l REPORT—1857. 
have attracted fresh interest to the study of the solar surface; and, upon the 
suggestion of Sir John Herschel, a photo-heliographic apparatus has lately 
been established at Kew, for the purpose of depicting the actual macular 
state of the Sun’s surface from time to time. 
It is well known that Sir William Herschel accounted for the solar spots 
by currents of an elastic fluid, ascending from the body of the Sun, and pene- 
trating the exterior luminous envelope. A somewhat different speculation 
of the same kind has been recently advanced by Mosotti, who has endea- 
voured to connect the phenomena of the solar spots with those of the red 
protuberances, which appear to issue from the body of the Sun in a total 
eclipse, and which so much interested astronomers in the remarkable eclipse 
of 1842. 
Next to the Sun, our own satellite has always claimed the attention of 
astronomers, while the comparative smallness of its distance inspired the hope 
that some knowledge of its physical structure could be attained with the 
large instrumental means now available. Accordingly, at the Meeting of 
the Association held at Belfast in 1852, it was proposed that the Earl of 
Rosse, Dr. Robinson, and Professor Phillips be requested to draw up a Re- 
port on the physical character of the Moon’s surface, as compared with that 
of the Earth. That the attention of these eminent observers has been 
directed to the subject, may be inferred from the communication since made 
by Professor Phillips to the Royal Society on the lunar mountain, Gassendi, 
and the surrounding region; but I am not aware that the subject is yet ripe 
for a Report. 
I need not remind you, that the Moon possesses neither sea nor atmo- 
sphere of appreciable extent. Still, as a negative, in such case, is relative 
only to the capabilities of the instruments employed, the search for the indi- 
cations of a lunar atmosphere has been renewed with every fresh augmen- 
tation of telescopic power. Of such indications the most delicate, perhaps, 
are those afforded by the occultation of a planet by the Moon. The occul- 
tation of Jupiter, which took place on the 2nd of January last, was observed 
with this reference, and is said to have exhibited no hesitation, or change of 
form or brightness, such as would be produced by the refraction or absorp- 
tion of an atmosphere. As respects the sea, the mode of examination long 
since suggested by Sir David Brewster is probably the most effective. If 
water existed on the Moon’s surface, the Sun’s light reflected from it should 
be completely polarized at a certain elongation of the Moon from the Sun. 
No traces of such light have been observed; but I am not aware that the 
. observations have been repeated recently with any of the larger telescopes. 
It is now well understood that the path of astronumical discovery is ob- 
structed much more by the Earth’s atmosphere, than by the limitation of 
telescopic powers. Impressed with this conviction, the Association has, for 
some time past, urged upon Her Majesty’s Government the scientific import- 
