AUGUST 20, 1914] 
air through which an electric current is passing, and 
measurements of the change of refractive index of air 
with temperature are further applications. Finally the 
author deals with the measurement of the deflection of 
an electrometer needle by interference, and shows that 
such an instrument will measure a few millionths of a 
volt. 
In connection with the development ot the Langley 
Aerodynamical Laboratory of the Smithsonian Insti- 
tution, the purpose of which, it will be remembered, 
is primarily to plan and conduct such theoretical and 
experimental investigations, tests, and reports as may 
serve to increase the safety and efficiency of aerial 
locomotion for commercial advance, national defence, 
and the welfare of man, a visit was paid a short time 
ago to various kindred institutions in Europe by 
Dr. A. F. Zahm, the recorder of the Langley 
Laboratory, accompanied by Mr. J. C. Hunsaker, of 
the U.S. Navy. The tour of inspection included the 
British, French, and German laboratories; also many 
of the aerodromes, aircraft factories, and aeronautical 
libraries, the object being the study of the latest 
developments in instruments, methods, and resources 
used and contemplated for the prosecution of scienti- 
fic aeronautical investigations. The results of their 
observations are embcdied in No. 2273 of the Smith- 
sonian Miscellaneous Collections. 
BULLETIN No. 8 of the Mellon Institute of Indus- 
trial Research deals with some engineering phases 
of Pittsburg’s smoke problem. In this district more 
bituminous coal is used than in any other district of 
like size in the world. The coal found in the neigh- 
bourhood of Pittsburg is very plentiful, cheap, and 
rich in volatile matter. Further, the many hills and 
valleys and the frequent fogs hold the smoke long 
after it would have been carried away in another 
locality having a more regular topography. The soot- 
fall for the twelve months ending April, 1913, at the 
various observation stations in Pittsburg ranges from 
595 to 1950 tons per square mile. Pittsburg learned 
the appearance of a clean city during the brief period 
in which natural gas was largely empioyed; since 
1895 the use of coal has been general again. The 
local authorities have made attempts since 1893 to get 
rid of smoke production at the pumping stations, but 
with little success; the Mayor reported in 1913 that 
one of the worst offenders against the smoke ordin- 
ance is the city of Pittsburg at the Northside light 
plant and the Brilliant pumping station. Of special 
interest is a series of photographs showing two views 
of each locality, one on a clear day and the other on 
a smoky day. 
We have received from the Cambridge University 
Press a copy of the second edition of .Dr. G. S. 
Graham-Smith’s ‘‘ Flies in Relation to Disease : Non- 
Bloodsucking Flies,’ the first edition of which work 
was reviewed in Nature of December 11, 1913. In 
the work as first issued an attempt was made to 
collect, tabulate, and examine critically the various 
facts and hypotheses relating to the life-histories, 
habits, and disease-carrying potentialities of non- 
blood-sucking flies, which had been published up to 
92.338; VOL. 93 | 
NATURE 
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the’ end of 1912. In the present edition the worl 
published during 1913 is dealt with in the same 
manner, and in addition an account of some recent 
unpublished observations made by the author has 
been added. The volume is published at 12s. 6d. 
net. 
OUR ASTRONOMICAL COLUMN. 
THe PerRsEID METEORIC SHOWER.—The weather has 
been very favourable for tracing the progress of this 
shower. On August to there were not many meteors, 
though a few tine ones appeared. On August 11 
there was a great increase in numbers, but the moon 
rose soon after g p.m. At Bristol Mr. Denning esti- 
mated that the total number of meteors visible to one 
observer between 9 p.m. and 3 a.m. on the following 
day must have been about 150. On. August 12 the 
rate of meteoric apparitions had declined and the num- 
ber visible in the same time was estimated at IIo, 
but there were many detached clouds over the sky. 
On August 13 there were clouds at Bristol and few 
meteors were seen, but the Perseid shower had 
evidently decreased in a marked degree since the 
previous night. On the whole the display may be 
regarded as having exhibited moderate numbers with 
a large proportion of brilliant meteors. The radiant 
point showed the usual displacement to the eastward 
as observed on successive nights. 
On August 16 meteors were abundant, and there 
were two active showers, one of late Perseids from 
56°+59° and another of Lyrids from 279°+45°. 
The observations generally have been ample this 
year, according to reports from many stations. Mrs. 
Fiammetta Wilson, at Bexley Heath, recorded the 
paths of no fewer than 152 meteors on the four nights 
from August 10-13. Two magnificent fireballs were 
seen by her and by Miss Grace Cook at Stowmarket 
on August 14, viz., a Perseid at 9.34 and a slow 
meteor three or four times as bright as Venus 
directed from a radiant in the southern sky at 9.50. 
The latter was also recorded by the Rev. Ivo Gregg at 
Walthamstow, and the following deductions have been 
made regarding this and a few other brilliant meteors 
of the recent display :— 
Height Height p,,, Velocity pogiant 
Date G.M.T. Mag. at first at end per sec. 
Diep eres m. m. m. m. ‘ < 
Aug. II II 25 >I 72 48 38 38 47+ 61 
12) 70.22) ‘Sirius 78 45 59 45 48+ 58 
SE ONsoane Paw 80", 54 948) 40'' 45-657 
i 1Ouj2h 8 > Te 382 53 31 80 2804+44 
Py: II 10 I 64 49 28 14 320-4 
147g 0834 Qe BG G4 Old. GI aaa 
14 QUSO Om G7 44 31 16 296+10 
The great velocity of the Lyrid of August 12, 10 525, 
is remarkably in contrast with the rate of motion of 
the last two meteors in the table. 
THE SPECTRUM OF Comer 1914b (ZLATINSKy).—Dr. 
Slipher publishes in the Lowell Observatory Bulletin, 
No. 63, a description with wave-lengths of the spec-. 
trum of Zlatinsky’s comet. Three spectrograms of 
this comet were secured at Flagstaff on the evenings 
of May 25, 26, and 27, using a one-prism_spectro- 
graph employed in nebular work attached to the 24-in. 
refractor. Vanadium and iron were used as com- 
parison spectra, and it was possible to expose for 
about one and one-third hours. The wave-lengths 
were reduced independently from the three negatives, 
and all three reductions are printed in tabular form 
in the paper. In order to differentiate between the 
spectrum of the head and nucleus of the comet a long 
