ANNALS 
oF 
PHILOSOPHY. 
MARCH, 1819. 
ArTIcLeE I. 
Researches on the Measure of Temperatures, and on the Laws of 
the Communication of Heat. By MM. Dulong and Petit. 
(Continued from p. 124.) 
_ Of the Dilatation of Solids. 
IF we compare the results of the preceding table with those 
that we have given in Table I, it will be seen that the doubts 
which we raised respecting the rate of the mercurial thermo- 
meter were not without foundation ; and that the laws of the 
dilatation of the envelope of this instrument, and of the liquid 
which it contains, are very distinctly different, when we consider 
a great interval of temperature. When the air thermometer 
marks 300° on its scale, mercury taken absolutely would mark 
314°15°; while the common thermometer only marks 307-649. 
The preceding determinations are so much the more interest- 
ing, because they may lead to the knowledge of the absolute 
dilatation of several solid bodies. Nothing more is necessary 
than to ascertain the difference between the expansion of mercury 
and each of these bodies. 
This is easily obtained with respect to glass ; for the differ- 
ence in question is merely the apparent dilatation of mercury in 
that body. Though this dilatation has been already the object 
of a great many determinations, we have thought it necessary to 
undertake it ourselves with all the care that such experiments 
require. For this purpose, we employed a tube of about 6 
decimetres inlength, and capable of holding about 700 grammes 
of mercury. This tube was shut at one of its extremities, and 
Vor, XIII. N° III. I, 
