FEBRUARY 25, 1904] 
Tue Comptes rendus for January 25 contains an account | 
Dewar and 
of the experiments recently made by Profs. : 
radium 
Curie on the gas “‘ occluded or liberated ’’ by 
bromide. Three series of experiments are described. In 
the first series a glass tube containing 0-4 g. of the salt 
was exhausted by means of the mercury pump, and was 
found to liberate gas to the extent of about 1 c.c. per 
month; this gas, examined spectroscopically, gave only the 
hydrogen and mercury spectra. The salt» was then taken 
to the Royal Institution, transferred to a quartz tube, 
nected to the mercury pump, and heated to the melting 
point of the salt; the gas liberated was passed through 
three U-tubes cooled with liquid air to condense the eman- 
ation and the less volatile gases, and collected over mercury. 
The gas, which had a volume of 2-6 c.c. at atmospheric 
pressure, was intensely luminous, and three days’ exposure 
in a quartz spectroscope showed the presence of the three 
chief bands of the nitrogen spectrum. During this time 
the glass tube had become violet in colour, and the yolume 
of the gas had been spontaneously reduced to one-half of its 
original volume. A small sample of the gas was transferred 
to a Geissler tube, and again exhibited the nitrogen bands. 
Finally, the nitrogen in the Geissler tube was frozen out 
by means of liquid hydrogen, when a very high vacuum 
was produced, but the spark spectrum again indicated the 
presence of nitrogen and no other gas. The quartz tube 
containing the fused radium bromide was sealed off whilst 
still vacuous by means of the oxyhydrogen blowpipe 
and taken back to Paris. It was there examined, twenty 
days later, by M. Deslandres, who covered the ends of the 
tube with tinfoil and illuminated the gas by means of a 
Ruhmkorff coil; three hours’ exposure in a quartz spectro- 
scope revealed a complete helium spectrum, but the light 
emitted spontaneously by the tube gave a continuous spec- 
trum free from light or dark bands. 
con- 
Tue additions to the Zoological Society’s Gardens during 
ithe past week include two Ring-necked Pheasants 
(Phasianus torquatus) from China, presented by Mr. 
Eardley Wilmot Holt; an Undulated Grass Parrakeet 
({Melopsittacus undulatus) from Australia, presented by Mrs. 
‘Clement Shorter; a Bullfinch (Pyrrhula europoea), Euro- 
pean, presented by Mr. R. F. Hearnshaw; an Indian 
Python (Python molurus) from India, presented by Mr. 
W. A. Harding; a Citron-crested Cockatoo (Cacatua 
cilrino-cristatay from 
Fox (Canis lagopus) from the Arctic regions, purchased. 
Timor Laut, deposited; an Arctic 
OUR ASTRONOMICAL COLUMN. 
OBSERVED CHANGES ON THE SURFACE OF Mars.—During 
his observations of the Martian surface on April 19, 1903, 
Mr. Lowell, of Flagstaff, was surprised to see that the 
colour of the Mare Erythraum was a decided *‘ chocolate- 
brown,”’ whilst the neighbouring Syrtis was of the normal 
““blue-green.’’ Although the sea was similarly situated 
for observation on March 22, this peculiarity was not seen 
then, therefore the change must have taken place some- 
where between these two dates. 
When this region was again favourably placed for observ- 
ation, viz. on May 26, the Mare Erythrzeum had lost’ the 
brown colour except in the southern regions, and the re- 
maining colour slowly disappeared southwards, until on 
May 29 only a small region near to Hellas was affected, and 
this became normal on May 30. During the next present- 
ation (June 30-July 7) there was no suspicion of any 
chocolate coloration. Taking the time of maximum bright- 
ness of the brown colour as the time of minimum for the 
“* blue-green ’? which it supplants, Mr. Lowell finds that 
this minimum coincides, in point of time, with the minimum 
visibility of the canals, and, further, that the minima also 
coincide in latitude, travelling southwards in each case as 
the number of days since the summer solstice increases. 
NO. 1791, VOL. 69] 
NATURE 
399 
This is plainly shown by the curves and tables in which 
Mr. Lowell displays the results of his observations of the 
respective phenomena. 
