Marcu 4, 1915] 
NATURE 
17 

and avoiding any tendency to buckle the train in the 
middle due to excessive pushing forces in the rear, 
Tue forthcoming books of Messrs. John Wiley and 
Sons, Inc. (New York), include :—Elementary Chem- 
ical Microscopy, E. M. Chamot; The Examination of 
Hydrocarbon Oils and of Saponifiable Fats, D. Holde, 
translated by E. Mueller; Text-Bools of Geology, L. V. 
Pirsson and C. Schuchert; A Meteorological Treatise 
on the Circulation and Radiation in the Atmospheres 
of the Earth and of the Sun, F. H. Bigelow; Manual 
for Health Officers, J. S. MacNutt; Constant-Voltage 
Transmission, H. B. Dwight; Field Book of Railroad 
Engineering, W. G. Raymond; Materials of Construc- 
tion: their Manufacture, Properties and Uses, A. P. 
Mills; Steam Power, C. F. Hirshfeld- and T. C. 
Ulbricht; The Railroad Taper: the Theory and Appli- 
cation of a Compound Transition Curve based upon 
30-foot Chords, L. Perkins; Working Data for Irriga- 
tion Engineers, E. A. Moritz; A Shop Mathematics 
for Machinists, R. W. Burnham; Interpolated Six- 
Place Tables, H. W. Marsh; Masonry, M. A. Howe; 
Plain and Reinforced Concrete Arches, J. Melan, 
translated by D. B. Steinman. 

OUR ASTRONOMICAL COLUMN. 
Tue Return or Mercatr’s Comet?—In Nature of 
February 25 reference was made to a telegram re- 
ceived by Prof. Stromgren relative to the discovery 
of an object by Miss Leavitt believed to be Metcalf’s 
comet. The Morning Post of February 23 published 
the following paragraph relative to this discovery : 
“A telegram from Prof. Pickering has just been 
received stating that the object reported as Comet 
Metcalf turns out to be a minor planet. This must 
be a disappointment to Miss Leavitt, but it accounts 
for the failure of astronomers to find the comet when 
better placed. The question of priority of discovery, 
as evidenced by the Southern comet of last year, which 
was discovered independently at Johannesburg, 
Arequipa, and Christchurch, New Zealand, on the 
very same day, has been already responsible for 
premature publication. Prof. Pickering is, however, 
generally prepared to take the risk and is sometimes 
fully justified.”’ 
THE CANADIAN 72-INCH’ REFLECTING TELESCOPE.— 
Dr. J. S. Plaskett communicates some very satisfactory 
information about the large Canadian mirror which 
is in process of being worked up. (Journal of the 
Royal Astronomical Society of Canada, Noy.—Dec., 
1914.) The mirror is actually 732 inches in diameter 
and 133 inches thick, weighing 4962 pounds, or a 
little more than two tons. An excellent idea of the size 
of this vast piece of glass will be gathered from the 
illustration accompanying Dr. Plaskett’s note, showing 
the dise with Dr. John Brashear sitting beside it. 
Already the edge has been ground, the labour occupy- 
ing three weeks, and the more delicate and dangerous 
work of drilling the central hole has been satisfactorily 
completed. The latter involved first boring a hole of 
9 inches diameter, then enlarging it to 10 inches, and 
finally smoothing and squaring it up and bevelling 
off the top edge. The next procedure is the figuring 
ot the upper and lower surfaces to make each plane 
in order to choose which surface is the more suitable 
for shaping into parabolic form. It is satisfactory to 
read that ‘‘the more the disc is examined the better 
it seems to be, and hopes are high that it will prove 
a great success.” 
NO. 2366, VOL. 95] 
ANOMALOUS DISPERSION IN THE SUN.—No, 93 of the 
Contributions from the Mount Wilson Observatory 
contains a communication from Mr. Charles E. St. 
John, entitled ** Anomalous Dispersion in the Sun in 
the Light of Observations.” Mr. St. John first 
directs attention to recent publications by Prof. Julius, 
who has considered the displacements of the Fraun- 
hofer lines at the centre and limb edges of eccentric- 
ally located sun-spots from the point of view of his 
theory of anomalous dispersion. In these Prof. 
Julius has set forth ‘‘a new deduction from the theory 
of anomalous dispersion—the ‘tmutual influence” of 
the Fraunhofer lines upon each other; in particular, 
that a weak line on the violet side of, and near to, a 
stronger line is displaced less, but if on the red side 
more, than the average amount.’’ The above deduc- 
tion affords Mr. St. John, as he says, an opportunity 
of making a quantitative test of the réle played by 
anomalous dispersion in the solar atmosphere, and 
this he does in the present paper. It may be re- 
marked that Prof. Julius used the data published by 
Mr. St. John in his paper, “ Radial Motion in Sun- 
spots.”’ In the present discussion, which covers more 
than forty pages, it is impossible to refer even briefly 
to any of the details here stated. Mr. St. John sums 
up in eleven paragraphs the results of his investiga- 
tion, and the reader must refer to the article itself for 
further information. The general result may, how- 
ever, be expressed by reproducing the last paragraph 
of the summary. ‘The general conclusion from this 
review of solar observations is that the deductions 
from the anomalous dispersion theory which are sus- 
ceptible of definite and quantitative tests are not sup- 
ported by the observational data, and that observa- 
tions are outstanding which have not yet been ex- 
plained by the theory.” 
GREAT DETONATING FIREBALL IN SouTH AFRICA.— 
Some of the South African newspapers just received 
give particulars of a fireball which appeared nearly 
over Cradock and Queenstown on January 9g last at 
1.20 a.m. It vividly illuminated the heavens for 
several seconds, and was followed shortly after by a 
series of loud explosions. 
The meteor evidently came from the N.N.W., pass- 
ing between Cradock and Queenstown, and _ finally 
disappearing to the S.E. of the former place at a 
distance of about 24 miles, but the exact figures are 
doubtful. The estimated interval between the flash 
and the detonation was variously given by different 
persons at Cradock between 30 seconds and 3 minutes. 
The meteor may have fallen to the earth in the region 
S.E. of Cradock, and it is to be hoped that a thorough 
search has been instituted for the object. Its flight 
appears to have been directed from the position of the 
radiant of the January meteoric shower from 
Quadrans, the maximum display from which is 
usually developed on January 3. But the shower is 
certainly prolonged until January 9. The meteor, 
however, more probably owed its origin to a radiant 
in the constellation Draco. 
The recent meteor startled a large number of 
persons by its loud detonation. Houses are said to 
have been shaken, and the visitation was ascribed 
by many people to an earthquake. The real path 
cannot be satisfactorily computed from the observa- 
tions, which are not of a suitably exact character. 
The period from January g to 14 is notably rich 
in fireballs, and it merits further investigation. There 
are evidently a number of radiant points active at 
this epoch, and among those best pronounced will 
be found positions at 120°+0°, 148°— 12°, 230°+52°,. 
i and 332°+ 36°. 

