248 ON THE EXPANSION BY HEAT OF WATEE AND MERCUET. 



In Series V. the water was boiled before each obser^'ation, and the water in the box 

 stin-ed during the time of weighing. 



In the beginning of this paper I stated that my reason for carrying out the foregoing 

 research was that, basing my calculations on Kopp's coefficients of expansion of water, 

 I could not obtain a value for the coefficient of mercury which agreed with Regnault's. 



If we deduce this value from Tabic XII., using Kopp's coefficients, we find, of course 

 taking the volume of water at 4°=1, the volume 



U,=U„(1+0-0001780. 



The same deduced from calculations based on the values in Table X., 



U,=U„(l + 0-0001812^). 

 Eegnault found by direct measurement the expansion of mercury to be 



U,=U„(1 + 0-0001815!;). 



On comparing the values given in Table XI., it will be seen how closely Despretz's 

 and the last series agree, whereas Kopp's and Despretz's results do not agree, although 

 obtained by the same process. Bearing these facts in mind, we must conclude that 

 Kopp's coefficients for the expansion of water are too low, (1) as the coefficient of expan- 

 sion of mercury falls below that found by Regi^ ault when deduced by means of Kopp's 

 coefficient ; (2) as the said coefficients are lower than those obtained by other observers ; 

 and (3) as the coefficient of mercury when deduced by means of those obtained for water 

 by the above-mentioned observers agrees closely with that found by Eegnault ; for had 

 I employed Despretz's coefficients instead of my own, I should have deduced very nearly 

 the same value for the coefficient of expansion for mercury. 



In conclusion I may be allowed to express my thanks to the gentlemen who have 

 assisted in carrying out the foregoing research ; to Professor Hirst for his kindness in 

 suggesting methods of reduction and calculation, to Mr. Bassett and Dr. Max Berexd 

 for the able manner in which they assisted in the experimental part, and to Dr. C. Vogt 

 for his undertaking the greater part of the computations. 



