420 
POPULAR SCIENCE REYIEW. 
of the Astronomer Royal in 1868. But whose fault is that ? Must science 
he allowed to sutFer merely that a result personally unpleasant to the 
Astronomer Royal may he avoided ? 
Dr. Oudemans' Photographs of the Solar Eclipse of December 11-12, 
1871. — Lieut-Col. Tennant makes the following remarks on two photo- 
gi’aphs of the corona taken for Dr. Oudemans hy Mr. Dietrichs, at Buiten- 
zorg, in Java: — “ These consist of two paper proofs from the original nega- 
tives and two transparent enlargements on glass. In the negatives the 
diameter of the lunar disk is about 3 m.m., so that the equivalent focus of 
the lens must have been about 41 c.m., or 16 inches. Dr. Oudemans 
describes it as No. 10 C. by Liesegang, of Elberfeld. The exposure in each 
case was half a second, and the glass enlargements show that the amount of 
corona depicted was not very materially less than in the photographs at 
Dodabetta and Bekul. The Moon’s limb is, however, very sharp, and the 
small negative has borne enlargement to a lunar diameter of 2 c.m., with 
singularly little loss of definition of the dark edge ; which, too, is very free 
from halation or encroachment from the prominences. In the transparencies 
sent me, however, there is very much less detail in the corona than in the 
Indian photographs. The principal thing to be noted is the very complete 
resemblance of the general form of the corona in the Java photographs and 
in our Indian ones, though there was an hour of diflerence in absolute 
time. I can recognise almost every depression of outline, and the form and 
relative sharpness of the edges of the southern rift, and even of the less 
definite northern one, are very markedly similar. I presume no one now 
believes the corona to be an atmospheric phenomenon ; but these photo- 
graphs show a considerable amount of permanence in its features, and it 
would be very interesting to compare the original negatives, for which pur- 
pose perhaps those of Mr. Dietrichs could be procured.” 
The Radiation of Heat from the Moon. — In his discourse on this subject, 
at the Royal Institution, on May 30 last. Lord Rosse made the-following 
remarks relative to his recent observations for determining the heat radiated 
to us by the Moon : — 
The observations made during the seasons 1868-9 and 1869-70 were 
found to follow pretty well Lambert’s law for the variation of light with 
phase. It was found also that a piece of glass which transmitted 80 per 
cent, of the Sun’s rays suffered only about 10 per cent, of the Moon’s rays to 
pass through \ thus a large amount of absorption before radiation from the 
Moon’s surface was shown to take place. In the earlier experiments no 
attention had been paid to the correction to be applied for absorption of 
heat by the Earth’s atmosphere ; but, as the apparatus was gradually 
improved, it became indispensable to determine the amount of this correc- 
tion before attempting to approach more nearly to the law of variation of 
the Moon’s heat with her phases than had been done in the earlier investi- 
gation. By taking long series of readings for lunar heat through the 
greatest ranges of zenith distance available, a table expressing the law for 
decrease of heat with increase of zenith distance, closely following that 
deduced by Seidel for the corresponding decrease of the light of the stars, 
was obtained. By the employment of this table, the determinations of the 
Moon’s heat at various moments of the lunation were rendered comparable 
and available for laying down a more accurate ‘^phase-curve” than had 
