that connects the Volume of a Liquid with its Temperature. 403 
Thus for Alcohol my observations give E=1717 
»  Sther pS 5 K=1739 
» Sulphate of carbon _,, H=1725 
M. Muncke’s observations on sulphuric acid from 50° to 230° C, 
E=1600 to 1800. (See Note C.) MM. Dulong and Petit’s 
observations on the expansion of mercury between 0° and 300° C. 
give p= ie The line passing through M. Avogadro’s ob- 
servations on the vapour of mercury from 230° to 300° C. gives 
h=1160. These combined give H=1727. I have adopted 
1717 as the nearest probable value at present, because the most 
labour was bestowed on the alcohol series of observations. 
These values of E are derived from English measures of pres- 
sure and temperature, viz. inches of mercury and degrees of 
Fahrenheit scale. The value of this constant derived from French 
measures is F=504°44, which corresponds with H=1717. The 
ah ats Df 3x 29°922 1% bas 
ratio of reduction is a= a4 eee , so that Ka=F, 
a F=2-70282 
rine =0°53195 
ue a 
§ 4. M. Regnault’s observations on the tension of the vapour 
of mercury from low temperatures up to 200° C., respond to the 
same value of / as those at the higher temperatures by M. Avo- 
gadro, but with g augmented 12 degrees, showing a boiling-point 
12 degrees higher. It is remarkable that M. Regnault’s obser- 
vations on the expansion of liquid mercury differs so far from 
those of MM. Dulong and Petit as to be represented with p=4 
and HE=870. At 300° C. this difference amounts to about the 
equivalent of 84° C. The acceleration of the rate of expansion 
is in M. Regnault’s observations only one-half what is shown by 
those of MM. Dulong and Petit. (See Note D.) This 1s a re- 
_markable discrepancy, both being so eminent in this class of ob- 
servations. r 
§ 5. In all cases I have worked with temperatures reduced to 
the air-thermometer by scales of correction computed from the 
formula given in Appendix III. to the paper in the Philosophical 
Magazine for March 1858 above referred to. 
The formula is founded on MM. Dulong and Petit’s observa- 
tions. I annex exact tracings of these scales (Plate VI.). In 
two cases (petroleum and sulphuric acid) the temperatures were 
taken uncorrected and compared with the results when corrected. 
In both, the differences between theory and observation were 
less when the temperatures were corrected. 
2D2 
