~ 
| “NATURE 
_diffased and hazy,” and adds that it had moved through six 
minutes of are in a wortherly direction, contrary to what was 
stated in his telegram, The approximate place for 5h. 52m. 
mean time (as we take it) was in R.A. sh. 18m. 8s,, Decl. — 14° 
18’, showing that a southerly motion was intended. In his 
s:cond letter Dr. Bone says: ‘‘I should place the magnitude at 
about 2°5, for it was vis‘ble to the naked eye in first twilight ;” 
_ though the telegram has what in this case was somewhat unneces- 
sary information: ‘* No asteroid in that place.” 
An observation of this kind wonld hardly perhaps have 
required strict examination, were it not that about thirty-eight 
hours Jater br, Bk. A. Gould, at Cordoba, compared the comet 
“with an object which he could not afterwards identify, and after 
much hesitation, through fearing some great error, he communi- 
cated the particulars to the Astronomische Nachrichten, No. 
2384. We have already referred to these observations in this 
column (NATURE, vol. xxiv. p. 342). At1oh. 58m. gs. sidereal 
time, on June 11, Dr. Gould made a rough preliminary deter- 
- mination of the comet’s place, for the purpose of finding a com- 
parison-star, when he says he found one in the field ; with this 
star he compared the comet four times, the results being :— 
Cordoba Sidereal Time. Comet followed. Comet South. 
He tle ‘S. Ss mee 
ir $8 49 ES 5 12°9 
ED) gett) ac -¥ees C40 5 Se 
OAT Obs sss) AO 5 85 
eae MeV ae] 48°5 5 2°38 
The rough place of the comet by the circles of the equatorial, 
agrees sufficiently well with that we now know it must have 
occupied at the time, but if the comet had been observed during 
_ the micrometrical comparisons, the position of the supposed star 
would have been 5h. 10m. 23s., Decl. —9° 29'°8, where no star 
has been catalogued, though Dr. Gould thought it would hardly 
be below the third magnitude, and he could rather believe it as 
bright as the second. 
In Zhe Observatory for January, Mr. Christie has printed a 
letter from the able amateur, Mr. John Tebbutt, of Windsor, 
New South Wales, suggesting an explanation of Dr. Gould’s | 
He made four circle-com- | 
observation which merits attention. 
parisons of the comet with Rigel on the morning of June 12, the 
Jast of which was only 1h, 29m. of absolute time previous to the 
first observation at Cordoba, and he states ‘‘there was then, I am 
confident, no object near the comet answering to the description 
already given.” Were it not that the Cordoba instrumental 
place agreed closely with the actual position of the comet, he 
adds, he would be disposed to suggest that Dr. Gould had not 
observed the comet with the micrometer at all, but possibly the 
two stars, B.A.C. 1592 and 1597, ‘*;whose relative magnitudes 
and position agree almost exactly with his observations, and 
whose differential declination would gradually diminish from the 
effect of refraction as the : tars approached the horizon.” 
We will now examine the case with some strictness. The 
following positions of the comet are calculated from the elements 
published by Mr. White, of the Melbourne Observatory, and 
will be very nearly correct for the dates in question :— 
True R.A N.P.D. . distan 
G.M.T. hm s ae eis naniae Earth. 
June 9°5 5 9 23°9 ... 104 57 5 9°59144 
10°0 5 9505 ... 103 39 30 Q'55131 
10°5 5 fO1or2 3.) 162 17 55 9°57121 
11‘o 5 10 469 ... 100 51 6 9°56116 
115 5 11 16% ... 9919 59 9°55121 
12'0 Bur woes... Oya ie 9°54139 
From the ephemeris, it follows that the comet’s motion between | 
Dr. Gould's first and last comparison was +-0s.*41 in R.A., and 
+44"°7 in declination. The observed difference in declination 
was only 10"'1, 
difference of refractions of comet and star would have been 
about 028s. and 2"°6 at the first comparison, and 0*47s. and 4”°3 
at the last, so that the discordance between observed and com- 
puted motion would not be explained by the refraction. 
The stars referred to by Mr. Tebbutt are Bradley 718, and 
69 A Eridani, and both are found in Mr. Stone’s recently 
published catalogue, ‘Their apparent places on June 11 were :— 
: RA. Decl. 
»m. s. s ‘ a“ 
Br. 718 5 2 39 06 —S 49 14°6 
A Eridani ER SR REY pls) -8 54 278 
If now, Dr. Gould, in ‘‘the exceptionally thick haze and mists 
If Dr. Gould had observed the comet the | 
«| Agere 
of the horizon,” and bright twilight which he mention:, mistook 
A Eridani for the comer, and compared: with Bradley 718, we 
have the following striking agreement :— r 
In R.A. In Decl. 
