The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1874-07-14

ully adapted for dividing double stars, ana under
the management OF Struve achieved a very great
than than any other Instrument NJ run IN Europe.
Greenwich, OF course has some tine telescopes,
altnough IL Is now more prominent rs meteoro-
logical and surveying bureau ana as the neauquar-
ters for longitudes and ATTITUDES all the world over
than as an observatory OF stellar phenomena
In Paris the telescopes IN use are mostly renee
tors OF glass; sllvered on the 'front.' surface alter
Foucaut's method. Although Merz, az Munlch:
makes so many glasses for all parts on Tue wop ,
Germany has none OF the monster telescopes IKE
Lord ROsse's.
at ParsonstOwn, Louth, Ireland, when mas been
probably every day pointed AZ the comet was
completed some twenty-slx years ago. AZ 10 q
ieet and a focal length OF dty-three feet, two
specula, one weighing three and hall and the
other tour tons BY resting the ins1fumen. upon
that they distributed the pressure equally, a COM
plete equilibrium OF all the parts OF the spectrum
was obtained subsequently twenty-seven TIL
angles, each with ball at the angles were suo-
stituted. so that the spectrum rolls freely on
eighty one balls. The telescope tube rests upon q
JOINT OF cast iron, which is supported upon stone
work, and Can be moved with the greatest ease.
The ordinary far mcrometer with coarse threads
is generally USED, and these threads, from the
power or the rejecting surface below, are OF daZ-
zing orilllancy even In the most profound dark.
ness Lassel's telescope Ia Malta, constructed
after Newtonian principles, Ia very large one,
beng Jour ieet in diameter.
THE GREAT MELBOURNE TELESCOPE
manufactured by Mr.. Grub. OF Dublin. is OF the
rejecting order. The reflector IL OF metal, al
though the new siivered glass OF Foucault is pre-
ferred BY many astronomers, as being better
adapted for these Instruments. II is claimed by
these scientists that metal renects less light and
that the me tai renectors cannot be so easily re-
pared when they have once lost their polish. Re-
polishing OF these refectOrs Is really nothing more
nor less than renguring, which Is a very eXpen-
slVe process. Resilverlng glass mirror, however,
Is attended by comparatively slight expense and
does not require extraordinary talent. The point
OF suspension rs near the MIRROR and In front or
this point the telescope stretches forward to about
thirty feet OF open lattice work, made OF bands Of
Al .Gfi ar ha 10 an ina
plan, with the eye-piece as in the Gregorians at
the bottom, and exceedingly convenient Tor use.
SOUTH AMERICAN ASTRONOMY.
few words about observatory in South
America. At Cordova In the Argentine Republic,
DR.. Gould, OF Cambridge, Mass. established an
observatory where two valuable instruments are
used, RepsOd meridian circle OF fity-jOur inches
local length and four and half IN aperture and
eleven-incn object glass formerly the property of
DR.. Rutherford, OF this city.
We can only casually mention few more OF the
leading acbromatlc telescopes. AT the Royal OBJ
servatory In Munich there Is one OF liz inches
aperture and 1872 focal length, al Paris and Dublin
there Is one Of l2.4 aperture and 206 focal length.
and there are others in almost every capital OF
Europe and in Madras, Cape Town and other cities.
The subject is SO vast that 1t would be Impossible
to give in the limits OF a newspaper article more
than brief outline OF its salient points. 1t may
be Of interest, however to know
HOW THESE GREAT TELESCOPES ARE Used
in observations like that OF the comet or course,
ObservatOries differ in this respect but the folio
ing, which is authentic, will give an idea OF the
method generally in vogue The astronomer sits
upon an easy chair, with movable back. II the
object ne seeks Is nigh in the heavens this chair
back is lowered Till its occupant almost lies down.
Ii the star Is lower the char back Is raised IN pro-
portion. Across the eye-plece OF the telescope are
field Of view II his seat requires change the least
motion arranges 1t to his satisfaction for rests
upon railway of Its own. AS the star pa sses the
wires he records II on the chronograph. An ex-
pert observer will not commit an error in this
mental calculation exceeding the tenth part OF q
second, or the SIX hundreth part OF minute.
Stars not very near the sun may be seen in broad
daylght but at night 1t is necessary TO direct
ray OF light from a lamp TO enighten the
field of the telescope 80 as to permit the spider
lines to be seen running across the brighter
ground on which the expected star Is to be visible
This Is the account given by an astronomer who
watched the -gazers At the Green wich observa
tory.