550 Royal Astronomical Society. 



largest are those which have the greatest altitudes, and only the smaller 

 ones appear to come within 20 or even 40 miles of the earth. 



With respect to the casual observations of the phenomena, the ac- 

 counts of which are very numerous, the most interesting conclusion 

 which has been inferred from them is the periodical recurrence of 

 shooting-stars in unusual numbers at certain epochs of the year. Of 

 these epochs, the most remarkable is that of November, on account 

 of the prodigious number of meteors which have been seen in some 

 years at that time. The principal displays were in 1799, 1832, 1833, 

 and 1834. On the 11th of November, 1799, thousands were ob- 

 served within a few hours by Humboldt and Bonpland at Cumana ; 

 and on the same night by different persons over the whole continent 

 of America, from the borders of Brazil to Labrador, and also in 

 Greenland and Germany. On November 12th, 1832, they were 

 seen over the whole of the north of Europe ; and on November 12th, 

 1833, the stupendous exhibition took place in North America which 

 has been so often described. From the accounts of this phenome- 

 non collected by Prof. Olmsted, M. Arago computed that the num- 

 ber of meteors on this night amounted to 240,000. In 1834, a si- 

 milar phenomenon recurred on the night of November 13th, but on 

 this occasion the meteors were of a smaller size. In 1835, 1836, 

 and 1838, shooting- stars were observed on the night of November 

 13th, in different parts of the world; but though diligently looked 

 for on the same night in the last few years, they do not appear to 

 have been more numerous than on other nights about the same 

 season, — a circumstance which has shaken the faith of many in their 

 periodicity. 



The second great meteoric epoch is the 10th of August, first pointed 

 out by M. Quetelet; and although no displays similar to those of 

 the November period have been witnessed on this night, there are 

 more instances of the recurrence of the phenomena. In the last 

 three years shooting-stars have been observed in great numbers, 

 both on the 9th and 10th ; but they appear in general to be unusually 

 abundant during the two first weeks of August. The other periods 

 which have been indicated are the 1 8th of October, the 23rd or 24th 

 of April, the 6th and 7th of December, from the 15 th to the 20th of 

 June, and the 2nd of January ; and it is not improbable that further 

 observations will add to the number. 



The different theories which have been given to explain the origin 

 and phenomena of the shooting- stars are next stated. The following 

 are the principal : — 



1. That the shooting-stars and fire-balls are substances projected 

 from volcanoes in the moon. It is known that a body projected 

 vertically from the moon with a velocity of about 8500 feet in a 

 second would not fall back upon the lunar surface, but would recede 

 from it indefinitely ; and, in order to reach the earth, the projectile 

 would only require, under the most favourable circumstances, to 

 have a velocity of about 8300 feet. Such a velocity, which is only 

 about four or five times greater than that of a cannon-ball, is quite 

 conceivable ; but the extraordinary exhibitions of 1799 and 1833, to 



