140 
Jupiter’s satellites, have been observed in the twelve months 
ending 1885 May 20, and the observations have all been com- 
pletely reduced to the end of 1884. Comet (c) 1884 has been 
observed on four nights, the Lassell reflector or one of the other 
equatoreals being employed, and some measures of distances and 
position-angle of double stars, as well as a large number of ob- 
servations for determining the value of 1°’. of the screw in 
different parts of the field of view have been made with the Airy 
double-image micrometer mounted on the Sheepshanks’ or 
Simms’ equatorial. 
Micrometer measures of some of the satellites of Saturn (in- 
cluding Enceladus) were made on seven nights with the Lassell 
equatorial. 
Spectroscopic and Photograthic Observations.—The solar pro- 
minences have been observed with the half-prism spectroscope 
on only two days, the photographic reductions having pressed 
very severely on the spectroscopic assistant during the long con- 
tinued maximum of sun-spots. 
For the determination of motions of stars in the line of sight, 
569 measures have been made of the displacement of the F line 
in the spectra of 47 stars, and 72 measures of the 4 lines in 14 
stars, besides measures of the displacements of the 6 and F lines 
in the spectra of the east and west limbs of Jupiter, and of the 
east and west ansz of the rings of Saturn, and comparisons with 
lines in the spectrum of the moon, or of the sky, made in the 
course of each night’s observations of star-motions, or on the 
following morning, as acheck on the general accuracy of 
the results for star-motions. The observations of the last 
twelve months confirm the change in the motion of Sirius, 
which now appears to be approaching the sun at the rate 
of about 20 miles a second. As there is great difficulty 
in the use of a pointer or cross-wires for measuring both 
the broad dark line in the star’s spectrum and the narrow bright 
comparison line, Mr. Maunder has suggested the use of a rever- 
sion spectroscope (on the double-imsge principle) for these ob- 
servations, and Prof. Pritchard has kindly lent the reversion 
spectroscope of the Oxford University Observatory, in order 
that the suitability of that form of instrument may be tested. The 
spectroscopic observations of all kinds are completely reduced to 
the present time. 
In the twelve months ending 1885 May 20 photographs of the 
sun have been taken on 173 days, and of these 431 have been 
selected for preservation, the record being not so complete as 
usual, owing partly to the loss of several days during the adjust- 
ment of the instrument after the adaptation of the secondary 
magnifier, and partly to a failure of the supply of dry plates in 
July last during the absence of Mr. Maunder. There were only 
two days on which the sun’s disk was observed to be free from 
spots. 
The mean spotted area of the sun was slightly less in 1884 
than in 1883 and slightly greater than in 1882, whilst the faculze 
in 1884 showed a slight increase as compared with 1883, and a 
slight falling off as compared with 1882. It would seem that 
the maximum both of sun-spols and faculee occurred about the 
end of 1883 or beginning of 1884. 
For the year 1884 Greenwich photographs are available for 
measurement on 152 dsys, and Indian photographs filling up the 
gaps in the series on 159 days, making a total of 311 days out 
of 366 on which photographs have been measured. In 1883 
the total number of days was 340, viz., Greenwich series 215 
days, supplemented by Indian photographs received from the 
Solar Physics Co nmittee on 125 days. 
Magnetic Instruments.—The following are the principal 
results for magnetic elements for 1884 :— 
Approximate mean westerly 
declination 18°.8'. 
- { 3°93r (in English units). 
Mean horizontal force “7-812 (in Mere anits,) 
: { 67.20. 8 (by 9-inch needles). 
Mean dip - 67.29.32 (by 6-inch needles). 
2 67. 30. 9 (by 3-inch needles). 
In the year 1854 there were only five days of great magnetic 
disturbance, but there were also about 20 days of lesser disturb- 
ance for which it appears desirable to publish tracings of the 
photographic curves. It may be interesting to add the tracings 
fora few quiet and nearly quiet days in order to exhibit the 
characteristics of the ordinary diurnal movement. 
Commencing with 1883 the magnetic diurnal inequalities of 
NAT ORE 
[| ¥une 11, 1885 
declination, horizontal force, and vertical force have been dis- 
cussed by the method of harmonic analysis, the harmonic 
expressions for these inequalities being obtained for each month 
and for the year with arguments expressed in apparent solar time 
as well as in mean solar time. 
