The Hickman courier. [volume] (Hickman, Ky.) 1859-current, 1877-08-10

Richard s Floyd, one Of the trustees
of the Lick Trust. has just returned from
an extended European tour. During bis
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 reiracting 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 3 gigantic 70
tractor, and forwarded complete esti-
mates rs to the cost. He hiss since changed
his opinion, however, and now recon-
mends Silver-on-glass reflector of about
seven feet diameter. Ross, Herscheis,
and other celebrated telescopes have
speculum-metal refect0rs, 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. aled 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 solae not thor
oushly explained cause this has not
proved a success, and auotf er OF the same
Dimensions IS being constructed TO re-
place it. Great interest Is manifested III
the result Of this second experiment,
which cannot be proven t1r year vet
Dr. Higgins, the well-knOyn astronomer,
also favors a large reflector, as It Is better
for spectroscopic analysis, has iayorIie
study. 1t is natural that he should pre-
fer a reflector, rs he desires to have the
field of physical astronomy enlarged.
Theoretically reflector OF four feet in
diameter is about equal to retractor of
twenty-six inches. The Ross reflector is
six feet in diameter, only four feet Of
which are effective, and so far 1t 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-gIass 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
difficulty of compromising these refrac-
tons 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 larger re ractor than any yet
made This ought not to cost, complete,
more than $4,000. Then there 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 $40, 900. Tell, of Psris, will under
take to make crown and flint glass discs
for the object glasses of q forty-inch re-
tractor for $50, 000-stipulating that he
shall be allowed two years for their con-
struction. After they have lett his
hands the optician viii require about
three years more to figure these discs
mathematically.