86 Mr. II. C. Sorby on the Expansion of Water 



length of the bubble, I heated the tube in a bath of water or 

 paraffine to 0°, 25°, 50°, 75°, 100°, 125°, 150°, 175°, and 200°C., 

 and carefully measui-ed the length of the bubble at all those 

 temperatures ; and I took care to repeat the measurements in 

 descending order, and to adopt the mean of both, so as to com- 

 pensate for the slight but very notable action of the water on 

 the glass at the highest temperatures. I have employed the 

 Centigrade scale, because it makes the formulae so much more 

 simple, and has been used by all the previous experimenters 

 already referred to. 



The various data described above give only the apparent ex- 

 pansion, and require some correction before we arrive at the real 

 expansion. To the apparent expansion of the liquid must be 

 added the expansion of the glass, which would be about "0026 

 for each 100° C. ; and moreover it is requisite to make allow- 

 ance for the diameter of the bubble in the tube being not quite 

 so great as that of the column of water, becavise the sides of the 

 tube were wet and covered by a film of water, which, according 

 to my experiments, was about -nuToth of an inch in thickness. 

 Having applied all these corrections, I found that the volume of 

 water was as follows : — 



It will thus be seen that the second difference is not constant 

 for temperatures above 25°; but no doubt this is in great measure 

 due to errors in the observations, for the third difference is very 

 irregular. Still the second difference is greater at high than at 

 lower temperatures, but not so much so as to make it quite cer- 

 tain that a term involving t^ ought to be taken into considera- 

 tion. Possibly that, and even still higher powers, might more 

 accurately express the true law of the expansion, and their in- 

 riuence may be masked by the increasing rate of the expansion 

 of the mercury of the thermometei-, or of the glass of the tube ; 

 but, since the water begins to act on the tube at these high tem- 

 peratures, it is almost impossible to determine the volume so 

 accurately as to remove all doubt. Taking into account the 

 temperature included between 25" and 175°, I deduce the follow- 



