566 
revolutions per minute. The Fionia ran her official 
trials in Copenhagen Sound on December 18 with 
uniformly favourable results. 
Aw article in Engineering for January 9 directs 
attention to the waning supply of petroleum. Although 
a continually greater supply of petroleum is being 
placed on the market, this increased output is secured 
only by sinking more wells and boring to a greater 
depth, showing that the surface supply is becoming 
exhausted. At the beginning of this century the wells 
touched rroo ft., and to-day the average level of the 
oil may be placed at 2000 ft.—an ominously rapid 
rate of sinking. Dissatisfaction with existing methods 
and acute appreciation of the necessity for increased 
effort to keep up the yield have induced the United 
States Bureau of Mines to issue a warning, and to 
suggest improved methods of working. It cannot but 
be regarded as a happy augury that the authorities are 
alive to the extent of the drain made on the stores of 
oil, and of the necessity of husbanding the resources 
of the future. America, by reckless expenditure of her 
resources, has increased her annual output to 200 
million barrels, yet the demand for oil for special 
purposes has become so great that the rise in price is 
considerable—so great, indeed, that competition with 
coal for ordinary purposes has become impossible. 
The entire production of petroleum from all sources 
is only about one-fifth of the coal produced in England 
alone, and already schemes are on foot for obtaining 
a motor fuel from other sources. 
Tue issue of ‘‘ Willing’s Press: Guide” for 1914 is 
the forty-first to appear. The first 297 pages are 
devoted to an alphabetical list of newspapers and 
periodicals. Among other useful contents may be 
mentioned the classified list of the periodical Press of 
the United Kingdom according to the interest or 
subject dealt with, and the lists of metropolitan news- 
papers, the provincial Press, and American news- 
papers. 
OUR ASTRONOMICAL COLUMN. 
Comet 1913f (DeLavan).—This comet is gradually 
creeping up in north declination and getting brighter. 
The following is an ephemeris for intervals of four 
days :— 
Berlin Midnight. 
R.A. Dec. 
he tn ee 5 f 
Jan. 12 2 RSrAG wl toa 2 
16 2 SARSo) ew nO 136 
20 257230) +0 59 
24 3.23 +2 43 
28 3 5 40 +4 36 
Tue CrossLtey REFLECTOR AND NEBUL22.—Mr. Heber 
D. Curtis contributes to the Lick Observatory Bulle- 
tin, No. 248, a second list of nebulz and clusters 
photographed with the Crossley reflector, being a con- 
tinuation of that which appeared in Bulletin No. 219. 
It comprises photographs secured between September 
26, 1912, and November 1, 1913. The exposures were 
practically all of two hours’ duration, but the author 
states that longer exposures and counts limited to a 
radius of 15’ from the optical axis might easily show 
larger number of nebula per square degree. The 
NO. 2307, VOL. 92| 
NATURE 
[JANUARY 15, I914 
present list comprises descriptions of 109 nebulz and 
clusters, and many uncatalogued nebula which pre- 
sent features of interest are included. The list is 
striking in that on some plates such a large number 
of nebula was photographed. Thus under N.G.C. 20 
it is stated that there are forty-one nebule on this 
plate; under N.G.C. 68 eighty-seven were counted in 
an area of 45’x55'; on other plates we find 30, 31, 37, 
31, 36, 28, 47, 69, 28, 17, nebulz recorded. 
Garactic Coorprinates.—The South African Journal 
of Science for November last (vol. x., No. 3) contains 
a communication from Mr. R. T. A. Innes, advocat- 
ing the use of galactic coordinates for star positions. 
The adoption of fixed instead of moving coordinates 
is an object much to be desired, and it woufd eliminate 
a great amount of labour if such a system could be 
adopted. Regarding the adoption of the galactic 
plane as a point of departure for measurement the 
galaxy is so irregular that estimates of the great circle 
which most truly represents it do not agree among 
themselves. Mr. Innes thinks, however, that such 
criticism is superficial. Mr. Crommelin (Knowledge, 
january) points out that both the galactic circle and 
the suggested starting point, the longitude of the sun’s 
apex, are arbitrary, and that ‘it would be ex- 
ceedingly difficult to get the astronomers of all nations 
to agree on points of this kind.” Further, he suggests 
that it is likely that for a long time to come meridian 
instruments will be the chief means of obtaining the 
places of at least the brighter stars, so that the 
R.A.’s and declinations will still have to be found. 
Mr. Innes’s paper is nevertheless an interesting and 
suggestive contribution. 
Tue Arc Spectrum oF IJron.—Lick Observatory 
Bulletin, No. 247, is devoted to an investigation on the 
arc spectrum of iron carried out by Mr. Keivin Burns 
at the Physical Institute at Bonn at the suggestion 
of Prof. Kayser. The object was to measure with 
reasonable accuracy all the lines of the are spectrum 
of iron which can be readily photographed. It was 
proposed to measure the stronger lines on four plates 
each and the fainter on two plates. This programme 
has been completed for the region 3206-7800 A, but 
for various reasons shorter and longer wave-lengths 
than the above are excluded. The apparatus used was 
a Rowland concave grating mounted according to 
Abney’s method—that is, the slit is the only movable 
part of the apparatus. The author describes the plates 
used, the standards employed, and the method of 
measurement and reduction, and accompanies his com- 
munications with the long list of wave-lengths derived. 
In comparing his results with those of Goos, he finds 
that the differences, Burns minus Goos, are usually 
less than 0-004 A, limiting the comparison to lines 
about equal in intensity to the standards. Other lines, 
he says, do not agree so well. Referring to the Mount 
Wilson measures, he writes :—‘‘My measures are in 
good agreement with the values of St. John and Ware, 
in the case of lines for which these observers find the 
same wave-length on Mount Wilson as in Pasadena. 
In cases where they find a difference between the 
mountain- and sea-level, my measures are in excellent 
agreement with the wave-lengths found on the moun- 
tain, although my observations were made at sea- 
level.” The author again directs attention to the 
systematic differences of wave-lengths or displacements 
with regard to the lines of impurities, a subject 
referred to in this column on August 7 of last year 
(vol xci., p. 592). He here asks the question: ‘‘ Will 
the wave-length of a line in the carbon arc be different 
from the wave-length of the same line at the same 
pressure in the iron arc?"’ The answer may not be so 
easy to give correctly as it appears to be. 
