92 
PKOFESSOE KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 
of the other thermometer, the reduced value of which might be neglected under these 
circumstances. These experiments gave 0T6 as the reduced value of the thermometer 
r, and 0T7 as the reduced value of the thermometer b. The thermometers have very 
nearly the same dimensions. Hence I put the reduced value of the calorimeter (that 
is, of the part of the metal concerned), of the stirrer, and of the immersed part of the 
thermometer at 1*04 grm. Even if this determination is a few tenths out, it is scarcely 
appreciable as compared with the quantity of water in the calorimeter. In all following 
experiments this was between 25-85 and 25-95 grms. 
All the subsequent determinations depend on fixing differences of weights and of 
temperatures. The accuracy of the results depends on the precision with which both 
kinds of magnitudes are ascertained ; and it is useless to determine the weights to ywoo 
or nearer, if the differences in temperature cannot be determined more accurately than 
to -200 or - 3 ^ 0 . I have weighed to centigrammes instead of to milligrammes, by which 
the time necessary for the weighings was much shortened, and their accuracy not 
materially lessened. 
22. The reduced value x remained to be determined of the glasses (cylindrical tubes 
of thin glass, see § 17), or, rather, of that part which was immersed in the water of the 
calorimeter, the quantity of which was always the same. In the following, T is the 
temperature to which the glass in the mercury-bath was heated (compare fig. 1), M the 
quantity of water in the calorimeter + the reduced value in water of the other parts of 
the latter, which required to be taken into account, t the temperature of the water in 
the calorimeter when the glass was immersed (fig. 2 ), and r the temperature to which 
the water became heated, and which must be considered as that to which the glass 
cooled*. We have then 
M(r-<) 
X ~ T-r 
In my experiments I used three glasses, which may be called 1, 2, and 3. To ascer- 
tain the reduced value of glass 1 , I made the following determinations : — 
Temperature of Air 15°-8. 
T. 
r. 
t. 
M. 
X. 
0 
0 
grms. 
78-54 
17-23 
15-72 
26-98 
0-664 
74-38 
17-16 
15-78 
26-97 
0-651 
75-51 
17-14 
15-72 
26-92 
0-655 
76-06 
17-15 
15-73 
26-945 
0-649 
77-32 
17-22 
15-74 
26-96 
0.664 
Mean . 
. 0-657 
* If the cork which closes the glass, and by means of the wire passing through it enables it to he handled, is 
moist, incorrect and discordant values are obtained for it, owing to the evaporation of water in the empty 
glass so iong as this is in the mercury rbath, and to the condensation of aqueous vapour in the glass when it is 
immersed in the calorimeter. 
