164 Dulong and Petit on the Measure of Temperatures, (Marcu, 
TABLE IV. 
pry p ae) ee a eee ee 
indi indi fi indicated 
‘Temperature heolute|Pe™p- indicated] ean absolute Temp. indicated] yean absolute | /e™P: im 
Gediced from ES eae pris byathermometer dilatation of ibyathermometer dilatation of pla- hd pa ate 
the dilatation iréw made of # bar of copper. ade of a copperliinum, made of a plati- 
of air. ; iron, id. num rod. 
TA cl I lei ET 17 le 
S00 «vere eeniled gi Gicd. cataanelt te. Mvempaebesl iG 
m 
ro 
When we compare these results with those which we have 
already obtained for glass, we see that the dilatability of solids, 
referred to an air thermometer, is increasing ; and that it is 
unequally so in each of them. This consequence, which we 
have already pointed out in the memoir above quoted, is now, 
therefore, fully confirmed. r 
We conceive that we have attained in what precedes the 
highest degree of accuracy consistent with such delicate 
measurements. This becomes evident by comparing the num- 
bers which we give for the dilatation at 100°, with those which 
have been given by Lavoisier and Laplace. We shall add only 
a single observation. In the direct measurement of the dilata- 
tion of solids, the uncertainty is tripled, when we pass from 
linear expansion to expansion in volume. As our determinations 
give this last immediately, the error committed is not increased. 
Of the Specific Heat of Solids at different Temperatures. 
From the results of the preceding researches, we see that 
if we refer a series of any phenomena whatever to a thermometer 
taken successively from the gases, the liquids, and the solids, 
each species of instrument would lead to a particular law. It is 
not then indifferent to employ any thermometer whatever, if we 
wish to arrive at the most simple law; or if we wish to represent 
the phenomena by measures which have from their nature the 
most direct relations with them. But to be able to determine 
in this respect, we must know how much the capacities of all 
‘bodies vary in each of the thermometric scales which we have 
made known. 
From the time that Black established the notion of capacities, 
a great number of philosophers have endeavoured to attain 
greater and greater precision in the numerical determinationg 
relative to each substance, and to include in their tables bodies 
not hitherto subjected to experiment. The experiments of Wilke, 
of Crawford, ot Meyer, and especially of Lavoisier and Laplace, 
are, as is known, the most remarkable of all those which have 
been published on this subject. Deluc and Crawford, supposing 
an ideal thermometer in which the capacities were constant, 
compared its indications with those of a mercurial thermometer 
to judge of the accuracy of this last... Almost all their experi- 
ments are referable to mixtures of liquids, below the temperature 
