516 
Elements. 
T =1914 Feb. 117518 Berlin M.T. 
@—J200" 920. 
(2 =265° 45°3' ;1914'0 
z= 36° 19°3' 
log g =0°13179 
The comet is getting very faint, but for those with 
larger telescopes the following ephemeris may be use- 
ful :— 
ah (true) Decl. (true) Mag. 
July 16 V7) 50) 22 ee OMsGo 12-9 
Typ ae acd 49 24 21-6 
TO) aaete ASPAS |) ae 12:9 
LOW Janos WSmige kas eGy 6 S455 13:0 
Z2ONeerae AT EAIMG eo R50 
PR ce Ng RON Racks 48:5 
PAE Wc AG EL Mkt 41-0 
Be 817-40 Th Seon ag 13:1 
Comet 1913f (DELAVAN).—For the last few months 
comet 1913f (Delavan) has been lost in the sun’s rays, 
but it will soon now become visible again, and it is 
expected that it may appear as a naked-eye object. 
Numerous elements, both parabolic, elliptic, and hyper- 
bolic, have been computed by different workers. Thus 
Dr. G. van Biesbroeck advocates parabolic elements 
(Astronomische Nachrichten, No. 4739) as follows :-— 
T=1914 Oct. 26°3000 Berlin M.T. 
@=—977 28 17°4 | of 
Q=59° 8’ 46:4”; I1910°0 (Osc. 1914 Sept. 280) 
Z =68° 1’ 46-4") 
log g =0°0430113 
Herr E. E. Kiihne calculates his ephemeris (Astro- 
nomische Nachrichten, No. 4739) on the basis of 
elliptic elements, which he gives as follows :— 
T =1914 Oct. 26°5626 Berlin M.T. 
@ =97° 27’ 87") 
(HE Forno, 104) 9- 19040 
7 =68° 6! 230") 
log g =0'043697 
€ =0'999655 
Messrs. S. B. Nicholson and C. D. Shane (Lick 
Observatory Bulletin, No. 255) do not consider a para- 
bolic orbit to be included within the range of possible 
solutions, and so advocate a set of hyperbolic elements 
on which their ephemeris is based. The following are 
the elements they give :— 
l= 07 2500 
O56: U2 Az Tog: 
z =68° (00: 36'9" | 
The following ephemeris for the current week is 
based on the computations of Dr. G. van Biesbroeck : 
R.A. (true) Decl. (true) Mag. 
hewamMe GiS- Say a 
fitlysaOR ee ee Ghe2nste yicn 33, 52" Oana ie. 6:8 
1] ZAR ER aay TON IG 
18 27 14 SBA) 28526 - 6-7 
19 29 38 ss «= 34.47 4 
2 BA () . Godt B54 ke 
ar SOD eno abe at 
22 Be Mee Bh AS LOM ter. 6-6 
23 5 3042 = 307 2 16 
Attention may be directed to a communication to the 
Royal Academy of Belgium (Bulletin de la Classe des 
Sciences, 1914, No. 2, p. 101) by Dr. G. van Bies- 
broeck. In this the author discusses in detail the 
elements and positions of the comet, and gives an 
NO. 2323) VOlLeo3 i 
NATURE 
[ Juny 16, rQi4 
interesting chart of the positions of the comet in the 
sky (with the sun’s positions) extending from Septem- 
ber 1, 1913, to July 1, 1915. 
CLASSIFICATION OF NEBUL AND STAR CLUSTERS.— 
Those who have observed or photographed a large 
number of nebula and star clusters have no doubt 
experienced the difficulty of classifying them briefly 
without having to describe. each in detail. Nearly 
every astronomer who has had to deal with a large 
number of these objects has either adopted a previous 
system of nomenclature or has formed one of his own 
based partially on one previously selected. The time 
seems to have arrived when a universal method of 
nomenclature should be adopted, and M. G. 
Bigourdan, in the Comptes rendus (No. 26, June 20, 
1914, p. 251), discusses the whole question from this 
point of view. He reviews the systems of W. 
Herschel, J. Herschel, Schultz, Kobold, Wirtz, Max 
Wolf, Bailey, etc., and finally submits a scheme which 
while embodying the chief points and notations of 
previous classifications appears to be simple, brief, 
and comprehensive. This scheme should serve as a 
good basis for discussion, and, even if modified, M. 
Bigourdan will have done a good service by bringing 
this subject of classification to a head. 
Watts’s ‘‘ INDEX OF SPECTRA.’’—The “ Index of Spec- 
tra’? by Dr. W. Marshall Watts is a publication fami- 
liar to all spectroscopists, and completes and brings 
up to date in the forms of appendices the wave-length 
determinations of the elements. Appendix W, the 
second of a new series, has just made its appearance, 
and contains the spectra of chromium, cobalt, copper, 
dysprosium, erbium, europium, and fluorine, conclud- 
ing with additions and corrections to Appendix V. 
THE NAPIER TERCENTENARY. 
ee Napier tercentenary celebration, to be held in 
Edinburgh under the auspices of the Royal 
Society of Edinburgh, will open formally on the after- 
noon of Friday, July 24, when the Right Hon. 
Lord Moulton will deliver the inaugural address. The 
same evening the Lord Provost and magistrates will 
give a reception in honour of the event. On the after- 
noon of Saturday, the governors of Merchiston Castle 
School will entertain the members of the congress, 
who will thus have an opportunity of seeing the very 
room which John Napier occupied as his study. The 
divine service in St. Giles’ Cathedral on the afternoon 
of July 26, and the farewell reception given by the 
president and council of the Royal Society of Edin- 
burgh, form the remaining gatherings of a general 
nature. 
The other meetings will be essentially mathematical 
in character, and will be held on Saturday forenoon 
and on the greater part of Monday, in the University, 
the rooms of the mathematical department, and a 
number of other rooms and halls in the immediate 
vicinity being utilised for the purpose. 
The general arrangement of the programme is to 
devote Saturday forenoon to papers and discussions 
of an historical character. Dr. Glaisher, F.R.S., Prof. 
Cajori, Prof. Eugene Smith, and others are expected 
to take part. 
On the Monday the communications will refer mainly 
to the construction of mathematical tables and the 
methods of calculation. Prof. Andoyer, of Paris, Prof. 
Bauschinger, of Strassburg, Prof. d’Ocagne, of Paris, 
and M. Albert Quiquet, the secretary of the Actuarial 
Society of France, have all agreed to read papers on 
the subjects with which their names are identified, and 
well-known representatives from America and the 
United Kingdom will also be among the speakers. 
4 
