JUNE 25, 1914] 
drainage of Lake Mareotis at Mex, near Alexandria. 
When completed, there will be eighteen pumps, each 
capable of delivering 100,000,000 gallons a day 
through a lift of 20 ft. The present order comprises 
the first ten pumps, together with the necessary gas 
producers, Venturi meters, etc. The great size of 
the pumps may be judged from the fact that their 
capacity will be between two and three times that of 
the pumps installed at the Chingford Reservoir. The 
combustion chambers will have a maximum internal 
diameter of 8 ft. 8in., and a height of 14 ft. approxi- 
mately. Each water valve box will be 8 ft. 8 in. in 
diameter, and 7 ft. high, and will have 100 valves of 
the hinged type, specially designed to enable any 
valve to close upon an obstruction without throwing 
undue stress upon the hinges. On the next stroke, 
when the obstruction has been removed by the rush 
of water, the valve will readjust its position auto- 
matically and close fairly upon its seat. 
Tue accidental subsidences which occurred in Paris 
a few days ago on one of the Paris Metropolitan lines 
now in course of completion form the subject of an 
article in Engineering for June 19. The driving of 
the new underground line appears to have been the 
immediate cause of the catastrophe. The existing 
masonry sewers seem to have been shored up over the 
tunnel driven to take the line; they appear to have 
broken down at parts during the violent storm 
of June 15, and the water, by flowing into 
the tunnel, led to undermining and to. the 
caving-in of the tunnel arch by carrying away 
the earth and stone on which the arch rested 
temporarily, and aiso by carrying away at intervals 
the masonry walls which formed its final support. It 
is quite evident that the excavation work, which the 
construction of the new lines involves, is surrounded 
with most serious difficulties, carried out as it is in the 
very soft earth which constitutes the subsoil of Paris, 
amongst a most complicated network of sewers and 
pipes, and very frequently through bodies of under- 
ground water. It is too early to draw conclusions 
from the disaster, but one point would seem to stand 
out clearly, and this is to the effect that no precaution 
and no reasonable amount of timbering should be 
deemed superfluous when driving a large network of 
tunnels in a treacherous subsoil like that of Paris. 
OUR ASTRONOMICAL COLUMN. 
Comet Notes.—Zlatinsky’s comet (1914b) is gradu- 
ally becoming fainter and getting further south, but 
the following ephemeris, calculated by Prof. Schwass- 
man (Astronomische Nachrichten, No. 4739) of Berge- 
dorf, will permit of it being followed with larger 
instruments :— 
ann (true) Dec. (true) Mag. 
June 24 0 24. .10;2) eae ~9 3 Is sae POO 
25 25499 «=. 9 36 3 
26 27 20:2) 0), a. igen a) 35 
27, 28- 47-6 en Oe aTS P21) 9:1 
28 GO. 12-20 Siew eee aa 
29 31 344 --- IT 34 42 
30 32 SA 4 nee, woe ear 
FulyoueT 9 34 12-2 i eHAO hs. G4 
NO.—23 30," VOL. 03) 
NATURE 
437 
The comet discovered by Kritzinger (1914a) is @ 
circumpolar object due to its large positive declina- 
tion. An ephemeris is published in Astronomische 
Nachrichten, No. 4739, by M. P. Chofardet, and the 
following are the positions for the current week :— 
R.A. Dec. 
Ire, WIDisw-Ss 5 i 
femegen tn 22000 Gol) to aag 
27 Sesore? Fee te Oo) 
29 Tog 2) 2.2 4 ASG 
d UG Sas ote eee LA E2 cba te BAL AR 
Ae Mae) ms ie aay . +44 36-7 
Elements and ephemeris for Delavan’s comet (1913f)) 
are also given in the same number of the Astro- 
nomische Nachrichten. This comet is now about the 
gth magnitude, and is brightening up considerably, 
but cannot yet be observed owing to its nearness to 
the sun. It will be picked up, however, somewhere 
about the latter end of July. 
Larce TeLescopes.—Mr H. P. Hollis publishes 
(Observatory, June) a very interesting list of large 
refractors and reflectors, either under construction or 
already set up -in observatories. In the case of re- 
fractors, the lower limit of aperture of the object glass 
is taken as 20 in., and the same limit is also taken 
in the case of the reflecting telescopes. Of the thirty- 
eight refractors about which details are given, the 
largest objective is that of 49-2 in. made for the 
Paris Exhibition of 1900. As this is out of use, the 
largest working objective is that of the Yerkes Ob- 
servatory at Wisconsin, U.S.A. Of the refractors. 
under construction the following may be mentioned :— 
A 32-in. for the Nicolaieff Observatory, Russia; a 
26-in. for the Union Observatory, Johannesburg ; three 
24-in. for the following observatories: Argentine 
National Observatory, Cordoba, Chili National Ob- 
servatory, Santiago, and the Detroit Observatory, 
Michigan, U.S.A., and a 20-in. for the Chabot Ob- 
servatory, Oakland, California. The Earl of Ross’s 
72-in. reflector holds the field for the largest reflector 
(metallic speculum), while Dr. Common’s 60-in. (silver 
on glass), now at the Harvard Observatory, U.S.A., 
comes second. Of those under construction, two 
giants are in hand, namely, one of too in. for the 
Mount Wilson Solar Observatory, and one of 72 in. 
for the Dominion Observatory, Canada. Others under 
construction are a 4o-in. for the Simeis Observatory, 
Crimea, and two of 30 in., one for the Helwan Ob- 
servatory, Egypt, and the other for Mr. D’Esterre’s 
observatory, Surrey, England. It is interesting to 
note that the number of instruments in each list is 
about the same, namely, thirty-eight refractors and 
forty reflectors. 
A PLaneTtT BeyonD NepruNe.—Mr. H. E. Lau con- 
tributes to the June number of L’Astronomie a short 
account of his researches on the perturbations of Nep- 
tune and Uranus leading him to suggest a case for a 
planet beyond Neptune. He produces some interest- 
ing and suggestive curves showing the apparent irre- 
gularities of the movement of Uranus according to 
the errors of the tables after Newcomb, Gaillot, and 
himself. As regards the conclusions he draws at the 
end of his article he states that they should only be 
accepted with extreme reserve. The researches made 
by M. Gaillot and himself, ‘‘établissent seulement 
que l’hypothese des deux planétes transneptuniennes 
n’est pas en conflit avec les faits observés de sorte 
qu’il peut exister deux ou plusieurs grosses planétes 
au dela des limites actuelles du systéme solaire.” 
RECENT Procress or AstRoNomy.—In the Annuaire 
de V’Observatoire Royal de Belgique for 1914 Prof. 
