The star of Pascagoula. [volume] (Pascagoula, Miss.) 1873-1878, 1877-08-03
The Great Lick Telescope.

Richard S. Floyd, one of the trustees
of the Lick Trust, has just returned from
an extended European tour. During hi'
absence he has talked with many scien'
tifc men of this and other countries, but
almost invariably found them afraid to
commit themselves to an opinion as to
whether q 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-
mends a silv~er.on-glass reflector of about
seven feet diameter. Ross, Herschel's,
and other celebrated telescopes have
speculum-metal rehectors, 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-tifth inches in
diameter, ard 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, aud another of the same
dimensions is being constructed to re-
place it. Great interest is manifested in
the result OF this second experiment,
which cannot be proven for a year yet.
DR.. Higgins, the well known astronomer,
also tavors a large reflector, as it is better
fer spectroscopic analysis, his tavorite
study. 1t is natural that he should pre-
Ter 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, only four feet of
which are effective, and so 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 refractor 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, lne lHHtI VI HlHb' nays
passing through the crown glass are re-
fracted, and entering the flint glass, are
refracted. The consequence is that per
feet achromatism is impossible, and the
difficulty of compromising these refrac-
tions increases with the size of the object
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, complete,
more than $50, 002. Then there will be
a subsidiary reflector, about four feet in
diameter, supplied with both silver-on-
glass and speculum metal mirrors. Such
instrument has been offered, or rather
parties have agreed to construct one, for
about $50, 900. Tell, of Paris, will under
take to make crown and flint glass discs J
for the object glasses of a forty-inch re-
tractor for $40, 000-stipulating that he
shall he allowed two years for their con-
struction. After they have left his
hands the opticisn will require about
three years more to figure these discs
mechanically.