164 
structure of the difterent crystals indicate ; and what makes 
this fact very interesting is, that there is no case known at 
all similar, with respect to any other elementary body. 
There is one fact of very great theoretical importance 
connected with these relative volumes, viz., their specific 
heat. In the case of charcoal and diamond I had predicted 
a considerable time before I knew that it was so, that their 
relative specific heats would be as 2 : 1 ; and such is really 
the case. Moreover, the specific heat of coke and graphite 
is the same, whereas it is to that of diamond as J : J, and to 
that of charcoal as ^ i ; whence it will be seen that the 
specific heat of the four species of carbon is in precisely the 
same ratio as the volume of their atoms ; or in other words, 
the capacity for heat of the atoms of carbon, when of difier- 
ent volumes, varies in the same ratio with their magnitudes, 
which I believe to be an entirely new law as regards an 
elementary body. To render these facts more apparent I 
subjoin the following table, which is calculated from the found 
mean specific gravity and heat of the square prismatic form : 
Square 
Prism- 
atic form 
Coke. 
Graphite. 
Diamond. 
Specific gravity — 
1 
Theory 
2Xv/2 
3 X 1 
3 X ^/f 
4 X \/ 2 
1.773 
1.880 
2.172 
3.546 
Experiment 
1.773 
1.891 
2.177 
3.521 
Comparison of theory 
and experiment ... 
Relative volume of 
... 
ylo too little 
^igtoo little 
j-igtoomuch 
atoms 
1. 
i 
1 
i 
2 
3 
3 
4 
Specific heat — 
i, 
.1357 
Theory | 
4 
.2714 
3 
.1809 
i 
.1809 
Experiment 
.2714 
.2028 
.2019 
.1331 
Comparison of theory 
too much 
and experiment ... 
... 
^ too little 
^ too little 
Note. — In this table, in the upper line of figures, the number on the left hand 
side of the X indicates the inverse volume of the atoms ; and that on the 
right the correction required for difference in crystalline form and arrange- 
ment of the atoms. 
