128 
NATURE 
[Dec. 7, 1882 
adjustible in a direction to the right or to the left. The 
metallic circle within which the needle revolves is gra- 
duated on both faces, and is inclosed within an air-right 
case. The instrument turns upon a vertical support 
above a solid metal plate standing on three levelling- 
screws. A small loose level, which can be placed upon 
this levelling-plate, accompanies the instrument. The 
main novelty in Mr. Goolden’s instrument, consists, how- 
ever, in the arrangements by which the angle of dip may 
be determined without having either a horizontal gradua- 
tion or a horizontal compass needle upon the apparatus. 
It will be seen by reference to the figure that the vertical 
axis of the instrument is furnished witha spring-arm, which 
can be clamped to it by turning a screw, and that there 
are four metal studs affixed to the stand at equal 
distances apart, into any one of which the pin at the 
end of the spring arm can be pressed down. These 
arrangements serve to facilitate the following adjustments. 
Having levelled the instrument the spring-arm must be 
unclamped and the pin at the end of it- pressed down into 
the conical hole in one of the studs. While this is so 
held with one hand the vertical circle is turned upon its 
axis with the other hand wmtz/ the needle points directly 
Goolden’s simple dip-circle. 
vertically downwards to 90°. In this position, which is 
of course exactly magnetically East-and- West, the vertical 
circle is clamped by a turn of the screw. The position is 
verified by turning the whole circle and spring arm to- 
gether upon the axis until the pin meets the opposite 
stud, when the needle will again point vertically down- 
wards. The East-and-West position being thus verified, 
it is clear that the magnetic meridian will lie in a plane 
at right angles to this. Hence the next process is to turn 
the circle round and press the pin into one of the two 
studs which lie at right angles to the pair already em- 
ployed. The position of the needle in the circle is then 
read off. The circle is once more turned through a com- 
plete semicircle, the pin pressed into the opposite stud, 
and another reading is taken: the mean of these two 
being accepted as the true angle of dip. It will be seen 
that the usual elaborate processes of eliminating possible 
errors by reversing the needle-axis upon its bearings and 
reversing the magnetism of the needle itself are not 
attempted. Everything will therefore depend upon the 
accuracy of the adjustments of the instrument before it 
leaves the maker’s hands. 
readings are correct to within 10 minutes of arc. 
THE “COMET 
CHANDLER has made another approximation 
i\Y R 
I to the orbit of this comet, and now finds the fol- 
lowing ellipse (Sczence Observer) : 
As it is, it is claimed that the } 
Perihelion Passage September 17'2304 Greenwich M.T. 
Longitude of perihelion ... : 276 28 26'8 
e ascending node ... - 345 50 34°0 ae 
Inclination Sen ced ee aS. hs78 ED 
Loz. perihelion distance ... .-- 778835636 
Eccentricity . 0°9999700 
Retrograde. 
The period of revolution corresponding to this ellipse 
is about 4070 years ; in the middle of November there 
was a decided difference between the calculated and 
observed positions, part of which may be due to a cause 
to which Mr. Chandler has already drawn attention, viz. 
that the same point in the head of the comet may not 
have been always observed. We may now say pretty 
confidently that a short period of revolution is incon- 
sistent with the motion of this comet, and consequently 
that it is not identical either with the great comet of 1880 
or with that of 1843. Nevertheless we must repeat that 
there are indications of sensible perturbation during the 
flight through the coronal regions of the sun. 
Mr. Gill sends us some particulars relating to the early 
Cape observations of this comet. It was first detected 
by Mr. Finlay at five o’clock on the morning of Septem- 
ber 8, as he was returning to his house from the observa- 
tory. He went back and compared the nucleus with a 
small star in its immediate neighbourhood. On the fol- | 
lowing morning the comet was observed again, and the 
same day Mr. Gill sent the following telegram to Sir 
James Anderson, Chairman of the Eastern Telegraph 
Company :—“ Kindly tell Astronomer Royal, Greenwich, 
that bright comet was observed here yesterday morning 
by Finlay. Right Ascension this morning nine hours 
forty minutes, increasing daily nine minutes, Declination 
one degree south, increasing half degree south daily.” Mr. 
Gill acknowledges his indebtedness to the courtesy and 
liberality of Sir James Anderson for the free transmission 
of many previous messages. Unfortunately this one 
notifying the discovery of the comet in some way mis- 
carried, and did not reach Mr. Christie’s hands, so that 
the first intimation of the visibility of the comet came 
from Mr. Cruls at Rio de Janeiro, who, however, so far 
from being a discoverer, has informed the Academy of 
Sciences of Paris, through M. Faye, that he received 
notice of the comet’s presence from another quarter on 
September 10; it was not seen at the observatory of Rio 
till 5h. 15m. a.m. on September 12. 
Cloudy weather prevailed at the Cape between Sep- 
tember 10 and 17, and very few observations could be 
procured, and those had to be made by measuring the 
difference of altitude and azimuth from bright stars. On 
Sunday, September 17, the comet was easily visible with 
the telescope in full sunshine, and in close proximity to 
the sun. It was followed during the day by Mr. Finlay 
and Dr. Elkin, and towards afternoon was found to be 
rapidly approaching the sun. As the distance diminished 
“all appearance of tail was obliterated, only a round disc 
about 4” in diameter remained visible, but this was in- 
trinsically as brilliant as the surface of the sun, if not 
more so. Still closer this disc approached to the sun’s 
edge, and its disappearance there was observed just like 
that of a star when it was occulted by the bright limb 
of the moon.’’ Both Mr. Finlay and Dr. Elkin ob- 
served the disappearance, but though the former was 
using much the more powerful telescope, he only saw the 
nucleus five seconds longer than Dr. Elkin ; the comet 
| had passed on to the sun’s disc (not behind it, as 
Major Herschel erroneously assumes in NATURE last 
| week), but no appearance whatever of its presence there 
could be perceived. Mr. Gill himself was not able to 
arrive at this unique observation, having proceeded to 
| Simon’s Bay to meet Capt. Morris, R.E., on his way in 
the Zzewria to Brisbane to observe the transit of Venus, 
| who returns to South Africa as chief Executive Officer of 
| the Geodetic Survey of the Cape Colony and Natal; but 
