aes 
Marcu 11, 1897] 
INWATURKE 
447 
OUR ASTRONOMICAL COLUMN. 
DRAWINGS OF MercuRY.—Mr. Percival Lowell, writing 
(Astr. Nach., No. 3407) of the planet Mercury, says that the 
markings of the planet are distinct and dark. They are 
generally of the nature of lines. Both poles, he says, are 
shaded, and there is a conspicuous dark band cutting off the 
southern one from the rest of the planet. This band is stated 
to be continuous for several degrees of longitude, and may 
possibly girdle the zone completely. The period of rotation of 
the planet was found to be synchronous with the orbital revo- 
lution, thus endorsing Schiaparelli’s previously determined period 
of eighty-eight days. Even from the drawings, several of 
which are reproduced, a slow period of rotation seems the more 
probable, while observations made since they were completed 
confirm this still more. 
PROMINENCE PHOTOGRAPHY.—During the last twelve 
months many attempts have been made to obtain impressions on 
a photographic plate, showing various solar phenomena, and all of 
them have had for their basis the well-known action of electrical 
radiation ona sensitive film. -The method consists in wrapping 
a plate in some opaque material, velvet, tinfoil, paper, &c.. and 
then exposing it to the sun, using either the general diffused 
light, or the image formed by an object-glass or in a pin-hole 
camera. In several cases results have been obtained more or 
less consistent, but in general the impressions have been dis- 
similar at each trial, thus suggesting accidental causes for the 
effect. In the Photogram for July 1896, Mr. D. Packer gave 
several photographs of impressions he had obtained on plates 
exposed in this way, which were supposed to show the details 
of the solar corona. Results exactly similar to those given have 
been obtained by the writer, but in every case the effect could be 
traced to imperfections in the wrapping of the plat., and the 
consequent spreading of the light thus admitted direct to the film. 
Now in the current Comptes rendus (p. 459), M. P. de Heen 
describes the appearance he gets on exposing a covered plate at 
the focus of a small object-glass. He finds that a ring is pro- 
duced on the plate, corresponding to the solar atmosphere in 
size, and thinks that the chromosphere is the seat of electric 
radiations, while the photosphere is simply the source of 
luminous radiation, thus suggesting that, if true, this may 
furnish a method of examining the spots and prominences. 
OXYGEN IN THE SuN.—Some time ago (NATURE, vol. lv. 
p. 303) we pointed out in this column that Herren Runge and 
Paschen had reason to believe that the three lines of oxygen— 
7772°26, 7774°30, and 7775°97—1in the solar spectrum were 
probably not atmospheric, and we further mentioned that a 
crucial test could be made by examining the solar spectrum for 
motion in the line of sight. Mr. Lewis Jewell has taken up 
this problem, and contributes the result of his inquiry to the 
Astrophysical Fournal (February 1897, p. 99). He found that 
using a grating, 15,000 lines to the inch, the spectrum was so 
"exceedingly weak to the eye when the slit of the spectroscope 
was placed near the edge of the sun’s disc, that no satisfactory 
observations of the three lines mentioned above could be 
made. 
Mr. Jewell then turned his attention to investigating whether 
a high or low sun caused any appreciable difference in intensity 
of these lines. In this he was more fortunate, and is now able 
to state that his observations ‘‘ prove conclusively that the three 
lines supposed to be due to oxygen in the sun are produced by 
water vapour in the earth’s atmosphere.” 
THE ToraL SoLar Ec.iiresE or Aucust 8, 1896.—In the 
January number of the Bud/e¢in of the St. Petersburg Imperial 
Academy of Sciences (5th series, vol. vi. No. 1) appear three 
accounts of the observations made at Novaya Zemlya. The 
first is the report of Prof. O. Backlund, whose station was 
situated at Malya Karmakouly, and whose programme con- 
sisted in observing the contacts and sketching the corona. The 
weather seemed to have been all that could be desired, and all four 
contacts were obtained. The second report ismade by M S. 
Kostinsky and A. Hansky, who observed from the same station. 
This is accompanied by some excellent reproductions taken 
direct from the enlarged negatives, showing an amount of 
detail in the streamers that is seldom obtained. One photo- 
graph was taken about third contact, and shows that interesting 
phenomenon known as ‘‘ Baily’s beads,” which interferes so 
much with the estimation of the exact observed time of contact. 
