PROCEEDINGS 
OF THE 
ROYAL SOCIETY OE EDINBURGH. 
yol. iy. 1859-60. No. 51. 
Monday , 19 th December 1859. 
DAVID MILNE HOME, Esq., in the Chair. 
The following Communications were read : — 
1. Note on some Numerical Relations between the Specific 
Gravities of the Diamond, Graphite, and Charcoal Forms 
of Carbon and its Atomic Weight. By Dr Lyon Playfair, 
C.B., F.R.S. 
Recent researches have shown that there is an intimate relation 
between the specific gravities and atomic weights or equivalents of 
solid and liquid bodies. This relation is not so simple as that which 
prevails in regard to the volumes and combining numbers of gaseous 
bodies, and yet it is sufficiently marked to indicate many important 
chemical analogies. The formula for eliciting these relations is — 
in which E is the equivalent, d the specific gravities, and V the 
atomic volume. 
It is to be borne in mind, that the unities or starting-points for 
specific gravities and for atomic weights are essentially distinct. In 
VOL. iv. 2 K 
