4g2 PHILOSOPHICAL TRANSACTIONS. [aNNO I76O. 



atmosphere; the same liquor will receive 8 or 9° of heat more than when the 

 barometer is at the lowest. But whether this proceeds entirely from the liquor's 

 receiving a greater degree of heat by the pressure of the atmosphere may be a 

 matter of some doubt; as it seems, by comparing the mercurial with other ther- 

 mometers, to be affected in some measure by the pressure of the atmosphere in 

 all degrees of heat and cold. 



The making of metalline thermometers has been hinted at by many ; parti- 

 cularly by Mr. Smeaton in his curious observations on the expansion of metals, 

 who recommends zink or spelter as most capable of expansion, and fittest for the 

 purpose. Mr. F, has endeavoured to make one on this principle, which he lays 

 before the Society, with a description of its construction, and an account of the 

 few observations he had been able to make on it. 



The structure of this instrument is very intricate and delicate, and in use is 

 hardly practicable. Mr. F. acknowledges, that since this instrument has been 

 made, he found in the Phil. Trans., that Dr. Mortimer had in 1735 given the 

 R. s. a description and drawing of an instrument he invented for the purpose ; and 

 that Mr. Johnson had also given a drawing of another, invented by Mr. Fo- 

 thringham. 



Mr. F. finds, by comparing this instrument with a Fahrenheit's and a spirit 

 thermometer, that it keeps at a medium between both ; not rising at first so 

 quick as the mercury, and somewhat quicker than the spirit. On placing them 

 together in the sun, when its heat became intense, it rose at last faster than the 

 mercury, and not so fast as the spirit; and it continued to rise for some time 

 after the others became stationary. 



He tried the expansion of a few metal bars, from artificial freezing, with 

 pounded ice, and water that it dissolved into; on which was poured half an ounce 

 of spirit of tartar, in which Fahrenheit's thermometer descended to within one 

 degree only of the freezing point: to boiling water, in which it rose to 211°, 

 though the water did but scarcely boil, for want of a sufficient number of lamps. 

 The barometer stood at 30 inches, and the natural heat of the weather at 60° of 

 Fahrenheit. 



Divisions. 



A bar of spelter 2 feet long, marked by the minute index . . . 1570 



Spelter 1 8 parts, and copper 2 parts 1150 



Brass 1120 



Iron 785 



Steel 695 



Note. Each division marks the 73840th part of an inch expansion per foot. 



Mercury cannot be useful in trying any degrees of heat above what makes it 

 boil ; and it appears by Dr. Hinsell's account of the experiments lately made at 



