SEPTEMBER 1, 1899.] 
them, as fire or water. The Thalesian 
theory deriving all things from water was 
especially popular and was not completely 
overthrown until the modern era. 
When, later on, the alchemist conceived 
of all metals as composed of sulphur and 
mercury it was an essence or spirit of mer- 
cury that was meant. Certain common 
characteristics as luster, malleability, fusi- 
bility, combustibility, etc., naturally led 
them to think of the metals as belonging to 
the same order of substances containing 
the same principles, the relative propor- 
tions and purity of which determined the 
variations in the observed properties. Thus 
the properties of the metals depended upon 
the purity of the mereury and sulphur in 
them, the quantities of them and their de- 
gree of fixation. The more easily a metal 
was oxidized on being heated, the more sul- 
phur it contained, and this sulphur also 
determined its changeability. The more 
malleable it was, the more mercury entered 
into its composition. If only something 
could be found which would remove the 
grossness from these essences, some un- 
changing, all-powerful essence, which, be- 
cause of their search for it, gradually became 
known as the ‘ philosophers’ stone,’ then the 
baser metals might be transmuted into the 
noble gold when the sulphur and mercury 
were perfectly balanced and free from all 
distempers. 
As has been said, these principles enter- 
ing, all or some of them, into every known 
substance, were supposed to be not neces- 
sarily capable of individual existence them- 
selves. ‘This was the view held by the fol- 
lowers of Aristotle. With the reaction 
against the domination of the scholiasts, 
other views began to be held. It was 
Boyle who first gave voice to these changed 
views in his ‘Sceptical Chemist’ (1661). 
He defined elements as “‘ certain primitive 
bodies, which, not being made of any other 
bodies, or of one another, are the ingre- 
SCIENCE. 275 
dients of which all those called perfectly 
mixed bodies are immediately compounded, 
and into which they are ultimately re- 
solved.’ He, however, did not believe him- 
self warranted, from the knowledge then 
possessed, in claiming the positive existence 
of such elements. 
But little attention was paid to the sub- 
ject by the subsequent chemists. The 
phlogistics were too much occupied with 
their theory of combustion, and none could 
see the bearing of this question and its im- 
portance to exact science. 
Macquer, in his ‘Dictionary of Chemis- 
try’ (1777), words his definition as follows: 
‘Those bodies are called elements which 
are so simple that they cannot by any 
known means be decomposed or even al- 
tered and which also enter as principles or 
constituent parts into the combination of 
other bodies.” To this he adds: ‘The 
bodies in which this simplicity has been 
observed are fire, air and the purest earth.” 
In all of this may be observed the resolu- 
tion of observed forms of matter into pri- 
mal principles following the dream of 
Lucretius and the early Epicurean philoso- 
phers, a dream abandoned by the atomic 
school following, though largely holding to 
the same definition. 
It was only when chemists began to real- 
ize that mere observation of properties, 
chiefly physical, was not sufficient that the 
subject began to clear up and lose its vague- 
ness. Black proved that certain substances 
were possessed of a constant and definite 
composition and fixed properties, unalter- 
able and hence simple bodies or elements. 
Lavoisier finally cleared the way for the 
work of the nineteenth century by his 
definition that ‘‘ an element is a substance 
from which no simpler body has yet been 
obtained ; a body in which no change causes 
a diminution of weight. Every substance 
is to be regarded as an element until it is 
proved to be otherwise.”” With this clear 
