The Osceola times., 1877-08-04
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-
tifc 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 retracting telescope.
Prot. Newcombe, of the observatory in
Washington, alter his visit to Europe to
look into this matter for Mr.. Lick, re-
ported warmly in favor of gigantic re.
tractor, and forwarded complete esti-
mates as to the cost. Hehas since changed
his opinion, however, and now recon-
mcnds a silver.on-glass reflector of about
seven feet diameter. Ross, HerschePs,
and other celebrated telescopes have
speculum-metal rchectors, 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 depc sited on glass. Fou.
cault made reflector upon this system
about thirty one and one.fitth inches in
diameter, aad excellent work has been
accomplished with it. Aftfr his death,
a reflector upon this plan about four feet
in diameter was constructed for the OBJ
servatory. Owing to some not thor
oushly explained cause this has not
proved success, and 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 he proven for a year yet.
DR.. Higgins, the well known astronomer,
also iavors a large reflector, az it is better
for spectroscopic analysis, his iavorite
study. 1t is natural that he should pre-.
fer reflector, as he desires to have the
field OF physical astronomy enlarged.
Theoretically reflector of four feet in
diameter is about equal to reiractor 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 tie 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, the inner OF flint. Rays
passing through the crown glass are re-
fracted, and entering the flint glass, are
refracted. The consequence is that per.
feet achromstism is impossible, and the
difficulty OF compensating these refrac-
tions increases with the size OF the object.
glass. The largest refractor in the world
is that in the Washington observatory /;
il is twenty-six inches in diameter.
MIR. 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 larger re ractor than any yet
made. This ought not to cost, complete,
more than $l50.00o. Then there will be
subsidiary reflector, about four feet in
diameter, supplied with both silver-on.
glass aud 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 Dies
Tor the object glasses OF forty-inch re-
tractor for 500, ,000-stipulating that he
shall Re allowed two years for their con.
struction. After they have LETT his
hands the optic;an will require about
three years more to figure these discs
matbematically.