242 
the first case, the weights of the bodies are compared with the 
weight of an equal bulk of water ; in the second instance, the com- 
bining numbers refer to a unit weight of hydrogen. Nevertheless, 
the relations observed between the specific gravities and the atomic 
weights are well marked in bodies of a like character. 
It has always been considered interesting to examine these rela- 
tions in regard to Carbon, which has three well-characterised allo- 
tropic forms. The atomic volumes obtained by the above formula 
show no satisfactory relations between the numbers obtained for 
each of the states in which the element presents itself. 
Before we examine them in another way, it is desirable to obtain 
a mean specific gravity for the Diamond, Graphite, and Charcoal, as 
the recorded results of experiment show a considerable variation. 
1. Diamond. 
The specific gravity of this gem is generally stated in elementary 
works to range from 3 "5 to 3*55 ; but these numbers do not repre- 
sent the mean of recorded experiments, as will be seen by the fol- 
lowing table : — 
O 
Diamond in Hunterian Museum, Glasgow, 
3-53 
Thomson. 1 
Specific gravity, as stated by Mohs, 
3-52 
Mohs. 2 
Brazilian diamond, 
Another variety of the same, . 
3*44 'j 
3-52 J 
Brisson. 3 
Mean specific gravity of a “ beautiful collec- 
tion of diamonds,” . . . 
^ 3-48 
Lowry. 4 
“ Star of the south,” 
3'53 
f Dufrenoy & 
l Halphin. 6 
Borneo diamond, 
3*49 
Grailich. 6 
Do. do., compact, 
Do. do., do., 
3*41 1 
3*25 J 
1- Bivofc. 7 
1 Thomson’s Mineralogy, vol. i. p. 46. 
2 Mohs’ Mineralogy, vol. ii. p. 306. 
3 Brisson, as quoted by Bottger, Specifiche Geiwicht., p. 32. 
4 Lowry, as quoted by Thomson’s Mineralogy, vol. i. p. 46. 
5 Dufrenoy, Compte Rendu, vol. xl. p. 3. 
0 Grailich Bull. Geol. [2], vol. xiii. p. 542. 
7 Rivot, Ann. des Mines, vol. xiv. p. 423. 
