nce. The discussion of this subject forms,
the branch of optics, touching physical science on the one side, the
most refined, and the highest range of mathematics on the other.
Rittenhouse first suggested the true explanation of the experiment, of
the apparent conversion of a cameo into an intaglio, when viewed through
a compound microscope, and anticipated many years Brewster's theory.
Hopkinson wrote well on the experiment made by looking at a street lamp
through a slight texture of silk. Joscelyn, of New York, investigated
the causes of the irradiation manifested by luminous bodies, as for
instance the stars. Of late, photographic experiments have occupied much
attention, and Draper has advanced the bold idea, supported by
experiment, that the agent in the so-called photography, is not light,
nor heat, but an agent differing from any other known principle. Henry
has investigated the luminous emanation from lime, calcined with
sulphur, and certain other substances, and finds that it differs much
from light in some of its qualities.

Astronomy is the most ancient and highest branch of physics. One of our
earliest and greatest efforts in this branch was the invention of the
mariner's quadrant, by Godfrey, a glazier of Philadelphia. The transit
of Venus, in the last century, called forth the researches of
Rittenhouse, Owen, Biddle, and President Smith, near Philadelphia, and
of Winthrop, at Boston. Two orreries were made by Rittenhouse, as also a
machine for predicting eclipses. Most useful observations, connected
with the solar eclipses, from 1832 to 1840, have been made by Paine, of
Boston. We have now well-supplied observatories at West Point,
Washington, Cambridge, Philadelphia, Hudson, Ohio, and Tuskaloosa,
Alabama; and the valuable labors of Loomis, Bartlett, Gillis, Bond,
Pierce, Walker, and Kendall are well known. Mr. Adams, so distinguished
in this branch and that of weights and measures, laid last year the
corner stone of an observatory at Cincinnati, where will soon be one of
the largest and most powerful telescopes in the world. Most interesting
observations as to the great comet of 1843 were made by Alexander,
Anderson, Bartlett, Kendall, Pierce, Walker, Downes, and Loomis, and
valuable astronomical instruments have been constructed by Amasa
Holcomb, of Massachusetts, and Wm. J. Young, of Philadelphia.

It is difficult to class the brilliant meteors of November the 13th,
1833. If such meteors are periodic,