The Washington union. [volume] (City of Washington [D.C.]) 1857-1859, 1858-09-12

THE NATIONAL OBSERVATORY.


This building is situated about mile west from the
Executive Mansion upon elevated site and commands
beautifl view of tho Potomac river and of the cities
Of Washington and Georgetown. 1t is under the direc
tion of Lieut. NJ. + Maury, who has able corps Of
astronomers and assistants and it has attained reputa
ton equal If not superior TO that Of many of the older
obseryaores whose merits acknowledged throughout
the civilized world. At every day ball is dropped
from flag staff which surmountS the dome, similar to
the one at Greenwich which enables naygators and 9th
es TO regulate their time to second As matter OF
general interest," will endeayor to give brief descnp
ton of this establishment.
This was originally designed and used for hydro
graphical ofoe and for long time the idea of having
National Observatory laughed at by politicians both
IN aud out Of Congress The business of the photograph
ica department. such the preparation of wind and
current charts from the abstracts of hundreds and thou
sands OF log books the regulation of chronometer &c.
Ii still regarded the primary object of the institution
and the astronomical department merely secondary
but gradually the importance of national astronomical
observatory has presented itself with increasing promi
nence before the minds Of statesmen and appropra
tons have been made by Congress from time to time to
procure Instruments Of various kinds and to furnish the
building with all the facilities necessary for the most del
icate and accurate astronomical observations.
In the west wing of the building situated the tran
sit instrument under slit twenty inches wide extend
ing entirely the roof and down the wall to with
in four five feet of the floor each side Inc wing
like tho other portions Of the building is of brick paint
ed cream color the outside The inside of the wing,
well the other observing rooms is plastered and
both the walls and the ceilings painted sky blue. The
floors Of all the observing are covered with oil
CLOTH and swept but the dust is removed with
hawet swab. The roof is coppeed and the trap doors
lined with green baize The transit instrument is
seven-foot achromac, with clear aperture of 5.3
inches, and made by Ertel Son. of Munich 1t is
mounted on two granite piers, each solid block, let
down below the floor for foot two, and firmly i'm
beided into stone foundation eight ten feet deep and
ten feet long by six feet wide the whole completely iso
lated from the building The piers feet high
and midway between them, running north and SOUTH is
the artificial horizon granite slab ten feet long, by
nineteen inches deep and thirteen inches broad This
rests firmly the foundation which supports the nstru-
men and like the PIERS is isolated from the floor with
which the top Of it is evcnthere being space of half
inch all around it. Exactly in the middle of this
slab and in the nadir of the telescope there morce
nine inches square and ten inches deep in which the ar
cial horizon is placed to protect it from the wind du
ring the adjustment for comaton, the determination
of the Of collimation, of level the adjustment
for stellar focus verticay of wres and the like with
the collimating eye-piece
An indispensable adjunct to a transit instrument is an
astronomical clock, to denote sdcreal time and here
stands the electric chronograph which invented by
Prof John Locke and ordered for this establishment
in ls4S as learn from inscription upon the instru-
men by Hon. John Mason, the then Secretary of the
Navy There is recording instrument similar to that
used in telegraph offices and the paper revolves dots
made upon it in line, about an inch from each
other the space between each representing second Of
time The manner in which these made is by the
passage of tho end of the pendulum through a bubble
of quicksilver as it swings back and forth, thus making
and breaking the electric circuit The observer holds in
his hand key, by means Of which he makes dots on
the paper at the instant of the passage of the stars
across the wires in the field OF view and in this man
ner he Is able to determine the right ascension of any star
to the hundredh of second This instrument is the
first application of this method of recording and by
its aid the making of star maps is much facilitated and
what of more Importance greater accuracy is obtained
than possible by the old methods.
In the south wing Of the building stands the prime
vertical transit which is not usc and we there
fore omit description of it, On this floor is also the
photograph room and the superintendent room. The
latter contains very extensive and valuable astronomi
cal library, and Normal clock made by Kessels of AL
tona from which all the other clocks in the establish
ment regulated 1t has gridron pendulum, and
the whole variation in its motion is less than eleven sec
onds year.
In the east wing of the building is the mural circle
made by Troughton Simms The telescope of this in
sument has objectgass of four inches clear aper
ture, with focal distance of FIVE feet The circle is Of
cast brass five feet IN diameter and the gaduatons are
marked on the periphery of the rim by lines parallel
with the axis of the circle. The rim has two bands
upon it, let in lush--the N plana on which the
degrees are numbered from up to 900 the other of
gold which the subdivisions are made for every five
ooscopes and the micrometer readings may be obtained
to tenths of seconds Of arc. The pier which it is
mounted nine feet high six feet long, aud three feet
wide 1t Is composed Of blocks of sandstone from the
Connecticut valley wrought smooth and closely cement
cd 1t supported on stone foundation eight feet by
five and extending clear of the floor through clay and
gravel, fourteen feet below the surface.
In the same room is the meridian circle, which rests
upon foundation of masonry, similar to those of the
west transit and mural circle, and is supported by granite
PIERS At each end of the axis and outside of each pier
circle thirty inches in diameter The finding circle
Is graduated only to Is minutes, and subdvided by
Verner to single minutes To it is attached the clamp
the binding of which passes through the pier the
tangent screw, for slow motion in decnaton acting on
the clamp carries with it the circle and telescope This
circle may be rotated upon the axis and is adjusted so
that the of ordinations corresponds to the zenith
The second circle graduated to three minutes and SUBJ
divided by four microscopes which read to single sec
onds and by estimation to tenhs of seconds This cir
Gle is left entirely free frsm clamps &C.. and is never
touched by the observer at any time. The telescope