Note (return) — NOTES OF A READER.

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 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."