Fune 11, 1885] 
NATURE 
139 
Since last October transits of the close circumpolar stars have 
-been taken at the middle wire set to successive revolutions of the 
R.A. micrometer, thus virtually introducing a system of very 
close equidistant wires for the slow-moving stars. It is thus 
found that a larger number of separate observations can be ob- 
tained in a moderate time, a point of special importance in 
changeable weather. The equality of successive intervals of the 
R.A. micrometer-screw was tested last January foreach revolution 
through a range of twelve revolutions, and also for every tenth 
of the three middle revolutions, and the errors of the screw 
appear not to exceed the errors of observation. The determina- 
tion was made by means of the south collimator, the eye-piece 
ofthe transit-circle having been turned through 90°. The ob- 
servations of close circumpolar stars have also been discussed 
" with a view of testing the equality of succeSsive revolutions of 
the R.A. micrometer screw, the results being very satisfactory. 
The screws of the microscope-micrometers also were examined 
. by means of the south collimator on March 27 and following 
days, successive intervals being measured for each revolution 
‘ and third of a revolution from—1' to 6". Though there is 
f evidence of considerable wear in the individual screws, which 
have been in constant use since 1875, the methcd of using them 
4 (the action of the spring being in opposite directions for the 
£ micrometers of each pair) entirely eliminates this effect from the 
; mean, and the resulting errors (which are probably casual 
errors of observations) do not exceed 005 at any part of the 
screws. 
The subjects of meridian observations in the past year have 
been as usual the sun, moon, planets, and fundamental 
stars, with other stars from a working catalogue, which now 
contains about 2,750 stars. About 380 stars have been lately 
added to the list from the ‘‘ Harvard Photometry,” with a view 
of making the forthcoming Greenwich Catalogue of stars down 
to the sixth magnitude as complete as possible. It is hoped 
that all of these stars will have been sufficiently observed by the 
end of 1886, when it is proposed to form a Ten-Year Catalogue, 
epoch 1882‘0. The annual catalogue of stars observed in 1884 
contains about 1,370 stars. 
The following statement shows the number of observations 
with the transit-circle made in the twelve months ending 1885, 
May 20: 
! 
Transits, the separate lim)s being counted at separate 
observations... a a2 eee nee te, 552 
Determination of collimation error... es He, 20) 
Determinations of level error ... ae He aoe 
Circle observations ae os aa as ne g2n 
Determinations of nadir point, including the number of 
circle-observations ... 
Reflection-observations of stars (similarly included) A 619 
The discordance between the nadir observation and the mean 
of the results from reflection observations of stars north and 
south of the zenith has recently become very small, the correction 
deduced for the first four months of the present year being only 
—0”'07. The mean correction indicated by the observations of 
1884 was — 0-36, whilst those of 1883 gave the value —0’"45. 
The steady increase of this discordance from 1878 to 1883 and 
its subsequent decrease remained unexplained, no change having 
been introduced into the method of observation of the nadir 
point or of stars by reflection during the last two years. 
The apparent flexure of the transit-circle, as found by means 
of the collimators, has again changed sign. From six deter- 
minations made on 1884 June 3, Sept. 9, Sept. 29, Oct. 5, 
Oct. 20, and May 20 (the reversion-prism being used on each 
occasion except the first) the resulting values (found by four 
. different observers) are —0""47, + 1''00, + 0”°03, + 010, and 
+o0"'o08, the mean of which is +0'°17, agreeing closely with 
the value + 0°13 found by nine accordant determinations in 
the period 1879 to 1882, whilst the mean of five determinations 
by three different observers in 1883 gave the value — 0°49. No 
correction for flexure (as distinct from the R—D correction) has 
been applied to the observations since 1879. 
The correction for R — D, the error of assumed colatitude, and 
the position of the ecliptic, have been investigated for 1884. The 
computation of the geocentric and heliocentric errors for the 
planetary results is not yet complete. 
The correction for discordance between ‘reflection and direct 
observations of stars, deduced from observations in 1884 which 
extend from Z.D. 69° north to Z.D. 70° south is — 0”*02 + 0°66 
sin Z.D, The assumed formula ae + ¢ sin =z represents the 
observations of 1884 satisfactorily throughout the whole range 
of zenith distance. 
