EL2 
NATURE 
| Mov. 30, 1882 
which, further, should be provided with all that is neces- 
sary for the establishment of the stations, the safety and 
the subsistence of the observers, should not leave those 
regions before bringing the mission to Tahiti, where our 
envoyés would find means of transport for their return, 
either by the way they went, or (which would seem prefer- 
able), by way of Australia. 
THE TRANSIT OF VENUS ON WEDNESDAY, 
DECEMBER 6 
T the Transit of Venus in 1874 the tables of the 
planet prepared by Prof. Hill appeared to have a 
decided advantage over those of Leverrier. The correc- 
tion to the tabular place deduced from the observations. 
of the transit is in close accordance with that shown by a 
meridian observation at Washington on the day preceding 
the phenomenon. Although the entire discordance was not 
negatived by the tables of Prof. Hill, they went far towards 
removing it in 1874,and as the coming transit (December 6) 
will take place in nearly the same point in the planet’s 
orbit, we shall assume in what follows, that the tables of 
the American astronomer will again be fairly correct. 
Prof. Newcomb assumes and probably with much reason, 
that the error of Leverrier’s tables will prove to be an 
increasing one, and is therefore inclined to apply a still 
larger correction to the place deduced from them. It 
may be mentioned that the calculations of the transit in 
the Nautical Almanac, the Connaissance des Temps, and 
the Berliner Astronomisches Jahrbuch, depend upon 
Leverrier’s tables. For the diameter of the planet we 
adopt that found by Prof. Auwers from heliometric 
measures in Egypt during the last transit, combining it 
with the diameter of the sun, inferred by Leverrier from 
his discussion of the transits of Mercury. 
Direct calculations for Greenwich, Edinburgh, and 
Dublin give with the elements so obtained the following 
Greenwich mean times of the first external contact, and the 
respective angles from the sun’s vertex for direct image :— 
newest, ER ° D 
Greenwich ~....°-... 2 ‘o)42°2 126 59°4 
dinburote ss ss. 92) 4727 130 49°3 
Dublin S65, Soh A OHS) 131 21°2 
For a limited area like that of these islands we may apply 
to these times and angles, the method of distribution of 
predictions given by Littrow, and subsequently by Wool- 
house. Putting the latitude of any place within the above 
area= 50 +L, and its longitude in minutes of time 
= M, + if east of Greenwich, — if west, we get the fol- 
lowing equations :— 
oatt. eet a } = 2h. 0°62m. + [$°7453] L — [8 1402] M. 
Ae ee age | = 1253 + 66 L ~ [0136] 
The quantities within the square brackets are logarithms, 
but of course if preferred the factors for L and M may 
be expressed asnumbers. As an example of the applica- 
tion of these formule, suppose the time of first contact 
and the corresponding angle are required for Norwich, 
the position of which place may be taken in latitude 
+ 52° 38’, longitude 1° 18’ or + 5m. I2s., we have then 
L= + 2633 M= +5:20m. 
+ 8°7453 | — 81402 
| 
| 
Log. L Log. M + 0°7160 
— 88562 
Nov i. — 0072 
m. s 
20°69 or 2 0 41 G.M.T. 
Longitude E 5 12 
25 53 
Norwich M.T. 
: : 
much valuable and interesting work could be done. 
For the angle— 
+ 9°669 = 9°136 | + 1°23 
Log. L + o'421 | Log. M+0'716 | — o'71 
——_ | ——— | 126°3 
+ 10090 | — 9852 
126°8 ... angle from vertex. 
So that according to the calculation the limb of the planet 
comes into first contact with that of the sun at 53° from 
his lowermost point towards the left, as we view the 
phenomenon with the naked eye. It will be remarked 
that there is less than a half minute difference in absolute 
time between Greenwich and Dublin, and considering 
the possibility of error of many seconds in any prediction 
that can be made for geometrical contact and the difficulty 
of always determining what is geometrical contact in the 
observations, our formula for time of first contact is more 
than a sufficient one. 
For first zferza/ contact, it may be assumed that 21 
minutes have to be added to the time of external contact 
at any place in these islands; while for the angle from 
N. point of first external contact may be taken in all 
cases 147°. 
In the national ephemerides the times of the contacts 
are given for a particular meridian as they would be noted 
at the centre of the earth, and formula are appended to 
reduce these geocentric times to any point upon the 
earth’s surface. It is obvious that where, as in a transit 
of Venus, predictions are required for such widely distant 
stations, this method possesses the greatest convenience. 
NOTES 
THE following are the Lecture arrangements at the Royal Institu. 
tion for theensuing Session :—The Christmas Lectures will be given 
by Prof. Tyndall, on Light and the Eye. Lefore Easter—Prof. W. 
C. Williamson on the Primeval Ancestors of Existing Vegetation, 
and their Bearing upon the Doctrine of Evolution; Prof. R. S. 
Ball, four lectures on the Supreme Discoveries in Astronomy ; 
Prof. Dewar, nine lectures on the Spectroscope and its Applica- 
tions ; Mr. R. Bosworth Smith, four lectures on Episodes in 
the Life of Lord Lawrence ; Dr. W. H. Stone, three lectures on 
Singing, Speakinz, and Stammering; Mr. H. H. Statham, 
two lectures on Music as a Form of Artistic Expression. After 
Ea-ter—Courses will be given by Professors Tyndall, McKen- 
drick, A. Geikie, and Turner (of St. Petersburg). The Friday 
Evening Discourses will probably be given, among others, by 
Mr. R. B. Smith, Dr. G, J. Romanes, Sir W. Thomson, Mr. 
M. D. Conway, Prof. W. C: Williamson, Mr. W. H. Pollock, 
and Prof. Tyndall. 
A COMMITTEE, consisting of the Right Hon. J. T. Ball, 
LL.D., D.C.L., the Very Rev. W. Reeves, D.D., Dean of 
Armagh, J. L. E. Dreyer, Ph.D., Astronomer of Armagh Ob- 
servatory, has been appointed by the Governors of the Armagh 
Obs-rvatory to raise a fund for the purpose of erecting a memo- 
rial instrument in the observatory at Armagh, where the late 
Rey. Dr. Robinson spent fifty-eight years, engaged in those 
scientific investigations with which his name will be for ever 
associated. The Committee addresses its appeal not only to the 
inhabitants of Ulster, or of Dublin, but to Robinson’s friends and 
adwirers all over the United Kingdom. The services rendered 
| to astronomy by Dr. Robinson are well known, and doubtless 
many of our readers will be glad to aid in paying a tribute to 
his memory. It is proposed that the memorial take the form of 
an equatoreal refractor, say of eight or nine inches aperture, 
which could be had for about 500/., and could find room in one 
of the existing domes at Armagh. With such an instrument, 
Subserip- 
tions should be sent to Dr. J. L. E. Dreyer, Observatory, 
Armagh. 
