menon the appearance of a luminous and gigantic dahlia, 
the centre of which was occupied by the black disc of the 
moon, 
The corona did not present any essential differences 
of structure at the point of contact and the opposite point. 
The motion of the moon did not appear to produce any 
change in the structure. These facts completely con- 
vinced me that the corona is a real object, situated beyond 
the moon, the gradual motion of which body reveals its 
various parts. Having finished this investigation, I 
turned my attention to the luminous elements of the 
phenomenon. My view being yet as distinct as ever, I 
commenced by examining the spectrum of the highest 
and least luminous parts of the corona. I placed the 
slit of the spectroscope at a point two-thirds of a radius 
from the moon’s limb (exviron du bord lunaire). The 
spectrum was seen much more vividly than I expected 
at that distance, a result evidently due to the luminous 
powers of the telescope and to the whole of the arrange- 
ments adopted. This spectrum was not continuous. I 
recognised at once the hydrogen lines and the green ray 
(1474).* “ 
This is one point of the highest importance; I 
removed the slit, remaining always in the high regions of 
the corona ; the spectra always presented the same con- 
stitution. 
Starting from one of these positions, I descended little 
by little towards the chromosphere, examining very care- 
fully the changes which might be produced. In propor- 
tion as I approached the moon, the spectra became more 
distinct and appeared richer, but they remained similar 
to the above in general constitution. In the middle 
heights of the corona, from 3’ to 6’ of arc, the dark 
line D was seen, as well as some obscure lines in the 
green; but these are at the limit of visibility. This 
observation proves the presence in the corona of reflected 
solar light, but it is seen that this light is drowned in an 
abundant extraneous (¢¢7angére) luminous emission, 
I then set myself to a very important observation, 
which I expected would give me the spectral relations 
between the corona and the protuberances. The slit was 
adjusted so as to take in a portion of the moon, a 
protuberance, and all the height of the corona, The 
spectrum of the moon was excessively pale ; it appears due 
principally to atmospheric illumination, and gives a 
valuable idea of the feeble part which our atmosphere 
can play in the phenomenon of the corona. 
The protuberance gave a very rich spectrum and one 
of great intensity; I had not time to make a detailed 
examination. The main point here is the establishment 
of the fact of the prolongation of the principal rays of 
the protuberance through all the height of the corona, 
which clearly demonstrates the existence of hydrogen in 
the latter. 
The green line (1474), so vivid in the spectrum of the 
corona, appeared interrupted in the spectrum of the 
protuberance—a very remarkable result. I then gave a 
few moments to establish satisfactorily the exact cor- 
respondence of the lines of the corona with the principal 
lines of hydrogen in the protuberances, 
There remained to me then only a few seconds for 
polariscopic observation.t The corona presented the 
characteristics of radial polarisation, and, it ought to 
be remarked, the maximum of effect is not observed at 
the lunar limb, but at some minutes from the edge. t 
I had scarcely finished this rapid investigation when the 
sun reappeared. JANSSEN 
(To be continued.) 
* My spectroscope was fitted with a very exact scale ; but it will be seen 
how I afterwards made use of the lines of a protuberance as a scale. 
+ Tostudy polarisation, Ihave an excellent lunette excellently constructed 
of biquartz, by M. Prazmowski. This polariscope, placed upon and 
adjusted to the telescope, can be consulted in an instant. 
t M. Prazmowski has noted this fact in his excellent polariscopic obser- 
vations of the eclipse of July 17, 1860. 
129 
NOTES 
THE subject of the Transit of Venus in 1874 was for the 
first time officially brought before the notice of the Board of 
Visitors at the recent Visitation of the Royal Observatory. 
After a careful exposition of the matter by the Astronomer 
Royal, and a consideration thereof by the Visitors, it was pro- 
posed and seconded by the Astronomical Professors of Cambridge 
and Oxford, that the Government be requested to provide the 
means of organising some parties of observers in the Southern 
Ocean, in the hope that they may find some additional localities 
for observing the whole duration of the Transit of Venus. In 
other language, they recommend strongly a sort of roving expe- 
dition. The meteorological and climatic difficulties both North 
and South are extremely great : the practical difficulties in the 
South are very peculiarly so ; in despite of the latter, the Board 
of Visitors were unanimous in their advice to try what best 
can be done in the sub-antarctic regions. The Astro- 
nomer Royal expressed his perfect acquiescence in the 
proposal of the Visitors; the final decision will rest with the 
Admiralty and the Government. In coming to this decision, it 
is proper to add that the Board was in no degree either ine 
fluenced or assisted by certain discussions which have taken 
place upon the subject out of doors ; their decision would have 
been just the same whether these discussions had or had not 
taken place ; and the Board came to their conclusion under a 
full knowledge of the very peculiar climatic and navigational diffi. 
culties which seem to attend on the roving expedition which they 
recommend, It is, in fact, only a realisation of an old proposal 
by the Astronomer Royal himself, which seems to have been set 
aside on account of the many serious practical difficulties attend - 
ing it. The Astronomer Royal also proposed to organise some 
additional stations dependent on Honolulu. 
Messrs. SAMPSON Low AND MARSTON are about to publish 
aivolume on the subject of Arctic Exploration, by Mr. Clements 
Markham, entitled the ‘‘ Threshold of the Unknown Region,” 
It is intended to give a full account of all that is known of the 
line which, at present, separates the known from the unknown ; 
to explain the best route by which the unexplored region may be 
examined ; and to enumerate the important scientific results to 
be derived from Arctic exploration. 
NATURALISTS will be glad to hear that the long-talked-of 
new buildings for the National Museum of Natural History, at 
South Kensington, have been actually commenced, and that the 
contractors, Messrs. Baker, have arranged to complete them 
within three years. 
Mr. F. T. WARNER, of Winchester, who for some time has 
been collecting materials for a Flora of Hampshire, has kindly 
offered the use of his collections and materials to Mr. Frederick 
Townsend with the proposal that he should complete the Flora. 
Mr. Townsend has accepted the offer, and as much work 
remains to be done, he invites the assistance of other botanists 
in furnishing him with lists of plants or in forming these during 
the present season. The value of lists will be greatly increased 
if accompanied by specimens, and in all cases exact localities 
and dates should be given. It is proposed to divide the country 
into river-basin districts. Letters should be addressed to Shed~« 
field Lodge, Fareham, but parcels to Botley Station, London 
and South Western Railway. Mr. Townsend will gladly pay 
postage or carriage of parcels. 
PROFESSOR ROLLESTON, of Oxford, is appointed to deliver 
the Harveian Oration at the Royal College of Physicians on 
June 25, at five o’clock. 
IT is rumoured that Prof. Tyndall is to receive the honorary 
degree of D.C.L. from the University of Oxford during the 
Commemoration, 
