The daily union. [volume] (Washington [D.C.]) 1845-1857, 1847-11-23

States whence public vessels might be suitably sup
cation The site Of the observatory is beautiful one,
commanding fine view Of Georgetown, Washington,
Alexandra, Fort Washington Opposite Mount Vernon
the city 1t occupies University Square, plot OF ground
comprising seventeen acres, the suburbs of Washing
ton the left bank OF the Potomac, and about hun
BY General Washington for the site OF great university
The observatory, however is naval institution, con-
Quoted entirely BY naval officers, under the direction Of
The law requires that the superintendent or director shall
DC either lieutenant commander or captain IN the navy
OF the United States
The main building is of brick, SO feet square, and
two stories in height, surmounted by revolving dome
Of 90 feet diameter in the clear. in which is placed the
Ms. es tn e
main buildings as observing roOms wings extending
IS feet to the east and west and projection Of SO feet
furnished with set Of excellent astronomical nstru
ments, consstng1 OF the large refractor, the dome
already alluded 10, Of l4i feet focal length with OBJ
ally mounted, and furnished with clock-work. 2. A
transit instrument of IL feet focal length and SO
inches clear aperture made BY Ertel and Son. MUNICH
and mounted on the meridian in the west wing, where
there is also clock with mercuria pendulum made
by Parkinson Frodsham. In the east wing s-3. A
ing 3s inches aperture with focal distance OF 40
feet This instrument is provided with 80 inch circle
divided into OF 81 and read to seconds and tenths by
four microscopes; few feet from this, in the same
room, stands 4 The elegant mural circle, English in
srument, by Troughton Sims, of feet diameter, d.
vded into Of s. value and furnished with six read
ing microscopes with which subdivisions of the circle
obtained in seconds and parts OF seconds The OBJ
ect glass Of the telescopes Of the same size with that
81 the meridian CIRCLE Tl,n focal Length o. feet the ne
Charles Frodsham
In the south wing first apartment, s. The fine transit
instrument made by Piston Martins, of Berlin, for the
prime vertical 1t is mounted at end OF its axis, and
outside Of its supports It is reversed from to the
other side of these twice during every observations and
its system of counepoises and the reversing apparatus
that child can lift it from it's Us, and replace it
in them in less than one minute. The focal length OF
this telescope is 65 feet with clear aperture of 40
inches; the clock has grdiron pendulum, and is OF
Charles Frodshams make.
The observations made with instruments thus mount
ed, are among the most accurate known in astronomy;
and those now making in Washington have not been
surpassed by any at the oldest observaiores in Europe
It is believed that there is not single made during
the whole of the last year, which differs much as /"
from the mean OF all the others upon the star
catalogue OF all the stars within the reach of this nstr
men has been already commenced at the national obser
vatory, which, when completed will be regarded by
ronomers as standard work. and, perhaps the most
accurate catalogue that has appeared careful
vision Of this catalogue in after years. will probably lead
to highly valuable and interesting results.
But wonderful as the degree Of accuracy in the re-
suits obtained from this instrument, Lieut. Maury has
discovered imperectons in it, which he has sought
correct by another For this purpose he urnished Messrs
Erel Son with plans and drawings of improved in
sument which has been lately received at the Observa
tory, and which understand those skillfu makers
pronounce to be the most complete astronomical nsu
ment that they have ever made. It intended to be
mounted temporarily in the prime vertical in the other
apartment Of the south wing. But after it has been APP
piled in this direction to the investigation Of the several
problems which connected with it's position east and
west i is then to be turned permanently the meridian
where il will be used for observations upon atmospherica
reirectiops paraax &C. and for the purpose Of deter
Ps I'll se epsss: q 6s meridian transit
srument procured this country for the purpose Of
investigating the subject Of amospherca refractions
Lieut. Maury has called it the ''Refracton Circle"
though its objects and by confined to
this subject alone For instance in the meridian It is
both mural and transit instrument and by of its
facilities for reversal, zenith sector; also, it is well
adapted for measuring the difference in zenith distance
between north and south stars In the prime vertical it
becomes improved zenith sector, and takes the place
Of the prime vertical transit instrument with all the ad
vanages superadded Of an altitude instrument in that d.
rection.
We have not been able to obtain accurate measure
ment OF all parts of this instrument The telescope is 81
feet long, with clear aperture of inches. 1t is sup
ported in the middle of the axis betueen piers; has
two 4eet circles, each end of the axis divided on
reading microscopes The telescope has two micrem
eters, one moving in azmuth the other in altitude tits
80 contrved that the wires, and not the field, um
mated and every eyepiece even of the highest powers
just as is used and without alteration of any kind be-
comes colimadng eye-pece by simply turning the tcle
down basin q mercury At one end Of the
in the focus of lens placed at the other end Of the axis
Upon the pro0ngation of this axial line at either end
and attached to the same piers which support the tele
scope, placed two colmators which ingenously
conrved to stand in the place both of the srdng level
and meridian marks and which are to be used for deter
mining the level of the instrument the figure of the axis
and the eccenrcity of the pvots. There is further
provision for detecting the slightest changes in the deva
ton OF the levc! of the axis from normal state
count OF unequal expansion of the supporting PIERS which
of granite This consists Of another beautiful con
vance, by of couple Of nvarable rods or rods of
we-deermned expansibility, which inserted vert
cay through the piers; and which, by turning mirror,
show the mnutes alterations which take place from
this source In the level or inclination of the axis of the
instrument. Thus the imperfecons of the spirit-leve
with but part OF the inconvenience of strdng level
10 reverse with the instrument, are secured.
Approaching the advantages which these fine nstru
with the determination OF so employing them that their
results, while they should be the most useful would at
the time most rebound to the credit of the observa
tory and the navy and to the honor of the country The
national observatory being naval institution, its first OBJ
ec and duty would seem to be to undertake those obse
vations which most Immediately connected with nav
cation, and the results Of which might afford the data
requisite for calculating American nautical almanac
Accordingly the naval astronomer at commenced
the and moon, the planets and list of flndamen-
tai stars, comprising those of the greatest magnudes and
OF the most favorable POSITIONS 10 be used the stand
ard stars in the almanac But these did not give full EN-
pioyment either to the instruments, the observers. or
the computers Accordingly, after having adjusted his
pians Lieut. Maury took early opportunity, in 1s45
OF making them known to the Secretary of the Navy
ana OF ootanng IRON him authority to undertake obser-
vations for most extensive catalogue of stars This
nnrk WI rnYnnt nd