8 EXPANSION OF LIQUIDS. 



limb, kept at a constant temperature. The columns of course 

 balance each other, and the shorter column of dense fluid sup- 

 ports a longer column of dilated fluid. All other modes of ob- 

 taining the absolute expansions of liquids are fallacious. 



No progress has yet been made in discovering the law by 

 which expansions of liquids are regulated ; for the complicated 

 mathematical formulae of Biot, Dr. Young, and others, are mere 

 general expressions for these expansions, which proceed upon 

 no ascertained physical principle. Some theory must be formed 

 of the constitution of liquids, before we can hope to account for 

 their expansions. 



Count Rumford ascertained the contraction of water for every 

 22J, in cooling from 212 to 32. The results were as follows, 

 2000 measures of water contract 



In cooling 22j", or from 212 to 189 \ . 18 measures. 



189* 167 16.2 



167 144i . 13.8 



144J 122 .11.5 



122 99i . 9.3 



99* 77 7-1 



77 54 - 3.9 



54i 32 . 0.2 



The expansion of water, by heat, is subject to a remarkable 

 peculiarity which occasions it to be extremely irregular, and 

 demands special notice. This liquid, in a certain range of tem- 

 perature, becomes an exception to the very general law that 

 bodies expand by heat. When heat is applied to ice-cold water, 

 or water at the temperature of 32, this liquid, instead of ex- 

 panding, contracts by every addition of heat, till its temperature 

 rises to 40 at, or very near which temperature water is as dense 

 as it can be. And, conversely, when water of the temperature of 

 40 is exposed to cold, it actually expands with the progress of 

 the refrigeration. Water may, with caution, be cooled 20 or 25 

 degrees below its freezing point, in the fluid form, and still con- 

 tinue to expand. It is curious that this liquid, in a glass bulb, 

 expands as nearly as possible to the same amount, on each side 

 of 42 when either heated or cooled the same number of degrees. 

 Hence when cooled to 40 it rises to the same point in the stem 

 as when heated to 44 ; at 32 it stands at the same point as at 

 52, and so on for different temperatures, as illustrated in the 

 graduation of the figure. The expansion of water by cold, under 



