Quarterly Scientific Intelligence [pp. 350-356]

Quarterly Scientific Intelligence.
tiful way of making wet preparations for the microscope. The
preserving cell, when completed, is composed of three pieces of
plate-glass, cemented together, the middle one having a circular
hole cut out of its central portion for the reception of the spe.
cimen and preserving fluid. This hole may be conveniently cut
by means of a copper tube, properly set in a lathe, and fine
emery or sand.. The middle plate should be of such thickness
that the preparation may be slightly pressed between the other
two, so as to hold it in its place. The plates must be made
perfectly clean, by means of sulphuric acid and potash, and
dried with a muslin handkerchief. The middle plate and bottom are first cemented together. The cement which Dr.
Goadby prefers is a marine glue, suggested by Dr. P. B. Goddard, of Philadelphia. It consists of caoutchouc dissolved in
chloroform, by the aid of a gentle heat, to the consistence of
a mucilaginous paste, with the addition of carefully selected
tears of gum mastic until the mixture becomes sufficiently fluid
to use with a brush. The cover should be of thin plate glass,
cut a little smaller than the other plates.
The preserving fluid should be made to come into close
contact with the sides of the preserving cell by means of
a brush, or the preparation will be injured by the gradual
appearance of small bubbles of air. The cell being completely filled with the fluid, and having as much poured upon
it as can be made to remain there, is to be covered with
the plate designed for that purpose, which should be previously wetted by rubbing it with a brush. The fluid is then
to be carefully wiped from around the edges of the cover,
and the cover cemented by successive coats of the cement
before mentioned, applied. around its edge.
American Optical Instruments.-Mr. Charles A. Spencer of
Cannasota, New York, has constructed a microscope-object.glass in accordance with his new formula, which seems to indicate a decided improvement in the art. He has obtained an
angle of aperture of 1741 degrees-considerably greater than
was deemed possible up to the time of his discovery. The
instrument resolves the markings of test objects in the most
satisfactory manner.
Mr. John Lyman of Lenox, Massachusetts, has recently constructed a reflecting telescope, of 16 feet focus, and having an
aperture of 91 inches in the clear. The arrangement for
observation is that of Herschell and Lord Rosse. The remarkably accurate figure of the speculum is evinced by the clearness
with which it resolves the double stars, in instances when they
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