June 17, 1915] 
NATURE 
437 

not admit of any great accuracy, some ionisation 
method appears preferable, such as is employed in 
Villard’s X-ray counter, in which an electroscope is 
discharged a number of times. It then remains to 
measure the “hardness” of the rays, or their pene- 
trating power, and this may be done by Benoist’s 
‘“‘radiochromometer,”’ consisting of a ring of alumin- 
ium strips of twelve different thicknesses. There is 
still, however, much room for improved methods of 
dosage. 
Mr. James Keir directs attention in the Engineer 
for June rr to the use of cast-iron shells of fairly 
large calibre by the Germans. Mr. Keith suggests 
that, whether or not there be any particular reason 
for our keeping to expensive steel shells, there could 
surely be no harm in our haying cast-iron ones as 
well to fill up the gaps, and so enable innumerable 
shells to be at the service of the armies of the Allies. 
The matter is taken up by our contemporary in a 
leading article, and the objections to the course sug- 
gested by Mr. Keith are discussed fully. In shrapnel 
cast-iron shells, the number of bullets is reduced be- 
cause the walls of the shell must be made much 
thicker. In high-explosive shells there is such danger 
of a cast-iron shell developing cracks during manu- 
facture that high explosives cannot safely be used in 
them. Further, projectiles must be perfectly in 
balance; the walls must be of uniform thickness all 
round, and must be of homogeneous material, Other- 
wise accuracy in shooting would be destroyed. Lastly, 
the methods of manufacture of steel shell have been so 
developed that such shell can actually be turned out 
more quickly than those of cast-iron of equal trust- 
worthiness an@ accuracy. An 18-pounder shell can be 
completely machined from the bar in about forty 
minutes. The Engineer suggests that the use of cast- 
iron by the Germans indicates that they are finding 
their supplies of modern projectiles not inexhaustible 
under the tremendous drain that is being put upon 
them. : 
Messrs. LONGMANS AND Co. announce for early pub- 
lication “The House Fly : a Slayer of Men,” by F. W. 
Fitzsimons, director of the Port Elizabeth Museum. 
The volume will be illustrated. The author has 
worked for several years at the destruction of the 
house-fly in South Africa. 

OUR ASTRONOMICAL COLUMN. 
BEHAVIOUR OF SPECTRUM LINES OF THE SAME SERIES. 
—The lines in a series are generally assumed to 
behave alike (omitting reversals), even under varying 
experimental conditions. In fact, their sharpness, 
diffuseness, or direction of unsymmetrical widening 
have been used as criteria in the detection of series 
relationships. Thus if the strong lines of a series 
were unsymmetrically widened towards the red the 
remaining lines of the series would be expected to be 
widened in the same direction. This, however, is not 
the case, and an investigation bearing on these points 
is communicated by Dr. Royds to the forty-third Bul- 
letin of the Kodaikanal Observatory (see also the 
Astrophysical Journal, March, vol. xli., No. 2, p. 155 
In the case of the barium lines he finds that all the 
first members of the first subordinate series are dis- 
NO. 2381, VOL. 95] 

placed to the red, and the second members to the 
violet. In the case of the calcium series he finds 
this not so extreme a case as that of barium, but still 
a noteworthy exception to the general run of series. 
The strontium series, on the other hand, is stated to 
be quite normal if the infra-red lines the character 
of which is unknown are excepted. Dr. Royds directs 
attention to the whole question of the relationship 
between pressure shifts and series, since the pressure 
shift may even be in opposite directions for lines of 
the same series. He points out, further, the import- 
ance of isolating the pressure effect from the density 
effect, the elimination of the latter in order to obtain 
true pressure shifts being ‘‘one of the most pressing 
problems for those interested in the displacements in 
the sun’s spectrum.” 
Tue FisHer, Pork Country, Minnesota, METEORITE. 
—In the American Geologist for December, 1894, brief 
mention was made of the finding near Fisher, Poll 
County, Minnesota, of a meteoric stone weighing nine 
and a half pounds. This stone, the first found within 
the State limits, was assumed to be a representative 
of a reported fall which took place on the oth of the 
preceding April. In a subsequent number of the 
Geologist a petrographic description of the stone was 
begun by Prof. N. H. Winchell, but this was neither 
completed nor was a satisfactory chemical analysis 
made. In view of these facts and also because more 
parts have been subsequently found, a complete review 
of the whole matter has been undertaken by Prof. 
G. P. Merrill, and the results are published in No. 2084 
Proceedings of the United States National Museum 
(vol. xlviii., pp. 503-6, May, 1915). It seems that speci- 
mens of this fall are distributed in eight different 
collections, the four largest portions being in institu- 
tions in Minneapolis, Washington, New York, and 
Hamburg; the total weight of all the known portions 
amounts to 9900 grams. The author has been offered 
facilities for examining and taking samples for the 
purposes of identification and chemical analysis, and in 
this paper he publishes the results of his inquiry. 
Following Brezina’s classification he places the stone 
in the group of intermediate chrondites Ci, or perhaps 
Cia, as one cut surface shows a small thread-lilke black 
vein. 
Tue Nantucket Marta MircHert Assocration.—In 
the thirteenth annual report of the Nantucket Maria 
Mitchell Association, an account is given of the astro- 
nomical work accomplished during the past year. 
This association completed in 1911 the Astronomical 
Fellowship Endowment Fund, and the first fellow 
was appointed in the following year; the second 
has just been nominated. This fellowship enables 
the holder to avail herself of the entire year 
for study and research in an observatory of her own 
selection. Miss Annie J. Cannon, the chairman of 
this special committee, describes briefly the work of 
the association with the new 73 in. photographic 
telescope. After the adjustments were completed 
numerous photographs were taken, chief of which 
were of the minor planet Eros. These plates are 
now being measured by the first fellow, Miss Har- 
wood, at the Harvard Observatory, together with the 
plates of the same asteroid taken at that observatory. 
The chief research will be the photographing of each 
asteroid once a month for as long a period as possible, 
the selected objects being those for which the 
copemeris at opposition is given in the Berlin Jahr- 
uch. 
RECENT BULLETINS OF THE ASTRONOMICAL SOCIETY OF 
FRraNcE.—The April and May numbers of the valuable 
Bulletin of the Astronomical Society of France have 
; come to hand in spite of the difficulties under which 
