SCIENTIFIC SUMMAEY. 
103 
of this ingenious theory. It is founded on the principle, however, that 
meteors fall without preference from aU directions ; hut from Mr. Greg’s 
observations it would appear that there are ephemeral swarms of meteors 
which proceed from a common source. Mr. Herschel has calculated the 
relative number of meteors which should faU at any particular latitude, and 
finds that his theory agrees very exactly with observation. It is to be 
noticed, that not only ordinary shooting-stars but also fire-balls and aerolites 
and star-showers are more abundant in autumn than in spring, Mr. Greg, 
finding that the proportion of the first six months of the year to the last 
half being as 739 to 1,059. M. Quetelet finds that star-showers occur at the 
same periods in the proportion of 28 to 72. 
Mu Herculis. — In 1856, Mr. Alvan Clark discovered the small star south 
preceding Mu HercuHs to be a close double star, the distance being about 
two seconds. Mr. Dawes now finds that since that period it has changed in 
position, the variation amounting to eighteen degrees. As Struve ascertained, 
many years since, that 'Mu Herculis and the small star formed a binary sys- 
tem, it follows that it is now a triple system similar to that of Mu Bootis. 
Mr. Dawes remarks, that as the small star of Mu Herculis was observed by 
Struve so late as 1851 without its duplicity having been noticed, it would 
appear that the distance must have been considerably less at that time, 
although no variation has been noticed since 1857. 
Bright Band smn on Moon’s Border. — The cause of this phenomenon, 
which has been noticed in the photographs of solar eclipses, has been examined 
by the Astronomer Koyal. He finds that when first looked at, it is seen 
rather conspicuously ; when most distant from the eye, it appeared broadest ; 
when brought suddenly nedr, it seemed to vanish, but, on looking carefully, 
it was found to exist, but much narrower than before. A piece of the thin 
black photographic paper was then cemented on the bright portion, but the 
same phenomenon was visible ; from which Professor Airy thinks that it is 
an optical illusion, or nervous irritation of the retina, produced by the view 
of the conterminous black-and-white portions of the photograph. 
Solar Eclipses. — Mr. Williams gives an interesting catalogue of solar 
eclipses, of which he finds accounts in the Chinese historical records. The 
present list extends from b.c. 481 to the Christian era. Although observa- 
tions of comets are numerous, no lunar eclipses are mentioned. 
New Telescope. — Dr. Steinheil has constructed a refracting telescope, of 4j 
inches aperture, and only 40 inches of focal length, of which Mr. De la Eue 
reports most favourably. He is now engaged upon one of 6 inches aperture, 
and the extraordinarily small focal length of 30 inches. 
Double Stars. — Mr. Dawes publishes a list of fifteen very close double stars 
detected by him accidentally within the last twenty years. 
AGKICULTUKE. 
Advantages of Artificial Manures. — The comparative merits of the arti- 
ficial and natural manures have been demonstrated to French agriculturists by 
M. G. Villes, the superintendent of the Government experimental farm of 
Belle Eau. This gentleman gave the local farmers a series of lectures and 
demonstrations on the subject of manures. He showed them several fields of 
