XLVIITI PHILOSOPHICAL SOCIETY OF WASHINGTON. 
called attention at the time to “the theory of the process,” he does 
not seem to have apprehended the generality of the principle of 
definite and multiple proportions till a few years later, when the 
doctrine dawned on him in the course of some investigations into 
the constitution of olefiant gas and carburetted hydrogen gas.* 
Richter, before him, had ascertained the quantity of any base 
required to saturate one hundred measures of sulphuric acid, and 
had formed a table exhibiting the proportions of the acids and 
alkaline bases constituting neutral] salts, but Dalton took this table 
and translated it into the relative weights of the ultimate atoms 
composing these saline compounds. 
The doctrine of atomic weights had thus already become a work- 
ing hypothesis in chemistry, no longer an idle speculation, and we 
soon find Berzelius writing to Dalton that “multiple proportions 
are a mystery without it.” { 
From this time onward the history of chemistry has been studded 
with fresh confirmations of the new atomic logic, while ever and 
anon prophetic glints of truth, implicit in every true physical 
hypothesis, have leaped into the light of ocular demonstration 
with each advancing stage in chemical science. Time would fail 
to tell the beads of the atomic rosary. The doctrine of fixed, 
multiple, and volumetric combinations, as formulated by Avo- 
gadro in 1813;§ the determination of the proportions in which 
bodies combine according to the number and disposition respect- 
ively of their molecules, as announced by Ampére in 1814, with 
special reference to the clear-cut distinction between molecules 
and their integrant atoms, (already presaged before Ampére by 
Laurent and Gerhardt;) || the relation between the atomic weights 
of bodies and their specific heats, conjectured by Dalton and estab- 
lished by Dulong and Petit in 1819;9] the law of isomorphism, an- 
nounced by Mitscherlich at the close of the same year, from which 
it appeared that “a similar atomic constitution determines not only 
*Henry: Memoirs of the Life and Scientific Researches of John Dalton, 
p- 80. 
+ Ibid., p. 85. 
t Ibid., p. 100. 
2 Wurtz: The Atomic Theory, p. 36. 
|| Annales de Chimie, vol. 90, p. 48. 
q Wurtz: The Atomic Theory, p. 52. 