Ss. r 
Differences of above places +48°8 a 1372 
By Gould’s comparisons ... ... +486 ... -5 87 
| Difference of refractions at first comparison, 0°7s. and 6°”5, and 
at the last comparison, 1°7s. and 15°”7, so that the ten seconds” 
change in the difference of declination measured with the micro- 
meter is accounted for by refraction, and there is a tendency to 
diminishing difference of R.A. in the comparisons, which re- 
fraction would necessitate. Dr, Gould states, that these com- 
parisons were all he could obtain ‘‘before the comet passed 
below the horizon,” and the true altitude of A Eridani at the 
last of them was 2° 17’: the altitude of the comet at the same 
time being 4° 15’. 
Mr. Tebbutt thinks, if his suggested explanation be accepted, 
it will be necessary to admit ‘‘a temporary outburst in the light” 
of B.A.C. 1592 (Bradley 718), and it happens that there is some 
reason for believing that star to be variable. It is a widedouble 
star, No. 649 of the Dorpat catalogue. Sir John Herschel, in 
one of his sweeps at the Cape of Good Hope, on December 26, 
1836, estimated the principal component 7°8 (the companion is 
about 1om.): it was rated 6°0 by Struve, 6°$ by Jacob in 1849, 
and 6 or 7 by Lalande, Bessel, Knorre (in his Berlin chart), 
Santini, and others, but in Mr. Stone’s new catalogue it is called 
5m., or only one magnitude less than A Eridani, which has been 
pretty consistently estimated a fourth. 
It appears, then, that Mr. Tebbutt’s explanation of the diffi- 
culty in Dr. Gould’s case, is a very probable one: the instru- 
mental comparison preceded the first micrometrical observation 
about ten minutes, and the assumption of course will be. that 
| after applying the micrometer, the telescope, instead of being 
| pointed to the comet, was turned upon the stars alluded to 
| above, which, in the dense haze, were blurred and confused. 
| With respect to the observations at Castlemaine, Victoria, on 
June 10, it is to be regretted that Dr. Bone has not com- 
municated the comparisons of the comet with star as 
entered in his note-book, and his letters having been 
| given. publicity in the official periodical of the Royal Astro- 
nomical Society, it is desirable that these should be for- 
| warded, that the true explanation may be found. His geogra- 
phical posicion is given in a note on the last Transit of Mercury, 
wh'ch appears in the same number of the A/onthly Notices = 
| longitude 9h. 36m. 55s. E.., latitude 37° 4’ 11” S. ; that pheno- 
menon was observed with a 4°7 inch (Wray) equatoreal, which 
| it may be presumed was the instrument used for observing the 
comet. It so happens that observations were made the same 
evening at the Melbourne Observatory, and the earlier com- 
| parisons at the same time that Dr. Bone was similarly employed 
at Castlemaine, which is only 3 min. west of Melbourne. The 
| Melbourne reference star was at first 8. Lepori:, the apparent 
place of which was in R.A. 5h. 8m. 42s., Decl. —14° 2’ 25’, 
therefore in the same R.A., and only 15’ north of the position 
which Dr. Bone assigns to the moving object at 5h. 52m. M.T. 
It is difficult to explain how such an object could have escaved 
the attention of the Melbourne observers, while they were com- 
paring the comet wih a star so close to its place. The position 
of the real comet may he interpolated from the above ephemeris, 
or it may be inferred from the Melbourne observations the same 
evening. The second series of comparisons were made with a 
star which we find to be No. 173, Hour V. of Weisse’s Bessel, 
and reducing this series we have for the comet’s place :-— 
Melbourne M.T. gi R.A. 
hams SS 0 be “cp oa 
June 10 at 6 3 136 5 9 40°83 —14 3 22°1 
Comparing this with the result of the earlier measures from 
8 Leporis (Afonthly Notices, vol. xli. p. 432), we have the fol- 
lowing positions of the comet for Dr. Bone’s times :— 
App. Decl. 
RA. Decl. 
h. m hm. s. ovr 
At 5 52 5 9 40°5 -14 4! 
6 45 59 42°7 —13 58 32 
At 5h. 52m, its true altitude was 8° 54’, but it set at 6h. 41m., 
four minutes before the list observation at Castlemaine. With 
Dr. Bone’s place for his object it would be 1° above the horizon 
at this observation. Refraction would of course have been 
exercising a great effect upon any comparisons made neat so 
