During the Sessions of the American Association, the new Astronomical
Instruments of Dudley Observatory were described in detail by Dr. B. A.
GOULD, who is the Astronomer in charge. We condense his statements:--
The Meridian Circle and Transit instrument were ordered from
Pistor & Martins, the celebrated manufacturers of Berlin, by
whom the new instrument at Ann Arbor was made. A number of
improvements have been introduced in the Albany instruments, not
perhaps all absolutely new, but an eclectic combination of late
adaptations with new improvements. Dr. Gould made a distinction
of modern astronomical instruments into two classes, the English
and the German. The English is the massive type; the German,
light and airy. The English instrument is the instrument of the
engineer; the German, the instrument of the artist. In ordering
the instruments for the Albany Observatory, the Doctor preferred
the German type and discarded the heavier English. He instanced,
as a specimen of the latter, the new instrument at Greenwich,
recently erected under the superintendence of the Astronomer
Royal. That instrument registers observations in single seconds;
the Dudley instrument will register to tenths of seconds. That
has six or eight microscopes; this has four. That has a gas lamp,
by the light of which the graduations are read off; the Albany
instrument has no lamp, and the Doctor considered the lamp a
hazardous experiment, affecting the integrity of the experiment,
not only by its radiant heat but by the currents of heated air
which it produces. The diameter of the object-glass of the Albany
instrument is 7-1/2 French inches clear aperture, or 8 English
inches, and the length of the tube 8 feet. He would have
preferred an instrument in which the facilities of manipulation
would have been greater, but was hampered by one proviso, upon
which the Trustees of the institution insisted--that this should
be the biggest instrument of its kind; and the instruction was
obeyed. The glass was made by Chance, and ground by Pistor
himself. The eye-piece is fitted with two micrometers, for
vertical and horizontal observations. Another apparatus provides
for the detection and measurement of the flexure of the tube.
Much trouble was experienced in securing a good casting for the
steel axis of the instrument. Three were found imperfect under
the lathe, and the fourth was chosen; but even then the pivots
were made in separate pieces, which were set in very deeply and
welded. Dr. Gould said he had been requested by the gentlemen who
had this enterprise in charge to suggest, as a mark of respect to
a gentleman of Albany who was a munificent patron of Science,
that this instrument be known as the Olcott Meridian Circle.