I 



PROF. HUGH L. CALLENDAR AND MR. HERBERT MOSS 



CHAPPUIS gave a formula of a similar type, to represent the results of his 

 observations by the weight thermometer method between C. and 100 U. 



' 



= {l816904-l-295r266(//100)+11456-2(?/100) 3 } x 10' 



Thia formula has been extrapolated by EUMORFOPOULOS ('Boy. Soc. Proc.,' A, vol. 81, 

 1 1. :S9, 1908), but extrapolation in such a case would be somewhat unreliable. 



The'following table gives a short comparison of the above formulae with formula (8), 

 bowing tin- values of the mean coefficient multiplied by 10 9 , together with the 

 differences from formula (8) : 



TABLE II. Comparison of Formulae. 



A comparison of these differences with those given in Table I. on p. 24 in terms of 

 the same unit, illustrates the state of uncertainty which existed with regard to the 

 expansion of mercury in the year 1907, and may be taken as sufficient excuse for the 

 publication of the present work. 



A similar comparison is shown graphically iu a slightly different manner by the 

 curves in fig. 8. Since it would be impossible to plot the expansion itself graphically 

 on an adequate scale, even by the copper-plate method employed by REGNAULT, the 

 quantity plotted in fig. 8 is the difference of the expansion from lineality, or the 

 difference (a-0'000182054) of the mean coefficient a from the fundamental coefficient 

 multiplied by t. The heavy line with the large circles and crosses represents the 

 results of the present series of observations. The deviations from the curve on this 

 scale scarcely exceed the thickness of the line. The dots surrounded by small circles 

 3 ivpresent RBOXAULT'S actual observations. The broken lines represent the formulas 

 of HK..NAI I.T, WuLLNER, and BROCH. It is evident that the curve representing our ' 

 results also represents REUNAULT'S observations, as reduced by himself, much better 

 than tli,.,y are represented by any of the other three formulae. The difference between 

 the curves given by REGNAULT and WULLNER arises chiefly from the uncertainty 

 alluded to on p. 9 in reducing REQNAULT'S observations to C. The great 

 Aion of BROCH'S curve from the others at high temperatures appears to arise 

 Chiefly from the correction which he introduced in the endeavour to reconcile 



