emporary
literature. Few of them, however, are first-rate. The most original
portion consists of the Astronomical Occurrences, which extend to 150
pages.

* * * * *

POPULAR CHEMISTRY.

Such is the title of the fifth part or portion of _Knowledge for the
People: or, the Plain Why and Because:_ containing Attraction or
Affinity--Crystallization--Heat--Electricity--Light and
Flame--Combustion--Charcoal--Gunpowder and Volcanic Fire. We quote a few
articles from most of the heads:--

Why is the science of chemistry so named?

Because of its origin from the Arabic, in which language it signifies
"the knowledge of the composition of bodies."

The following definitions of chemistry have been given by some of our
best writers:--

"Chemistry is the study of the effects of heat and mixture, with the
view of discovering their general and subordinate laws, and of improving
the useful arts."--Dr. Black.

"Chemistry is that science which examines the constituent parts of
bodies, with reference to their nature, proportions, and method of
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
ultimate particles or atoms; but this definition is hypothetical; for
the ultimate particles or atoms are mere creations of th