Chemical Effects of Caloric, $c. 61 



periments of Mr. Dalton of Manchester, it was 

 found that all gasses, or aeriform fluids, undergo 

 the same expansion by the same degrees of heat, 

 supposing the circumstances the same. It may 

 be useful to note, that he found by his experi- 

 ments that 100 parts of air by being heated from 

 55 to 212" expanded to 132|. The steam of 

 water and the vapour of ether undergo the same 

 expansion with air when the same addition is 

 made to their temperature: hence all elastic 

 fluids may be said to expand equally and uni- 

 formly by heat. 



What is remarkable, bodies, though expanded 

 by caloric, never suffer any increase of weight 

 from its presence. Muschenbroeck says that iron 

 when heated loses 1-1 00th part of a grain in the 

 cubic inch, and the same quantity of lead loses 

 4- grains, but when cool they return to their 

 former weight. This loss of weight, however, is 

 rather owing to the rarefaction of the air round 

 the scale ; the pressure of the atmosphere on 

 the scale being lessened, the metal weighs 

 lighter ; the heat might also expand the side of 

 the beam, and render it false. 



When we speak of the specific gravity of bo- 

 dies, we ought to mention the degrees of heat ; 

 for the specific gravity is different in winter and 

 in summer, and this is owing to the expansion 

 of the body by the presence of a larger quantity 

 of caloric. Boerhaave supposes that air, which 