The value found for the colatitude from the observations of 
1884 is 38°. 31.2191, differing only by 0” or from the assumed 
value ; the correction to the tabular -obliquity of the ecliptic 
is + 0”°57; and the disGordance between the results from the 
summer and winter solstices is — 0” 99. 
The mean error of the moon’s tabular place (computed from 
Hansen’s Lunar Tables with Prof. Newcomb’s corrections) is 
+0s‘02 in R.A. and + 029 in longitude as deduced from 104 
meridian observations in 1884. 
Altazimuth.—The observations with this instrument have been 
restricted to the period from last quarter to first quarter in each 
lunation, the total number of observations of various kinds made 
in the 12 months ending 1885 May 20 being as follows :— 
Azimuths of the moon and stars ... ... ... «. 321 
Azimuths of the azimuth-mark  ... ... ... 181 
Azimuths of the collimating-mark wa gp 192 
Zenith-distances of the moon ae 178 
Zenith-distances of the collimating-mark 196 
Since last December a ‘“‘reversion prism” has been used to 
reverse the apparent direction of motion in the observation with 
lamp right and in that with lamp left on alternate nights. 
Clocks.—On Jan. 1 the public clock at the Observatory 
entrance and the other mean solar clocks were put forward 12 
hours so as to show Greenwich civil time, starting at midnight 
and reckoning from oh. to 24h., which would correspond with 
the universal time recommended by the Washington Conference. 
The change from astronomical to civil reckoning has also been 
made in all the internal work of the Observatory, and has been 
carried out without any difficulty. Greenwich civil time is found 
to be more convenient on the whole for the purposes of this 
Observatory, but its introduction into the printed astronomical 
observations has been deferred to allow time for a general agree- 
ment amongst astronomers to be arrived at. It is proposed, 
however, to adopt the civil day without further delay in the 
printed magnetical results, thus reverting to the practice previous 
to 1848, and making the time-reckoning harmonise with that 
used in the meteorological results, the reckoning from oh, to 24h, 
being for the future adopted in both cases. 
Reflex Zenith Tube.—The observations of + Draconis for deter- 
mination of the temperature correction have been continued, 
and about 45 transits over the 30 wires have been observed at 
temperatures ranging from 46° to 72. Seven transits of 9. 
Aurigz were also observed last February at low temperatures 
ranging from 42° to 56. 
£quatorials.—The work on the Lassell equatoreal has occu- 
pied a great deal of attention during the past year, a number of 
repairs and alterations having been required in order to get the 
instrument into proper working order. The driving clock, which 
was found to drive the instrument at only three-fifths of the 
proper speed, has been altered, a slow motion in R.A. (to be 
worked from the observing stage) has been contrived, a new 
slide of improved construction has been made for gearing the 
driving-screw into the hovr-circle, the teeth of the hour-circle 
have been re-cut, a firm declination clamp has been applied, an: 
improved edge suspension fur the large mirror (consisting of a 
steel band which encircles the mirror and is supported by 
brackets at six equidistant points of the circumference) has been 
contrived, a new and firmer mounting of the small mirror has 
been made, and the eye-piece has been mounted firmly on a 
plate which allows it to be tilted in any direction, for optical ad- 
justment. The framed ir nm base which supports the instrument 
has been bricked up and filled with concrete, and this, with the 
other alterations, has greatly increased the stability of the tele- 
scope, which is now quite satisfactory. Difficulty is, however, 
still experienced from want of stability of the optical axis of the 
large mirror, which requires to be readjusted continually, as the 
telescope is moved. When the mirrors have been properly ad- 
justed the definition appears to be very good, the companion to 
Vega being shown with remarkable distinctness without any 
trace of scattered light from the large star. 
The south-east and Sheepshanks equatorials are in good order, 
as also is the Simms’ six-inch equatorial mounted in the south 
ground. 
With one or more of these equatorials, or with the altazimuth,, 
30 occultations of stars by the moon (19 disappearances and 11 
reappearances, including 7 disappearances and 9 reappearances 
during the lunar eclipse of October 4), and 57 phenomena of 
