416 
SECOND REPORT - 1862 . 
try were deduced, and as yet no other principle is recognised 
in the most eminent foreign schools. 
All atomic weights multiples of that of hydrogen. —But in 
Dr. Prout’s well-known paper on the relation between the 
specific gravities and the atomic weights of gaseous bodies, 
another principle was brought under the notice of chemists, 
it was there shown that the atomic weights of such of the 
simple aeriform bodies as had been determined with tolerable 
accuracy were all capable of being represented by some multi¬ 
ple of a common weight, probably of twice the atomic weight 
of hydrogen, by a whole number. The simplicity of this rela¬ 
tion drew the immediate attention of chemists; for, assuming 
it to be a law of nature, it was seen that could we accurately 
determine the true weight of hydrogen, we might at once 
correct all other atomic weights, and if not obtain for each 
substance the precise combining ratio, at least bring very close 
together the extreme limits of error. The analytical researches 
of Dr. Thomson detailed in his First Principles of Chemistry , 
were undertaken with the view of testing this law, and they 
are considered by him as completely establishing it. The mul¬ 
tiplied analyses of Berzelius and other foreign chemists, on the 
other hand, do not coincide with it; and therefore, however 
probable the truth of the law may be, and however desirable 
it would be to have it fully investigated, it cannot yet be con¬ 
sidered as proved. For experimental purposes the numbers 
deduced by the most accurate analysts from careful experi¬ 
ments, though no exact multiple of the atomic weight of hydro¬ 
gen, must still be considered as the standard atomic weights; 
and in this view those of Berzelius are most entitled to confi¬ 
dence. 
Fetation betweeyi atomic weights and specific gravities. —It 
might be supposed that the relation between the atomic weights 
and specific gravities of simple bodies, so ably treated in the 
paper of Dr. Prout already referred to, should aid us in deter¬ 
mining between two numbers differing little from each other, 
and be in fact a test by which the truth of the law above stated 
may be tried. If, for example, 
w - (i 
where W is the atomic weight of any simple substance, G its 
specific gravity in the gaseous state, and G' the specific gravity 
(or half * the specific gravity) of oxygen gas, then, the true spe¬ 
cific gravities being known, the weight of the atom should be 
* If we suppose the volumes of hydrogen and oxygen each to represent one 
atom, G' = the entire specific gravity; if one volume oxygen = 2 atoms G' = i 
specific gravity of oxygen. 
