804 
chemical changes, namely, fire or combus- 
tion. It was noticed that there are two 
classes of bodies, those that will burn and 
those that will not. The former were as- 
sumed to contain the element of fire or 
phlogiston. In the process of burning the 
phlogiston was supposed to escape into the 
air; the ashes or products of combustion 
remained behind. The act of burning was 
looked upon as a decomposition. Combus- 
tible bodies were all supposed to be of a 
compound nature, consisting of phlogiston 
and the products of combustion. In the 
act of burning these two elements separated, 
the phlogiston going off into the air, the 
products of combustion remaining behind 
as the ashes. 
This first theory of chemistry was re- 
placed by a better one in the year 1785 by 
Lavoisier, the distinguished French chemist. 
Last summer a bronze statue of Lavoisier 
was unveiled in Paris. It bears a single 
inscription, namely, ‘The founder of Mod- 
ern Chemistry.’ Lavoisier found that 
when bodies burned the products of com- 
bustion were heavier than the original sub- 
stances. A few years previous to this, in 
1774, Joseph Priestley, the English clergy- 
man, had found that when the red calx of 
mercury is heated oxygen gas is obtained, 
and that substances burn very brilliantly 
in this gas. Lavoisier repeated the experi- 
ments of Priestley, saw, what the latter 
failed to see, that burning was the union of 
oxygen with the burning substance and that 
combustion was a chemical combination 
and not a decomposition. ‘There is no 
such thing as phlogiston, the element of 
fire,’ said Lavoisier; and from this time 
on all substances that could not be resolved 
into simpler substances weighing less than 
the original substances were called elements. 
Thus began a new era for chemistry, a 
quantitative era, in the year 1785. From 
now on the balance became the chief in- 
strument of chemical investigation. Such 
SCIENCE. 
[N. 8S. Vou. XIII. No. 334. 
in brief was the condition of chemistry one 
hundred yearsago. The ideas of Lavoisier 
had,at the opening of the last century, come 
to be very generally accepted, but very 
little was known beyond these. Oxygen 
was the chief element and the oxides the 
chief compounds or, as Berzelius said : 
‘ Oxygen was the center point about which 
chemistry revolved.’ The knowledge of 
the composition of other substances was 
very imperfect. It was not even known at 
that time that substances do have a fixed 
composition ; indeed the fundamental laws 
of chemical action were still all undiscov- 
ered. Almost nothing was known of the 
composition of substances of vegetable or 
animal origin, that great and important 
class of bodies that we now know as organic 
substances. A century ago it was not 
known that alcohol contained oxygen; this 
fact was found out in the year 1809. There 
were no laws and principles, no general- 
izations ; chemistry consisted of purely de- 
scriptive matter, and that was often very 
imperfect. Inorganic chemistry was largely 
mineralogy, organic chemistry was chiefly 
botany. 
Limited as chemical knowledge was when 
the nineteenth century opened, there were, 
however, certain men at work, who had 
adopted the quantitative methods of Lavois- 
ier, and who soon made important discov- 
eries. First of all Proust, in 1801, an- 
nounced that every chemical compound has 
a fixed and definite composition, that when 
substances unite chemically they do so in 
definite ratios by weight. This statement 
of Proust’s was not allowed to go unchal- 
lenged. C. L. Berthollet maintained that 
compounds have a variable composition, 
and that if there are any that do appear to 
have a fixed composition itis an exception 
and not the rule. For eight years the con- 
troversy was carried on between these men. 
Proust finally came out victorious. More 
and more analyses of compounds were made, 
