384 
NALORE 
PJUNE' 13, done 
jacket surrounding the exhaust pipe. To ensure 
rapid cooling, the exhaust gases are led through 
Serve tubes. The water jacket is formed by the space 
between the Serve tube and an external tube of 
slightly greater diameter; the annular space is kept 
small in order to obtain a high velocity of flow in 
the circulating water. Thermometers are inserted in 
suitably packed pockets. The whole apparatus is 
exceedingly simple and inexpensive to construct, 
being built up of standard pipe fittings, and should 
prove a useful addition to the testing appliances of 
an engineering laboratory or of a works’ test plate; 
the otherwise troublesome operation of determining 
the heat wasted in the exhaust gases may be easily 
performed by its use. 
We learn from The Engineer for June 7 that rapid 
progress is being made with the leviathan dock at 
Liverpool, and that it is hoped to complete the work 
in the summer of 1913. This dock is 1020 ft. long 
—nearly 140 ft. longer than the Olympic—and has an 
entrance 120 ft. wide. The structure of the dock is 
to be such that it will be available when required as 
a graving dock for overhauling and repairing the 
largest steamers likely to be met with for some years. 
The entrance will be provided with a sliding caisson 
having a clapping face on each side, so as to main- 
tain the water in the dock or exclude it therefrom 
according to the duty required. The caisson is 134 ft. 
in width. The dock walls are 60 ft. high, and are 
practically complete. For emptying the dock, five 
sets of centrifugal pumps with Diesel engines will be 
installed. These will be capable of emptying the 
contents of the dock, amounting to about seven 
million cubic feet of water, in two and a half hours. 
SEVERAL new editions of scientific works have been 
received recently. These include a second edition of 
Prof. A. G. Webster’s ‘‘The Dynamics of Particles 
and of Rigid, Elastic, and Fluid Bodies,”’ published 
by Mr. B. G. Teubner, of Leipzig, and Messrs. 
Williams and Norgate, in London, at the price of 
14s. net. This edition is substantially identical with 
the first, except that a few errors have been corrected. 
—A second edition of Prof. E. C. C. Baly’s ‘ Spectro- 
scopy’ has been issued by Messrs. Longmans, Green 
and Co., at the price of 12s. 6d. In it Prof. Baly 
has given a résumé of the salient points of the more 
modern work, and has provided useful lists of refer- ° 
ences.—Messrs. Hazell, Watson and Viney, Ltd., have 
issued a ninth edition of ‘‘The Dictionary of Photo- 
graphy,’ by Mr. E. J. Wall, which has been edited 
by Mr. F. J. Mortimer. The book has been com- 
pletely revised and brought up to date, and nearly a 
hundred pages of new matter have been added. The 
price of the new edition is 7s. 6d. net.—A sixth edition 
of Miss M. N. Oxford’s ‘‘ Handbook of Nursing ”’ has 
been published by Messrs. Methuen and Co., Ltd., 
at the price of 3s. 6d. net. This work has been 
entirely revised, and in the work of revision the 
author has had considerable expert assistance.—From 
’ the same publishers we have received a copy of the 
ninth edition of Sir Oliver Lodge’s ‘‘Man and the 
Universe,” which can now be obtained at ts. net. 
NO. 2224, VOL. 89] 
! 
OUR ASTRONOMICAL COLUMN. 
Nova Geminorum No. 2.—The more salient 
features of two series of spectrograms taken at the 
Pulkowa Observatory (March 15-18 and March 25 
and 26) are described by Dr. Tikhoff in No. 2, vol. v., 
of the Mitteilungen of that observatory. The scale 
was small, 6°3 mm. from H8 to He, but the negatives 
clearly disclose the extraordinary changes which took 
place in the spectrum of the nova. By employing 
different plates and filters, Dr. Tikhoff secured nega- 
tives giving the whole spectrum from Ha to Hy, and 
he states that on March 15 the characteristic feature 
was a series of intense absorption lines, both broad 
and narrow, the bright lines being but little brighter 
than the intense continuous spectrum. He classifies 
the spectrum as lying between types F and G. On 
March 16 the continuous spectrum generally had 
diminished considerably in brightness, except in the 
ultra-violet, where it was brighter and extended to 
about A3600; the absorption bands of hydrogen were 
scarcely visible on this date, although H and K were 
very strong and the bright bands of hydrogen very 
intense. The striking features on March 25 were 
the reappearance of the absorption bands and the 
strong continuous spectrum. 
During the two periods of observation two 
analogous series of changes occurred in the spectrum, 
such as might be produced, Dr. Tikhoff imagines, 
by the shattering of successive absorbing envelopes 
by fresh outbreaks of incandescent gases from the 
central mass. 
Prof. Belopolsky, in the same Mitteilungen, gives, 
in great detail, the measures of the structure of the 
various H, Ca, He, and N (?) lines, from which he 
deduces the radial velocities and possible physical 
conditions of the emitting masses. 
THe Minor Pranet 1911 MT.—From a note in 
The Observatory (No. 449, p. 243) we learn that the 
elements for the orbit of the exceedingly interesting 
asteroid 1911 MT., calculated by Messrs Haynes 
and Pitman, are, as shown by the observations, fairly 
accurate. The planet has a period of about 2°6 years, 
while its perihelion distance is about the same, 1°15, 
as that of Eros, but the eccentricity of the orbit is 
nearly twice as great. The next opposition will take 
place in March, 1913, but the planet’s magnitude 
will then be 17 or 18; most of the oppositions take 
place when the planet is near aphelion, and are 
therefore unfavourable for observation. According to 
amended elements published by Prof. Franz, in 
No. 4575 of the Astronomische Nachrichten, the orbit 
is like that of Eros, but the planet approaches even 
nearer the earth than does the famous object dis- 
covered by de Witt. 
THE SPECTRUM OF P CyGni.—Discovered by Janson 
in 1600 and observed as a third-magnitude star, by 
Cassini, for a short period in 1655, the star P Cygni 
has for more than 230 years remained at nearly 
constant magnitude, 50, and its spectrum still re- 
quires adequate explanation. Prof. Frost, dealing 
with it in a paper published in No. 4, vol. xxxv., of 
The Astrophystcal Journal, offers some interesting 
points for consideration. 
Among other things he finds that in recent years 
the spectrum has remained practically constant, that 
the apparently large displacements of the dark com- 
panions to the bright lines are spurious, being pro- 
duced. by the obscuration of their less refrangible 
portions by the bright lines, and that there is a 
difference of 70 kms. between the radial velocities of 
the dark- and bright-line systems. The lines of H, 
He, O, and N are represented both as emission and 
absorption, while Ca and Si present dark lines only; 