Meteorological Observations.—The mean temperature of the 
year 1884 was 50°°7, being 1°°4 higher than the average of the 
last 43 years. The highest air temperature (in the shade) was 
94° on Aug. 11, and the lowest 24°°5 on Noy. 25. The 
mean monthly temperature was above the average excepting in 
the months of April, June, Oct. and Nov. 
The mean daily motion of the air in 1884 was 286 miles, 
being 3 miles greater than the average of the last 17 years. The 
greatest daily motion was S91 miles on fan. 23, and the least 78 
miles on Feb. 8. The only recorded pressure exceeding 20 Ibs. 
on the square foot in 1884 was 22°7 lbs. on Jan. 23, after which 
the connecting chain of the pressure plate broke, as mentioned 
in the last report. It is probable that greater pressures occurred 
afterwards on the same day, and also in the gale of Jan. 26, at 
which date the chain had not been renewed. 
During the year 1884 Osler’s anemometer showed an excess of 
about 25 revolutions of the vane in the positive direction 
N, E, S, W, N, excluding the turnings which are evidently 
accidental. A 
The number of hours of bright sunshine recorded by Camp- 
bell’s sunshine instrument during 1884 was 1115, which is about 
100 hours less than the average of the seven preceding years. 
The aggregate number of hours during which the sun was 
above the horizon was 4465, so that the mean proportion of 
sunshine for the year was 0°250, constant suushine being 
represented by 1. 
The rainfall in 1884 was 18’0 inches, being about 7 inches 
below the average of the last 40 years. ; 
Chronometers and Timz Signals.—The number of chrono- 
meters now being tested at the Observatory is 151, and of these 
103 (79 box-chronometers, 13 pocket-chronometers, and If 
deck-watches) belong to the Navy, 40 are placed here for the 
annual competitive trial, and § are on trial for purchase by the 
Austrian Government, 
The first six chronometers in the competitive trial of 1884 
were rather above the average of the last ten years as inferred 
from the trial numbers. As niuch difficulty is experienced in 
maintaining the chronometer oven at a nearly constant tempera- 
ture, an apparatus has been procured from Mr. Kullberg which 
is designed to effect this automatically, by the action of a com- 
pensation-bar, which, as the temperature rises, gradually closes 
a small hole through which the supply of gas to the gas burners 
passes. The apparatus has not yet been brought into use, as 
the chronometer oven has been constantly required for testing 
chronometers since it has been received. 
The automatic drop of the Greenwich time-ball failed on 6 
days through the clock-train stopping. The ball was not raised 
on 3 days on account of the violence of the wind. 
As regards the Deal time-ball, which is now dropped by cur- 
rent passing through the chronopher of the Post Office tele- 
graphs, there have been fourteen cases of failure owing to inter- 
ruption of the telegraphic connections, and on one day the 
current was too weak to release the trigger without the assist- 
ance of the attendant. - 
In connection with the establishment of hourly time signals at 
the Start or Lizard, which was long advocated by Sir G. B. Airy, 
I have received from the Committee of | loyds’, in answer to 
my inquiry, an assurance that that corporation would be willing 
to undertake the maintenance of hourly time-signals at any of 
their signal-stations, provided the Government would supply the 
necessary apparatus. After consultation with Capt. Wharton, 
it has been thought better that, before taking further steps, some 
preliminary trials should be made of a collapsible cone as an 
hourly time-signal, facilities for doing which exist at Devon- 
port. As regards ball-drop or other time-signal, I would 
propose that it should be made automatically by a local 
clock, to be corrected daily by the help of a time-signal from 
Greenwich at 10 a.m., which should automatically start an 
auxiliary seconds pendulum, suspended freely just behind the 
clock pendulum. The attendant would then accelerate or 
retard his clock pendulum (by electro-magnetic action as in the 
Greenwich mean solar clock) so as to make it pass through the 
middle of its vibration at the same time and in the same direc- 
tion as the auxiliary pendulum, and thus to indicate accurately 
Greenwich mean time. A return signal to Greenwich sent by 
