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