The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1856-09-07

II Is here shown that the clocks do not uniformly
for five minutes of tme but whether the be entire
ly due to the inferior clock cannot be decided.
strong suspicion is thus excited that there
are variations even in the best clocks amount.
ing to fifteen twenty thousandths OF second
Of time in short Intervals and quite hey ond the reach
detection by the old methods. The Professor pro
ceeded to explain the necessity OF rigid scrutiny into the
possible irregularities which might exist in all the nsru
mental and some account of the methods
during the nights observations read at pleasure each OF
his instrumental errors. The curious subject of
sonal equation" was now discussed This personal
equaton, as it is termed by astronomers, Is pretty
nearly constant difference found to exist between all OBJ
in noting by the clock the time Of
The star the meridian wire of the tee
scope. Professor Mitchell explained curious method by
which not only this difference as between two indvdu
ais mgn' oe teru anu pnpay oo, aa wnou.
person for himself could determine his own abso-
lutte personal diosyncrasy in the particular This
The Professor now passed to the nsderaton OF the
second great element in fixing the places OF the
usual methods for the Of large and small
arcs in N D. and then the speaker passed to the pre-
senaton OF the results obtained during the past three
months by the new apparatus of the Cincinnati observa
tory The observations were all dlerentia and depend
ed the place Of Nautical Almanac star The gre
facility of the method shown In the fact that dur
ing the past three months working about three
each clear night less than ten thousand obser
in right ascension and north polar distance had been
corded The stars were all confined to of thirty
minutes Of arc In breadth, and six hours OF
right ascension: AS specimens Of the delcacy Of the
pcTloImAuCo VI tue new lnSuumcnt called Dy the
Professor the declinometer, series of measures
the brighter stare Of the Peiades presented in
which the average discrepancy between the places given
by the method and those determined by Bissel with
tho celebrated helometer If Koengsburg only amounted
TO four tenths OF second Other observations
were now presented Of other groups Of stars amounting
to twenty i've to thirty group and coming within Of
teen to thirty minutes Of tme-one group four hours in
right ascension from the standard star another two hours
removed and the third Immediately preceding the stand
ard-some had been observed many ten times and
none less than three times. The alterations numbered
braa ht,1r al t.a
mean, or the average, ,ted, in the Ple
adcs, to four tenths of one second Of arc. The
declimometer had a'so been brought into exact
comparison with the mcrometer OF the great ca
toral Of the Cincinnati Observatory both double
and on measures Of the intervals between the opposite
diagonal angles OF crt SO in the coimotor and the
suit showed an nvariable superiority in favor of the
declinators. These measures carefully explained
In all their details Some general exclamation was now
given of the simple mechanical arrange rents whereby
these results had been reached. Believing, after vast
series OF measures, the micrometer to be
able the Professor had gone back 10 first principles
and had so maenihed angular motion mechanically, as
really to read the degrees, minutes and seconds,
thouga read at the extremity Of radius OF five hundred
and forty feet IN length On such circle the single
second OF arc became large that its tenth part cou be
rad by the unaded eye with considerable precision. Tho
Professor after closing the description OF the mechanical
construction Of the instrument gave account OF
series OF observations made for the purpose OF determn
ing the changes from hour TO hour the figure OF his
new decnaon arm, and OF the tubes OF the telescope
Some OF the results were very uexpcabe to him. show
ing the fact that the lower extremity Of a wooden arm
~ feet In length clamped TO decnaton axis OF the
equatorial his INSTRUMENT being itself firmly clamped)
experienced a sensible daily change slowly moving
Forth and south each ~ hours and reaching ts maxi
mum northern molten AT IL O'Clock, between IL aud
O'Clock, eight days out OF ten and the exceptional
days sfactory could be assigned tho
exception. The delicate changes found be
constantly In progress in the figure OF the tube OF the
telescope and those changes did follow remote
~ the changes Of either the Thermometer the hgrome
ter. This machinery was entirely new and had not been
examined by any Of the members Of tie Association de-
voted TO astronomy.
The Rev Mr. Hi, OF Massachusetts, made some state
ments the close OF Prof Mltches report, affirming
the exceeding delcacy Of the mechanical arrange
meLts, which he had personally examined a few weeks
since at the Cincinnati Observatory.