ience which treats of the changes produced in bodies by motions of
their ultimate particles or atoms, but this definition is hypothetical,
for the ultimate particles or atoms are mere creations of the
imagination. I will give you a definition, which will have the merit of
novelty and which is probably general in its application. Chemistry
relates to those operations by which the intimate nature of bodies is
changed, or by which they acquire new properties. This definition will
not only apply to the effects of mixture, but to the phenomena of
electricity, and, in short, to all the changes which do not merely depend
upon the motion or division of masses of matter. However difficult it
may have been to have given you a definition of chemistry, it is still
more difficult to give you a detail of all the qualities necessary for a
chemical philosopher. I will not name as many as Athenaeus has named for
a cook, who, he says, ought to be a mathematician, a theoretical
musician, a natural philosopher, a natural historian, &c., though you had
a disposition just now to make chemistry merely subservient to the uses
of the kitchen. But I will seriously mention some of the studies
fundamental to the higher departments of this science; a man may be a
good practical chemist perhaps without possessing them, but he never can
become a great chemical philosopher. The person who wishes to understand
the higher departments of chemistry, or to pursue them in their most
interesting relations to the economy of Nature, ought to be well-grounded
in elementary mathematics; he will oftener have to refer to arithmetic
than algebra, and to algebra than to geometry. But all these sciences
lend their aid to chemistry; arithmetic, in determining the proportions
of analytical results and the relative weights of the elements of bodies;
algebra, in ascertaining the laws of the pressure of elastic fluids, the
force of vapour as dependent upon temperature, and the effects of masses
and surfaces on the communication and radiation of heat; the applications
of geometry are principally limited to the determination of the
crystalline forms of bodies, which constitute the most important type of
their nature, and often offer useful hints for analytical researches
respecting their composition. The first principles of natural philosophy
or general physics ought not to be entirely unknown to the chemist. As
the most active agents are fluids, elastic fluids, heat