WILLIAM G. STEVENSON. ia 
light from the secret chambers of distant space, and from 
them learned the history of the stars. 
The imagination of Laplace, leaping beyond the limits 
of sensory perception, saw cosmic matter ‘‘ without forna 
and void’’ integrating into worlds, and law and order 
were seen reigning throughout the material universe. 
Astrology had been supplanted by astronomy. While 
physical philosophy was thus engaged in measuring 
space and magnitudes, and interpreting the laws of cos- 
mic phenomena, its companion science, chemistry, was 
slowly putting aside the swaddling clothes of alchemy, 
which had so long—though vainly—sought to trans- 
mute the baser metals into gold, to discover the philoso- 
pher’s stone, and find the elixir of life. Alchemy did 
not analyze substances; it simply decomposed them : 
and it had no knowledge of the ultimate composition of 
the different forms of matter. 
Paracelsus and Van Helmont, even Boyle and Stahl, 
although innovators of the ‘‘sacred art,’’ were but the 
‘incubators of chemistry.’? And not until the balance 
and the test-tube, in the hands of Black, Priestly, Cav- 
endish, and Scheele, had, by analysis, laid the founda- 
tion of quantitative chemistry, was the hope justified that 
the intrinsic properties of matter, and the laws of 
atomic combinations, would be revealed. 
New facts, through analysis, accumulated, until Dal- 
ton, in 1804, suggested the atomic theory as a new 
means of interpreting phenomena. ‘This theory was 
soon promulgated under the generalization known as 
the law of Avogadro or Ampére; and from this dates 
the birth of modern chemistry. 
When Rumford and Davy experimentally demon- 
strated that. heat was but a ‘‘mode of motion,’ and 
when Joule, in 1850, determined its mechanical equiva- 
lent, and established the law of thermo-dynamics, it was 
for the tirst time possible to make a classification which 
