462 

search Station, Long Ashton, Bristol, has now directed 
attention to the considerable amount of waste material 
from the saw mills, and has made analyses showing 
that this also yields a residue containing from 6 to 
10 per cent. of potash (K,O). Mr. Gimmingham 
points out that the wood scraps, sawdust, and shav- 
ings from planing machines, etc., are produced in 
enormous quantities in every sawmill in the country. 
Some of this material, and notably the sawdust, is 
saleable in certain localities, but the great bulk of 
it is available for conversion into ash. In many cases 
this is already done; the wood is used as fuel, either 
alone or mixed with coal, and the ash is then readily 
obtained. It is interesting to note that in these cases 
the flue dust also contains a considerable proportion 
of potash, in one case as much as 9g per cent. being 
found. From the fertiliser point of view the ad- 
mixture of coal with the wood is a disadvantage, and 
in view of the fact that the pure ash is worth anything 
from 25s. to 50s. per ton as fertiliser, it is well worth 
considering whether greater economy could not on 
the whole be effected by leaving out the coal and using 
wood waste only for fuel. 
OUR ASTRONOMICAL COLUMN. 
Comet Nores.—An ephemeris of comet 1915a 
(Mellish) is published in the Astronomische Nachrich- 
ten, No. 4802, being a continuation of that published 
in No. 4801. It gives the magnitude as 5-5 on July 2, 
the brilliancy decreasing steadily afterwards. The 
comet will be a conspicuous object in July for southern 
observers, but its large southern declination during 
that month renders it unfavourable for observation 
in higher latitudes. Fortunately the southern declina- 
tion will rapidly decrease, and the comet will be again 
visible in these latitudes. Dr. Crommelin, writing in 
Knowledge for June, hopes that it may still be a 
naked-eye object. The orbit, he says, “shows a slight 
resemblance to that of comet 1748 1I., which was seen 
only on May 19, 20, and 22, in 1748, so that the elements 
are not very well known. Identity of the two comets 
is perhaps just possible, but not probable.” A con- 
tinuation of the ephemeris of the periodic comet 
Tempel 2 is also printed in Astronomische Nachrichten 
No. 4802, giving positions down to the end of next 
August. 
Orsits oF EcuipsinG Bixartes.—No. 3 of the Con- 
tributions from the Princeton University Observatory 
contains an important study of the orbits of eclipsing 
binaries by Dr. Harlow Shapley. It may be remem- 
bered that it was in 1912 that new methods were intro- 
duced for the computation of the orbit of an eclipsing 
binary, and these have permitted the rapid develop- 
ment of this phase of double-star astronomy. It has 
now become possible, as Dr. Shapley remarks, to 
derive as much information concerning binary systems 
in general, and their bearing on stellar evolution, 
from the orbits of eclipsing variables as from spectro- 
scopic binaries or visual doubles. These new methods 
and their development are due to Prof. Russell and 
Dr. Shapley, and the present publication gives briefly 
the theory underlying the methods, and exhibits in 
some detail how these methods are employed in dealing 
with the considerable variety of problems that arise. 
A preliminary report in 1912 dealt with the orbits 
of forty-four stars, and later the results for eighty- 
seven stars were published. The present discussion 
represents the complete investigation of practically all 
NO. 2382, VOL. 95] 
NATURE 


[JUNE 24, 1915 
the material available up to the present time, and 
contains in final form the treatment of ninety eclipsing 
variables. Dr. Shapley for the last two and a half 
years has been using the equipment of the Princeton 
Observatory to add to the material, and has made 
about 10,000 light measures with the polarising photo- 
meter. This has been done to obtain complete light 
curves of interesting stars, to fill up gaps in published 
series of observations, and to correct existing light 
curves. In the arrangement of the text the author 
has, as far as possible, kept the tabular matter separate 
and brought this together in the appendix. On p. 124 
he summarises some suggested investigations on 
eclipsing binaries, and points out lines along which 
further investigations are desirable and could be 
accomplished without serious difficulty. 
THE VARIATION OF LATITUDE DURING 1914:0-1915:0.— 
Prof. Albrecht publishes, in the Astronomische Nach- 
richten, No. 4802, provisional results of the inter- 
national service for the determination of the variations 
of latitude. Fortunately, the war has in no way 
disturbed the observations at the six stations, so that 
the determination of the path of the pole has been 
continued as on former occasions. The communica- 
tion is accompanied by the usual chart showing the 
track of the pole for the period 1909-0 to 1915-0, indi-- 
cating an increase of amplitude of swing since the 
latter end of the year 1913. 
Tue Society For Practica, ASTRONOMy.—The April- 
May number of the Monthly Register of the Society 
for Practical Astronomy, Chicago, has just come 
to hand. While the astronomical observations pub- 
lished in it are very brief, dealing only with some 
observations of comets and a short report on the 
planetary and lunar section, attention is directed to 
the need of a new section which should have for its 
object the furthering, in all possible ways, of the 
teaching of elementary astronomy according to modern 
methods. The writer of this appeal, Dr. Mary Byrd, 
formerly director of Smith College Observatory, refers 
to a circular letter issued some years ago by the 
American Astronomical Society, in which it was 
stated :—‘‘ The society considered the deplorable ignor- 
ance of persons, otherwise intelligent, in regard to 
everyday phenomena of the sky, and the fact that 
astronomy lags behind the other sciences in adopting 
the modern method of laboratory worl: by the student.”’ 
As a move in the direction of remedying this defect 
the author advocates a scheme of organised effort to 
make elementary astronomy a practical study, and 
calls on the great body of amateurs in America to 
enlist themselves in the new movement. 
AIMING WITH THE RIFLE. 
S° many people are now learning to shoot with 
the rifle that it is profitable to consider some of 
the difficulties they are likely to meet with. These 
difficulties become greater as the age of the learner 
increases, and they may be minimised or accentuated 
by the lighting of the range at which the learner 
practises. A discussion of the lighting of rifle ranges, 
which took place at the monthly meeting of the 
Illuminating Engineering Society on May 18, shows 
very clearly that the existing conditions place artificial 
obstacles in the way of the learner; and it may fairly 
be contended that these obstacles never would have 
arisen, and the path of the learner would have been 
considerably smoothed, if certain optical principles had 
been recognised and utilised. Mr. A. P. Trotter, who 
opened the discussion, gave a very clear account of 
the difficulties encountered by a man of middle age 
when he attempts to shoot at one of the many indoor 


