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[April, 
CORRESPONDENCE. 
RESIDUAL PHENOMENA. 
To the Editor of the Quarterly Journal of Science. 
Sir, — In the article on “ Residual 
Phenomena” published in the last 
issue of your Journal it is stated that 
the adtual atomic heats of carbon, 
boron, and silicon are much lower 
than those required by the law of 
Dulong and Petit, and it is assumed 
that there is some residual phenome- 
non modifying the result in these 
three instances. It is also stated that 
“ though the anomalies to which we 
have drawn attention have been re- 
cognised for more than a quarter of 
a century, the explanation is still 
wanting.” 
I would draw the author’s atten- 
tion to the researches of F. Weber 
respecting the specific heats of the 
three above-mentioned elements (Ann. 
Chim. Phys. [5], viii. ; abst. Journ. 
Chem. Soc., June, 1876). Weber 
found that the specific heats of these 
bodies increase rapidly with the tem- 
perature, and at high temperatures 
tend to become constant. If we 
multiply the specific heats at these 
high temperatures into the atomic 
weights, we obtain the atomic heats. 
Carbon — (1) diamond, 5’5 ; (2) gra- 
phite, 5*6 ; silicon, 5-75 ; boron, 5-5. 
Thus it appears that the true atomic 
heats of these three elements do not 
vary from the mean number 6 ’y to a 
greater extent than those of other 
elements of low combining weight, 
such as aluminium. 
Here, then, we have the residual 
phenomenon alluded to ; and it is 
interesting to note that its explana- 
tion affords a further confirmation of 
Dulong and Petit’s law. — I am, &c., 
C. H. Bothamley. 
The Yorkshire College, 
February 20, 1878. 
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