442 
POPULAR SCIENCE REVIEW. 
gave the result of tlieir observations on the sliooting-stars during the nights 
of the 9th, 10th, and 11th of August of this year. They showed, by a 
tabular statement, that from the 5th of August, the mean hourly number 
at midnight in a clear sky — that is to say, corrected for the lunar light and 
the presence of clouds — was 16'2 stars; this became 33-7 on the 9th, 49-9 
on the 10th, and 28’7 on the 11th, giving an average of 374. Comparing 
this with the year 1848, which had given, for the mean hourly number, 
110 meteors, it seems that the quantity diminishes very sensibly. 
Behaviour of the Aneroid Barometer. — On this subject a very valuable 
paper was read by Dr. Balfour Stewart at the recent meeting of the British 
Association in Dundee. Experiments had lately been made with the view 
of ascertaining to what extent an aneroid may be considered a reliable in- 
strument when exposed to considerable changes of pressure, such as occur 
in mountain districts. By means of an air-pump, the aneroids, when 
placed in a receiver, may be subjected to any pressure. A method of tap- 
ping the aneroids had also been devised, and by this means the experiments 
as to the deviation of the results given by these instruments were conducted 
with comparative ease, and with the greatest accuracy. The experiments 
are still going on. Sir William Thomson, in commenting on Dr. Ste- 
wart’s communication, said the aneroid had become so popular an instru- 
ment, that many had satisfaction in learning that it was capable of giving 
results with scientific precision. Dr. Stewart had shown that in taking a 
barometer up a mountain of 12,000 feet, the error would only be about 
300 feet, and had also shown how to correct this error. By carefully using 
these instruments, therefore, they had a probability of determining, with 
much less probability of error, the height of a mountain of 12,000 feet. 
Lunar Maps . — Mr. Birt recently issued two lunar maps, in red outline, 
with all the present known objects marked, in order that those who 
find any variation in the objects may mark them in black. These maps, 
which contain 203 objects, are on a scale of 200 inches to the Moon’s 
diameter, and comprise the space included between 0° and 6° West longi- 
tude, and 0° and 10° South latitude. 
The Memoirs of the Astronomical Society. — It is stated that the Council 
of the Boyal Astronomical Society have resolved that in future the Memoirs 
of the Society shall be given to all Fellows applying for them, and that 
this regulation will commence with the volume preparing for the current 
year. The subject has occupied the attention of the Council on several 
occasions before, but the expense was considered too great. 
The Dusky-ring of Saturn. — Mr. G. E. Chambers, having made a mis- 
statement in regard to the history of the discovery of the u dusky-ring,” 
writes to the editor of the Astronomical Register to correct his mistake. 
The erroneous paragraph appears on page 129 of Mr. Chambers’s Descriptive 
Astronomy, and is as follows : — u On December 3, Lassell, while on a visit 
to Dawes, saw 1 something like a crape veil covering a part of the sky 
within the inner ring.’ This observation, it would stem, was not made in 
consequence of any hint given by Dawes as to what he himself had seen, so 
Lassell must be regarded as a third or (reckoning Galle) a fourth inde- 
pendent discoverer.” Mr. Chambers makes the following explanation : — “I 
have satisfied myself that the passage italicised is entirely the reverse of 
