The Ouachita telegraph. [volume] (Monroe, La.) 1865-1889, 1881-04-08
AsTKIuMPH OF IRISH SKILL.

AsTRrpMrH OF IRISH SKILL.
The Largest relescope in the world.
The most powerful refracting tele-
scope ever manufactured in any coun
try has just been completed by Mr.. |
Howard Grub, Fellow of the Royal
Astronomical Society of London, at
his extensive works on the Rathmines
road, Dublin. This enormous and
most beautiful instrument is known as
the great Vienna Refractor, and will
in short time, be permanently loca-
ted in the Imperial and Royal Obser-
vatory. TWAS ordered by the Aus
trian Government in 1875, and the
equatorial aud mechanical parts were
completed in Dublin in the Summer
of 1878, but such was the exceeding
difficulty of obtaining perfect discs OIL
optical glass of the proper size, that al
though Messrs. Fiel, of Paris, who I'M
dertook to supply the material for the
glass, sent over several discs to Dublin
during the past four years the perfect
ones were not obtained till October,
1879. These were as expeditiousIy as
possible worked into the objective at
Mr.. Grubb's manufactory, and he was
enabled to report the instrument COM
piete in December of last year. Thus
the object glass was completed in less
than half the time stipulated for it in
the contract. 1t follows that the long
period during which the work was in
hand was attributable altogether to the
slowness of the French firm, who took
four years to supply What they UNDER
| took to do in one. Some idea of the
extent softhis work, and of the risk at
ltendant on it's manipulation may be
gathered from the fact that the rou oh
glass as obtained from the Partisan
manufacturers cost eI20O (e6Oo each
disc and the finished object glass is
now valued at e400O, quite indepen-
dent of its equatorial mounting. The
| tube alone, it may be mentioned,
weighs seven tons, but it can be moved
! by a child.
1 Several refinementS and novelties
have been introduced by Mr. Grub
| into this wonderful Vienna Equatorial
| of 81 inch aperture.
The largest telescope in England is
that erected some ten years ago at
| Newcastle on Lyme, which is % inches
| in aperture. Americans improved on
this some years since by manufacturing
one with 26 inch aperture, the in
strument being at present in the
| Naval Observatory at Washington /;
but the credit of the largest refracting
| telescope yet made is now due to Ire
land, Mr.. Grub having just produced
1 a 81 inch aperture. The power of q
telescope depends simply and solely on
the aperture Of the object glass, and
from this it will be apparent that the
,fv.r hi
. stands complete in the observatory al
Rathmines is the most powerful re
i fracting telescope in the world. Lord
Roses and the great Melbourne tele-
lcopes, with its mirror four feet in dia
I meter. constructed By Mr.. Grubb for
i the Government of Victoria, New
South Wales, are, no doubt, larger in
1 diameter than the Vienna, but those
are rejecting telescopes, and no com
! parison can consequently be instituted
i between them and refraciors. Tt is
i generally assumed that refracting tele-
scopes should bears magnifying power
lof 100 for every inch in diameter and
according to- this acceptation, power
of 2.7OO should be disable with the
Vienna telescope, or, in other words
an object 300 miles away should
viewed through this instrument, ap
pear as an object only one mile away
Looked at through the Vienna, under
perfect atmospheric conditions, the
moon, which is distant from the eartf
100000 miles, should appear ut les:
/. than 100 miles. Such atmospheric con
ditions as would secure this are, how
ever, practically impossible in our lati
, tudes whatever they might be if tho
telescope were placed on the top o.
) the Himalayas. The astronomers a
Washington tell us that GOO diameter:
on the 26 inch glass is themost gen e
{ rally useful.
THE YORKTOWN CENTENNIAL.