The phenomena at present known in connection with these sciences are so analogous
as to render it necessary for them to be studied in conjunction. Some of the properties of
LIGHT, with reference to its natural effects, are discussed under that article, and should first
be examined. The history of OPTICS, combined with the Introduction, exhibits a com-
plete view of the progress of that science; and the articles MICROSCOPE, MICROMETER,
and TELESCOPE, illustrate the present state of knowledge with reference to the construction
of those optical instruments. The theory of the BURNING-GLASS and BURNING-MIRROR
will be best understood by examining those articles in connection with REFRACTION and
REFLECTION. The RAINBOW and POLARIZATION of LIGHT, which are usually found difficult
subjects to comprehend, may now be understood.

Electricity and magnetism are intimately connected with the previous subjects. After
consulting the general articles ELECTRICITY, GALVANISM, and MAGNETISM, their connection.
will be further illustrated under ELECTRO-MAGNETISM, and SPECTRUM. The best forms of
the COMPASS, and mode of constructing Professor Barlow's improved apparatus, will be found
under that article and MAGNETISM.

THE study of this branch of science may be best commenced with the articles NEWTONIAN
PHILOSOPHY and ATTRACTION. The history of ASTRONOMY should be followed by an
acquaintance with the sizes and relative situations of the planetary bodies, and their satel-
lites taken in detail; the phenomena of eclipses, and the causes of the tides, may also then
be readily understood. The SEASONS are beautifully illustrated by Mr. Christie's tellu~

rium, described under that article, and a knowledge of practical astronomy may be best ac-
quired by a reference to the various instruments, as they occur in the work.

Equinoctial points

Planetary Years
Pleiades

Arctic

Arctophylax

Bootes
Bull

Firmament

Pollex

Fixed Stars

Arcturus

Arctus

Argetenar

Argo

Argument

Capricorn

Globe

Pollux

Precession of the Equi-

noxes

Quadrant

Quadrature

Repeating Circle

Sagittarius

Satellites

ANATOMY, MEDICINE, AND CHEMISTRY..

The history of these subjects, as well as physiology, pathology, &c., is given in the
Introduction to this work; and our acquaintance with the structure of the human body
must evidently be commenced with the articles ANATOMY, PHYSIOLOGY, MUSCLES, and
NERVES. The study of the ATOMIC THEORY is an important part of Chemistry, and the
student in this science will do well to make himself acquainted with the phenomena of light,
heat, and electricity, preparatory to an examination of ponderable matter. OXYGEN, Chlo-
RINE, and IODINE, will next come under his consideration, to be followed by the simple
acidifiable and inflammable substances. The metals, as well as the bodies which compose

the various animal and vegetable substances, will be found interspersed through the mis-
cellaneous articles of the work.