the heat of 

 live coals burning in a kitchen fire without the aid of 

 bellows. 



A thermometer which is said to have drawn Fahrenheit's 

 attention to the subject of the graduation of thermometers, 

 is said to have been described bv M. Amontons in the 

 Mchnoircs de £ Academie Royale de Paris in 1701 or 

 1702, although the writer has been unable to find the 

 paper in these Mdmoires. In Amontons' thermometer, by 

 which he is frequently credited with having first shown that 

 the boiling point of water is constant, a long glass tube was 

 turned upwards at the bottom and terminated there in a 

 bulb. The bulb contained air, and the tube contained 

 mercurv which formed the indicator. The tube was 

 graduated— on the assumption that the atmospheric 

 pressure is equal to a pressure of twenty-eight inches of 

 mercury — in inches and parts of an inch. The highest 

 point, forty-five inches above the level of the mercury in 

 the bulb, was numbered seventy-three, i.e., the height 

 above the mercury plus the atmospheric pressure. His 

 thermometer was thus extremely long and cumbrous, and 

 was inaccurate owing to no allowance being made for varia- 

 tion of atmospheric pressure. 



The Fahrenheit thermometer was first graduated with 

 a scale of 1S0 , the zero being described as " temperate ' : 

 and corresponding with 9 of the present centigrade ther- 

 mometer, 90 being " blood heat," and - 90 being the tem- 

 perature of a mixture of ice and salt, supposed to be the 

 greatest degree of cold obtainable. In 17 14, at the sugges- 

 tion of Claus Roemer, Fahrenheit changed his zero to the 



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