There is also a plate showing the corona and a large region of 
NO. 1428, VOL. 55] 
the sky around it : conspicuous on this are Jupiter and several 
stars. An excellent drawing of the details, as gathered from 
a minute examination of all the photographs taken, is further 
added. Lieut. Bouchteeff, who was carrying on some hydro- 
graphic operations at Novaya Zemlya, observed the eclipse 
from the Bay of Belougia Gouba. He: noted the times of all 
four contacts, and made a rough sketch of the corona, which 
are all given in his report published in this Bzd/etzn. 
THE CHEMISTRY OF THE STars.—The rapid strides that 
have been made in the development of spectrum analysis since 
the time of Wollaston, and the important step taken by Prof. 
Pickering in the adoption of the prismatic-camera form of in- 
strument, have led many to investigate the spectra of the stars 
in our universe. Such a survey, although slow to accom- 
plish, is of great importance, since we are able to pass at a 
bound from terrestrial temperatures, and observe the behaviour 
of our elements at temperatures far beyond our ken. The 
chemist is thus left far behind. and is restricted to a very limited 
range of temperature, while the astronomer has at his disposal 
temperatures the magnitude of which cannot be even conceived. 
That the celestial bodies about us vary enormously in their 
degrees of temperature is now admitted by every one, and some 
idea of the different kinds of spectra emitted by these bodies 
may be gathered from Mr. Fowler’s interesting article in 
Knowledge (March), which deals in the main with the im- 
portant work that is being carried on at Kensington under the 
direction of Mr. Norman Lockyer. That the stars are now 
being successfully classified in a closed curve—?z.e. some are 
increasing and some decreasing their temperatures—is only one 
of many important advances of the last few years. The recent 
discovery of the new form of hydrogen, by Prof. Pickering, is 
another rundle in the ladder of temperature, which seems to 
indicate that even in those stars within our sphere of the 
cosmos we may not have examples of the Azghest attainable 
temperature, 
ON ELECTRIC EQUILIBRIUM BETWEEN 
URANIUM AND AN INSULATED METAL 
IN ITS NEIGHBOURHOOD. 
THE wonderful fact that uranium held in the neighbourhood 
of an electrified body diselectrifies it, was first discovered 
by H. Becquerel. Through the kindness of M. Moissan we 
have had a disc of this metal, about five centimetres in diameter 
and a half-centimetre in thickness, placed at our disposal. 
We made a few preliminary observations on its diselectrifying 
property. We observed first the rate of discharge when a body 
was charged to different potentials. We found that the quantity 
lost per half-minute was very far from increasing in simple pro- 
portion to the voltage, from 5 volts up to 2100 volts; the 
electrified body being at a distance of about 2 cms. from the 
uranium discs. [Added March 9.—We have to-day seen Prof. 
Becquerel’s paper in Comptes rendus for March 1. It gives us 
great pleasure to find that the results we have obtained on dis- 
charge by uranium at different voltages have been obtained in 
another way by the discoverer of the effect. A very interesting 
account will be found in the paper above cited, which was read to 
the French Academy of Sciences on the same evening, curiously 
enough, as ours was read before the Royal Society of Edinburgh. | 
These first experiments were made with no screen placed 
between the uranium and the charged body. We afterwards 
found that there was also a discharging effect, though much 
slower, when the uranium was wrapped in tinfoil. The effect 
was still observable when an aluminium screen was placed 
between the uranium, wrapped in tinfoil, and the charged body. 
To make experiments on the electric equilibrium between 
uranium and a metal in its neighbourhood, we connected an 
insulated horizontal metal dise to the insulated pair of quad- 
rants of an electrometer. We placed the uranium opposite this 
disc, and connected it and the other pair of quadrants of the 
electrometer to sheaths. The surface of the uranium was 
parallel to that of the insulated metal disc, and at a distance of 
about 1 cm, from it. It was so arranged as to allow of its easy 
removal. ; 
With a polished aluminium disc as the insulated metal, and 
with a similar piece of aluminium placed opposite it, in place of 
the uranium, no deviation from the metallic zero was found when 
the pairs of quadrants were insulated from one another. With 
1 By Lord Kelvin, Dr. J. Carruthers Beattie, Dr. M. Smoluchowski de 
Smolan. Read before the Royal Society of Edinburgh, March x. 
