combination."--Bergman.

"Chemistry is that science which treats of those events or changes, in
natural bodies, which are not accompanied by sensible motions."--Dr.
Thompson.

"Chemistry is a science by which we become acquainted with the intimate
and reciprocal action of all the bodies in nature upon each
other."--Fourcroy.

The four preceding definitions are quoted by Mr. Parkes, in his
_Chemical Catechism_.

Dr. Johnson (from Arbuthnot) defines "chymistry" as "philosophy by
fire."

Mr. Brande says, "It is the object of chemistry to investigate all
changes in the constitution of matter, whether effected by heat,
mixture, or other means."--_Manual_, 3rd edit. 1830.

Dr. Ure says, "Chemistry may be defined the science which investigates
the composition of material substances, and the permanent changes of
constitution which their mutual actions produce."--_Dictionary_,
edit. 1830.

Sir Humphry Davy, in his posthumous work,[6] says, "There is nothing
more difficult than a good definition of chemistry; for it is scarcely
possible to express, in a few words, the abstracted view of an infinite
variety of facts. Dr. Black has defined chemistry to be that science
which treats of the changes produced in bodies by motions of their