It On Light and Heat. 



Fahrenheit's 

 scale. 



Human blood freezes - - 25 



Strong wines freeze - 20 



Below zero. 



A mixture of snow and salt freezes to 4 



Brandy, of equal parts of alcohol and 



water, freezes - - 7 



Proof spirit, in Reaumur's thermometer, 



froze at Tornedo - 34 



Mercury freezes - - 39 to 40 



Cold, produced by Mr. Macknab, at 

 Hudson's-Bay, by a mixture of sul- 

 phuric acid and snow - 69*. 



Heat — its fwofold state — curious effects. — Light and 

 Heat — their great importance. 



It still may be not improper to observe, that the 

 thermometer does not give the absolute heat con- 

 tained in bodies, nor any sign of its presence while 

 in the quiescent state, nor till it be evolved in the 

 sensible form ; also that our sensations of heat and 

 cold are only relative terms, and apt to deceive us, 



* Encyclopxdia. Philadelphia. Vol. XVIII. article Therm. 

 N. B. This experimenl is said to have been made on 24th De- 

 cember, 1804, with a spirit thermometer. 



