The Bolivar bulletin. [volume] (Bolivar, Hardeman County, Tenn.) 1865-1888, 1877-08-02
The Great Lick Telescope.

Richard S. Floyd, one of the trustees
of the Lick Trust, has just returned from
an extended European tour. During his
absence he has talked with many scien-
tific men of this and other countries, but
almost invariably found them afraid to
commit themselves to an opinion as to
whether greater success can be obtained
with a rejecting or refracting telescope.
Prof. Newcombe, of the observatory in
Washington, after his visit to Europe to
look into this matter for Mr. Lick, re-
ported warmly in favor of a gigantic re-
tractor, and forwarded complete esti-
mates as to the cost. He has since changed
his opinion, however, and now recon-
meuds a silver on-glass reflector of about
seven feet diameter. Ross, Herschel's,
and other celebrated telescopes have
speeulum-metal reflectOrs, which have
until lately been considered the best.
Now the palm is claimed for an inven-
ton of Leon Foucault's, by which silver
in solution is deposited on glass. Fou-
cault made a reflector upon this system
about thirty-One and one-fifth inches in
diameter, and excellent work has been
accomplished with it. After his death,
a reflector upon this plan about four feet
in diameter was constructed for the OBJ
servatory. Owing to some not thor
oughly explained cause this has not
proved a success, and another of the same
dimensions is being cOnstru cted to re-
place it. Great interest is manifested IN
the result of this second experiment,
which cannot be proven for q year yet.
DR.. Higgins, the well known astronomer,
also favOfs large reflector, as it is better
for spectrOscopic analysis, his tavorite
study. 1t is natural that he should pre-
| fer a reflector, as he desires to have the
field of physical astronomy enlarged.
Theoretically a reflector of four feet in
diameter is about equal to a refractor of
twenty-siX inches. The Ross reflector is
six feet in diameter, emily fotr feet of
which are effective, and 50 far it has not
| been proven that more than four feet of
a reflector can be made effective. The
great trouble with the reflector is that it
is very sensitive to atmospheric changes,
while with the refTactOr the difficulty
lies in the secondary spectrum. The OBJ
| iect-glasS of the refractOr is composed of
| two glasses Joined, the outer being of
| crown glass, the inner of flint. Rays
passing through the crown glass are re-
| fracted, and entering the flint glass, are
| refraUted. The consequence is that per-
/ feet achrOmatism is impossible, and the
! difficulty of compensating these refrac-
lions increases with the size of the obiect-
glass. The largest refractor in the world
| IS that in the Washington observatory !;
it is twenty-six inches in diameter.
Mr.. Floyd said that after as careful an
examination as he could make, he is in
clined to believe that the best interests
| of the fund will be served, to have con-
| structed a larger re ractOr than any yet
made This ought not to cost, com plete,
more than $4,000. Then thete will be
a subsidiary reflector, about four feet in
| diameter, supplied with both silver-on-
| glass and speculum metal mirrors. Such
an instrument has been offered, or rather
| parties have agreed to construct one, for
about $4,000. Tell, of Paris, will under
take to make crown and flint glass discs
for the object glasses of a forty-inch re-
tractor for $50, 00-stipulating that he
shall he allowed two years for their com
struction. After they have lett his
hands the Optician will reduife about
three years more to figure these discs
| mathematicallY,