On the evening of the 4th of May, the committee met, by appointment,
in an open lot south of the Pennsylvania Hospital, for the purpose of
testing the performance of the telescopes, which had previously been
tried by some of the members of the committee, and by other gentlemen,
on the evening of the 2d. The result of the examination was highly
creditable to Mr. Holcomb, and cannot fail to gratify all who have at
heart the advancement of astronomical science in this country.
The instruments, with powers varying from 50 to 600 in the smaller,
and to 900 in the larger, gave satisfactory views of the moon with a
sufficiency of light.
Mr. Holcomb’s ability to manufacture telescopes which should bear a
comparison, on favourable terms, with the best four and five feet
achromatics now in the country, having been established by the report
of the committee in May, 1834, their attention was chiefly directed to
ascertaining the degree of perfection to which he has attained in his
art, by his persevering efforts during the past year. Accordingly, the
remarks which follow are made with reference to the larger telescope, of
about ten feet focal length, eight inches aperture, and with a positive
eye-piece, giving a power of about 900, and the surface of the field of
view nearly twice as great as that of a Gregorian, and one-third greater
than that of an achromatic telescope, under similar circumstances.
The view of the moon with its rugged surface, its ridges of mountains,
and the endless variety of indentations on its surface, was interesting
beyond description, and exceeded any thing of the kind the committee have
ever witnessed.
Saturn’s ring, though not in a favourable position, was seen manifestly
double, for the first time in this country, as far as the information of
the committee extends.
The companion of Polaris appeared as a star of the fourth or fifth
magnitude, to the unassisted eye.
The double stars, Castor, μ Draconis, 4 and 5 ε Lyræ, and 44 Bootes, were
distinctly separated, and the dark space between them made evident. The
last mentioned, consisting of two stars of the fifth magnitude, distant
3″ made a fine appearance; they were soft, and well defined, and there
were no scattering rays of light, as was the case with Castor, in both
instruments.
A class of closer doubles stars, of which 6 Coronæ, distant 1″.2., and
ζ Bootes, distant 1″.4., may serve as examples, was acknowledged by
the artist, last year, to be too difficult for his telescope. This has
furnished a stimulus for his exertions, and the complete division of the
latter, as witnessed by the committee on the present occasion, has been
the reward of his disinterested labours. The discs of the two stars in
ζ Bootes appeared to be tangent to each other. The committee have no
evidence that the same has been effected by any other telescope in the
country.
For the purpose of finding the limit to the power of Mr. Holcomb’s
telescope, the committee called his attention to a class of still closer
stars; among them were mentioned, ζ Cancri, μ2 Bootes, ῎ Coronæ, 36
Andromedæ, and ε Arietis, the last of which is only divisible by two
telescopes now in use, viz.: the Dorpat telescope, and the twenty
foot reflector of Sir John Herschel. These stars, distant from 0″.6.
to 1″.0., are made to appear with their discs tangent to each other in
those celebrated instruments, as appears by their notes appended to the
observations contained in their printed catalogues. It is almost needless
to add, that Mr. Holcomb acknowledged these stars to be too difficult for
any telescopes he has yet made.
It may seem presumptuous to compare the small instrument of Holcomb with
the chefs d’oeuvre of British and German genius; but, thanks to the
admirable labours of the Herschels, of Struve, and of South, observers
are enabled, through their printed catalogues, to compare together the
optical capacities of their telescopes in distant regions. Accordingly
it appears from an examination of these catalogues, and of Holcomb’s
instruments, that what the best telescopes in Europe can do upon stars
distant 0″.6., can be done upon stars distant 1″.4., by instruments which
are the work of an unassisted, and almost neglected, American optician.
Judging from the progress made in his art, by Mr. Holcomb, during the
past year, the committee look forward, with confident expectation, to the
not far distant period, when, should his health be spared, the country
will be in possession of a twenty feet reflector, of native workmanship,
rivalling the best European instruments, and that, too, without the
patronage of any corporate institution, should all of them be willing to
waive the opportunity of sharing with him the merit of such an enterprise.
The committee have been led to enlarge upon this subject, from a
knowledge that one of our national institutions has, within a few
years, imported into the country, at an expense of $2,500, a telescope
which, though excellent in its kind, is inferior to that exhibited by
Mr. Holcomb, which was made and mounted to order for an individual in
Georgia, at less than the eighth part of the above mentioned sum. It is
not probable that a twenty foot instrument from Mr. Holcomb, would cost
eight times as much as one of the length of ten feet.
The mode of mounting the instrument appears to be original, and nothing
can exceed it in simplicity, or steadiness. Indeed, with a power of
900, no inconvenience was perceived from resting with one hand on the
frame, and another on the tube, although the same could not be done
with the mounting used by Mr. Holcomb last year, or with that of common
achromatics with a power of 200, without serious inconvenience.
In conclusion, the committee beg leave to recommend Mr. Holcomb to the
Board of Managers of the Franklin Institute, as a candidate for a premium
and medal from the Scott’s legacy fund, for his new mode of mounting
reflecting telescopes.
By order of the committee.
WILLIAM HAMILTON, _Actuary_.
_May 14th, 1835._