84 
PEOFESSOE KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 
far there is a difference in the first metal according as it has been heated or hammered, 
and in the second, according as it is soft or hard. It may be compared with a gonio- 
meter, which not only measures the angles of a crystal, but also the differences in the 
angle produced by heat ; or it may be compared to a method for determining the specific 
gravity of a body, by which not only this property, but also its changes with the tem- 
perature may be determined. But along with such methods, simpler ones, though 
perhaps less accurate, have also their value. Which method is the most convenient or 
which ought to be used in a given case, depends on the question to be decided by the 
experiment, or on the extent to which the property in question is constant in the sub- 
stance , examined. 
In regard to the relations of the specific heat of solid bodies to their atomic weight 
and to their composition, Regnault’s determinations have shown that both Dulong 
and Petit’s and Neumann’s law are only approximate, and that even the accuracy in 
determining the specific heat which Regnault attempted, and obtained, could not show 
that these laws were quite accurate. 
Although the description of Regnault’s mode of experimenting is so widely known, yet 
it cannot be said to have become the common property of physicists, or to have found 
an entrance into the laboratories of chemists, to whom the determination of the specific 
heat is interesting from its relation to the atomic weight. Very few experiments have 
been made by this method other than the determinations of Regnault. The method 
depends on the use of an apparatus which is tolerably complicated and takes up much 
room. Each experiment requires a long time, and for its performance several persons 
are required. Regnault has usually worked with very considerable quantities of the 
solid substance, and in by far the majority of cases at temperatures (usually up to 100°) 
which many chemical preparations, whose specific heats it is important to know, do not 
bear. In the sequel I will describe a process, for the performance of which the 
apparatus can be readily constructed, and for which one operator is sufficient ; by which, 
moreover, the determination of specific heat can be made with small quantities of the 
solid substance and at a moderate temperature. But the method as I have used it has 
by no means the accuracy of that of Regnault. In § 18 I shall discuss the advantages 
for which some of the accuracy which characterizes Regnault’s method is sacrificed ; but 
I may here remark that the results obtained by the method which I have used are 
capable of increased accuracy, provided the experiments are executed on a larger scale 
and within greater ranges of temperature. 
17. The principle which forms the basis of my method is as follows: — To determine 
the total increase of temperature produced when a glass containing the substance to be 
investigated, covered by a liquid which does not dissolve it, the whole previously warmed, 
is immersed in cold water ; to subtract from the total increase of temperature that due 
to the glass and the liquid in it, and to deduce from the difference, which is due to the 
solid substance, its specific heat. 
If, in regard to gain or loss of heat, the glass, in so far as it comes in contact 