From these data he argues that the normal blue-green 
colour is due to vegetation, which, owing to the absence of 
large bodies of water on the planet’s surface, can only 
thrive when fed by the water which fills the canals at the 
melting of the polar snows. He also suggests that the 
brown colour, which accompanied the minimum visibility 
of the canals, is due to the exposure of the bare soil which 
probably covers the beds of such “‘ seas’’ as the Mare 
Erythrasum (Lowell Observatory Bulletin, No. 7). 
THe GrocrapuicaL DistRIBUTION OF METEORITES.—In an 
article contributed to the February number of the Popular 
Science Monthly, Dr. O. C. Farrington, of the Field 
Columbian Museum (U.S.A.), discusses the distribution of 
the meteorites which have been discovered on the earth’s 
surface. He points out that, according to Prof. Berworth, 
of Vienna, about g00 meteorites reach the earth annually, 
but from various causes the number likely to be observed 
is only about 55 per annum, or 5500 per century. As a 
matter of fact, there have only been about 350 recorded falls 
since the fifteenth century, yet there have been 50 well 
authenticated falls in France during the last 100 years. 
Dr. Farrington explains the apparent discrepancy by 
pointing out that on a map of the world, on which he has 
marked the places where meteorites have been found, these 
places are mostly in civilised and thickly populated countries, 
and it may therefore be surmised that the residue are either 
not seen or else not recorded. Another very interesting 
point illustrated by the map is the comparatively large pro- 
portion of meteorites which have fallen in mountainous 
regions (e.g. the Himalayas, the Alps, the Appalachian 
Mountains, &c.), and to explain this Dr. Farrington 
suggests either increased gravitational effects near to these 
mountainous ranges or else the actual mechanical arrest- 
ation of the meteorites by the projecting mountains. 
An analysis of the types of known meteorites discloses 
curious “* grouping ’’; for instance, including both ‘‘ falls ”’ 
and “* finds,’’ it is seen that of the 256 meteorites known in 
the western hemisphere, 182 are “‘ irons ’’ and only 74 are 
““ stones,’’ whilst of the 378 known in the eastern hemi- 
sphere, 299 are “‘ stones’’ and 79 are “‘‘irons.’’ Prof. 
Berworth has suggested that the dry air of the large desert 
areas of the New World has caused the preservation of the 
irens, whilst the moist atmosphere of the Old World has 
caused their disintegration, but Dr. Farrington points out 
that quite a fair proportion of the “‘irons’’ found in 
America have come from the region surrounding the 
Appalachians, where a comparatively moist atmosphere 
obtains. Several other apparent localisations of particular 
types are discussed by Dr. Farrington in his interesting 
article. 
An ATLAS OF SoLaR PHotoGRaPHs.—At the meeting of the 
Paris Académie des Sciences held on February 1, Prof. 
Janssen presented an atlas of photographs of the sun’s disc 
which have been taken regularly at the Meudon Observ- 
atory since 1876. These photographs have been chosen, 
from more than 6000 plates obtained between 1876 and 
1903, in order to show the finest examples of the various 
solar phenomena, and they display a fairly complete history 
of the solar changes during that period. 
The photographs were taken with an especially con- 
structed camera which produces a nearly monochromatic 
image, using the exceedingly actinic light in the violet 
region about HH’. An exposure of 1/3000 of a second was 
generally found sufficient, and therefore the resulting 
pictures show all the finer details of the solar surface beauti- 
fully defined. 
In presenting the atlas Prof. Janssen directed attention 
to the great importance of obtaining such a record at 
several widely separated observatories, because, in the light 
of their inter-relation with meteorological and magnetic 
phenomena, it is obviously desirable to have a complete 
record of the changes which occur on the sun's surface, and 
such a record cannot be secured if only one or two observ- 
atories are taking photographs. Recognising the import- 
ance of this record to meteorologists and physicists, it is 
intended to prepare a large edition of the atlas, on a smaller 
scale, for wide AeA (Comptes rendus, No. 5). 
