Frpruary 18, 1904] 
NATURE 
oLT. 
A RECENT number of the Comptes rendus contains an 
important paper by Prof. Becquerel on the light emitted 
spontaneously by certain salts of uranium. The light 
emitted is out of all proportion to the feeble radio-activity 
of the salts, and is most marked in those salts which 
phosphoresce most brilliantly when exposed to light. In the 
‘case of the double sulphate of uranyl and potassium, it was 
found that whilst different specimens varied in phosphor- 
escent and luminescent power, the light emitted was the 
same, whether the salt had been kept in the dark during 
eight years or had been recently exposed to the light of an 
are or to the radiations of radium salts. It is of interest to 
note that the author is of opinion that the study of uranium 
and thorium would have led, though perhaps somewhat 
slowly, to the recognition of most of the facts which have 
been brought to light by the investigation of radium and 
polonium. 
In the Sitzungsberichte of the Prussian Academy Prof. 
Richarz and Dr. Schenck direct attention to some very 
striking ‘*‘ analogies between radio-activity and the be- 
haviour of ozone.’’ Freshly prepared ozone and ozone that 
has been decomposed by deozonisers have the power of 
causing condensation in a steam jet, and impart con- 
ductivity to the air in a similar manner to those metallic 
salts which emit Becquerel radiation. The photographic 
effect of rddio-active substances has also been observed in 
the case of ozone, and although it does not act upon barium 
platinicyanide or zinc oxide, it causes hexagonal zinc blende 
ito fluoresce brightly, and this is regarded as evidence that 
massive ions are produced comparable with the a rays of 
vadium and the canal rays of the vacuum tube. Platinum 
that has been in contact with ozone exhibits induced radio- 
activity, and it is suggested that the slight conductivity 
normally observed in the atmosphere and certain of the 
effects produced by radio-active bodies may perhaps be due 
to the formation and decomposition of ozone or hydrogen 
peroxide. 
AN ingenious apparatus for measuring the electrical con- 
‘ductivity of aqueous solutions at high temperatures is de- 
scribed by Messrs. Noyes and Coolidge in the Zeitschrift fiir 
phystkalische Chemie. The conditions to be satisfied were 
that the vessel should withstand, without leakage, pressures 
up to the critical pressure of water, that the lining of the | 
vessel should be entirely unacted on by aqueous solutions, 
that the electrodes should be efficiently insulated from the 
walls of the vessel at temperatures exceeding 300° C., and 
that the temperature should be maintained constant within 
o-1° C. The desired result was accomplished by using a 
steel bomb lined with platinum and closed by a washer of 
pure gold wire. The electrodes were of steel covered with 
platinum foil, and were bolted into the top and bottom of 
the bomb, from which they were insulated externally by 
means of mica and internally by means of rings of quartz- 
crystal made tight by gold washers. The whole apparatus 
was heated in a vapour bath, and conductivity measure- 
ments could be made with an accuracy of 0-25 per cent. up 
to 300° C., whilst the fouling of the solutions was in- 
appreciable even at 1/2000 normal. 
Tue additions to the Zoological Society’s Gardens during 
the past week include a Bonnet Monkey (Macacus sinicus) 
from India, presented by Mr. F. Glockler; two Yellow- 
winged Parrakeets (Brotogerys virescens) from Brazil, a 
Senegal Parrot (Poeocephalus senegalus) from West Africa, 
two Golden Eagles (Aquila chrysaétus), European, presented 
by Mr. Charles E. Lister; a Royal Python (Python regius) 
NO. 1790, VOL. 69] 
from West Africa, presented by Mr. Cecil T. Reaney; a 
Simpae Monkey (Semnopithecus melanophus) from Sumatra, 
an Indian Brush-tailed Porcupine (Atherura fasciculata) 
from Siam, a Great-billed Weaver-bird (Ploceus mega- 
rhynchus) from India, deposited. 
OUR ASTRONOMICAL COLUMN. 
EPHEMERIS FOR THE MINOR Pianer (7), Ir1s.—The follow- 
ing is an extract from an ephemeris for the minor planet 
Iris published by Dr. J. Riem in No. 3926 of the Astrono- 
mische Nachrichten. It will be remembered that Prof. 
Wendell recently announced the discovery of a variation in 
the brightness of this planet, having a range of 05 to 1-0 
magnitudes :— 
1904 a. 6 log x log & 
hoviansas: F; h 
Feb. 17’... 6 36126 ... +17 40-5, ....0°332 ... 0°136 
39) 20 pas OO 37M sot beg legs O-334 225.0150 
93. 25) 20. © 38) 30... 07) AIT, .210°330 «5, O 104: 
p35 29 ins OAORIO ..-0-217' 4010) 22 O13 381.27 OF 170 
Mar. 4... 6 42 36... +17 40°4 ... 0°340 ... 0194 
nD .-- © 45 17 .-. +17 39°6... 0°342 ... 0°208 
Magnitude, February 5=7-9, March 8=8:5. 
OxBsERVATIONS OF Mars DURING 1903.—The general 
results of the observations of Mars made by Mr. Denning 
during 1903 are published in No. 3926 of the Astronomische 
Nachrichten. A 10-inch reflector with powers of 252, 312, 
332, 450 and 488 was used, and the power 312 was found 
to be the most effective. 
The streaks, or canals, on the planet’s surface appeared 
to be, without doubt, objective features, but no ‘* doubling ”’ 
was observed. Decided changes were observed to take place 
in the appearance of some of the markings, but Mr. Denning 
attributes these apparent changes to the drifting of vaporous 
condensations over the permanent markings rather than to 
any real modifications of the latter. Many brilliantly 
luminous areas were observed, and although they exhibited 
decided changes, Mr. Denning believes them to be per- 
manent features, and urges that more definite observations 
of their latitudes and longitudes should be made and re- 
corded. A curious feature of these bright markings is that 
they appear brighter when on the edge of the planet’s disc 
than they do at its centre, behaving, in this respect, like 
faculze on the sun’s disc. One rotation period for the planet 
satisfies the observations of all the markings, thus proving 
them to be definite features of the planet’s surface rather 
than drifting vapours such as are seen when observing 
Jupiter and Saturn. 
Comparing the recent results with those obtained in 
February,, 1869, Mr. Denning has determined the rotation 
period of Mars to be 24h. 37m. 227s. As this is the mean 
of 12,136 rotations, it should be a very accurate value. Six 
drawings of the Martian surface, made on different dates 
during 1903, accompany Mr. Denning’s communication. 
A CaTaLoGuE OF 829 SoutH PoLar Stars.—No. 21 of the 
Contributions from the Observatory of Columbia University 
is devoted to a catalogue of 829 stars, all within 2° of the 
South Pole, compiled by Prof. Harold Jacoby, acting 
director of the observatory. 
The star places in the catalogue have been obtained from 
measures of twelve plates taken at the Cape Observatory. 
Four of these plates overlap and cover the region within 1° 
of the pole; the remaining eight contain regions sym- 
metricaliy arranged about the inner four at different hour 
angles, so that they cover the whole region within 2° of 
the pole. In measuring these plates the star places, as 
determined from each plate, were corrected for refraction, 
&c., and then plotted on one large chart, so that the un- 
known stars common to any two or more plates overlapped. 
The effects of errors of observation, and the uncertainty 
due to the possibly different scale-values of each plate, were 
then eliminated, and the whole chart was oriented from the 
known positions of some of the included stars as determined 
by Sir David Gill at the Cape Observatory. The relative 
positions thus determined should be very accurate, and are 
given in the catalogue for the epoch 1895, together with 
