528. FIFTH HYPOTHESIS. The last hypothesis is that of Chaldni, and is explained in Art. 555. In this the ignition and explosion of the meteorite are attributed to precisely the same causes as those assigned in the

fourth hypothesis. 66

CHAPTER II.

OF SHOOTING-STARS AND METEORIC SHOWERS.

529. Shooting-stars or meteors differ from meteorites in several particulars. They commonly possess a superior velocity, and their altitude is generally greater: bursting from the clear sky, they dart along the heaven like a rocket, consuming themselves in their course, and leaving behind a luminous train, which gradually vanishes in a short time. Unlike the meteorite they usually pass away without any explosion, and no portion of the body ever reaches the earth. Besides, they are far more numerous and frequent; appearing almost every night, and at times descending in such multitudes that the heavens are illumined for hours with their glowing trains.

530. ALTITUDE. In order to investigate the phenomena of shooting-stars, Brandes and Benzenberg, two German philosophers, made a series of simultaneous observations in the fall of the year 1798. On six evenings, between September and November, 402 shootingstars were beheld, and of these twenty-two were SO identified, that their altitudes, at the moment of their extinction, could be readily computed. They were found to be as follows:

7 disappeared at altitudes under 45 miles.

In what particulars do shooting-stars and meteors differ from meteorites ? Relate the account of the observations of Brandes and Benzenberg, for determining the altitudes of shooting-stars?

Give their results.

The least and greatest elevations were six miles and one hundred and forty.

531. In 1823, the investigation was renewed by Brandes, at Breslau and the neighboring towns, on a more extended scale. Between April and October, 1800 shooting-stars were seen at the different stations. Out of this number, 98 were observed simultaneously at more than one station, and afforded the means of estimating their respective altitudes. The results were as follows:

4 disappeared at altitudes under 15 miles.

15

66

between 15 and 30 miles.

Out of the last eleven, two vanished at an elevation of 140 miles, a third at 220 miles, a fourth at 280 miles, and a fifth at 460 miles.

The height of four shooting-stars noticed by Professors Loomis and Twining, in December, 1834, varied from 54 miles to 94.

532. Similar observations were made in Switzerland, on the 10th of August, 1838, by Wartman and others. A part of the observers stationed themselves at Geneva, and the rest at Planchettes, a village about sixty miles to the north-east of that city. In the space of seven hours and a half, 381 shooting-stars were seen at Geneva, and in five hours and a half 104 at Planchettes. All the circumstances attending their appearance were carefully noted, and their average height was computed at five hundred and fifty miles.

533. VELOCITY. In the first series of observations made by Brandes and Benzenberg, only two shootingstars afforded the means of determining their speed; one possessed a velocity of 1500 miles per minute, and

Give those of Loomis and Twining.

Give those of Wartman, at Geneva.

What is their velocity according to the observations of Brandes and Benzenberg, and Quetelet?

that of the other was between 1020 and 1260 miles per minute.

In the second series, undertaken in 1823, the estimated rate of motion varied between 1080 and 2160 miles per minute. At Belgium, in 1824, M. Quetelet obtained observations upon six of these singular bodies, from which he was enabled to deduce their respective velocities, which were found to range from 600 to 1500 miles per minute.

534. COURSE. Of thirty-six stars, whose paths were ascertained by Brandes, the motion in twenty-six cases was downward, in one horizontal, and in the remaining nine, more or less upward; nor did they always move in straight lines; for the paths of some were curved, either upwards or sideways; while others proceeded in a serpentine course. Their general direction was from north-east to south-west. Several examples have been given by Chaldni, where the luminous body described a semicircle, first rising and then falling.

535. MAGNITUDE. The size of shooting-stars is variable. Fire-balls, which are regarded as nothing more than large meteors, have sometimes appeared of a magnitude almost incredible. During the remarkable shower of meteors, on the 12th and 13th of November, 1833, luminous globes, apparently as large as Jupiter and Venus, were seen darting through the air in all directions. About three o'clock on the morning of the 13th, a splendid body which appeared equal in size to the full moon, swept across the heaven from east to west. If the distance of this meteor was only eleven miles, its diameter must have been 528 feet, or one tenth of a mile. Amid the shower of stars that occurred in 1799, meteors were observed by Humboldt, apparently twice the size of the moon.

536. On the evening of the 18th of May, 1839, a meteor of extraordinary magnitude passed over the

What is said respecting the course of shooting-stars?

What of their magnitude?

Relate the account of the meteor of the 18th of May.

Northern States and a part of Canada. From the facts which he collected, Prof. Loomis estimated its diameter at 1320 yards, or three quarters of a mile. Its velocity was computed by this gentleman to be nearly 2100 miles a minute, its height to be 30 miles, and the length of its path 200 miles. The meteor was followed by a train of inconsiderable extent, probably formed of the detached portions of the body which fell behind.

537. SPLENDOR. At times these luminous bodies present a spectacle of surpassing beauty, from their brilliant coruscations, extended truins, and rich diversity of colors. During the month of April, 1832, a globular ball of fire, apparently a foot in diameter, passed over Torhut, in India, early in the morning. Behind it streamed a train of dazzling light, which appeared to be several yards in length. The meteor illumined the surrounding country to a great distance, and after remaining visible for the space of five seconds, exploded without noise, like a rocket, throwing out numerous coruscations of intense splendor.

In May of the same year, and at the same place, a similar body was seen moving rapidly through the air, from north to south. It glowed with a brilliant mixture of green and blue light, and vanished in about three seconds, leaving a luminous train of great length.

538. During the nights of the 9th and 10th of August, 1839, many shooting-stars of singular beauty were seen by Mr. E. C. Herrick, of New Haven. One flashed with a golden green light, and another sparkled with green and blue. Meteors entirely green have at times been noticed. A meteor which swept over Kensington, near London, in 1839, as brilliant as Jupiter and apparently of greater size, presented the rare combination of white light in the mass, with one edge red and the opposite of a deep blue or purple.

On the morning of the 13th of November, 1833, a most brilliant meteor was seen by Prof. Twining, de

What is said of their splendor?

scending towards the earth with majestic rapidity. Its apparent size was one-fifth that of the moon, and its color a deep red. It vanished when near the ground, leaving behind a fiery train of the same hue, excepting that it displayed the prismatic tints, especially at the point where the meteor expired.

539. The usual color of meteors is that of a phosphoric white tinged with red. The trains generally vanish in a few seconds, but they have been known to last for the space of seven minutes, and even fifteen. Their light (as we have just seen) is not invariably of one hue, for at times it presents to the eye all the rich tints of the rainbow.

METEORIC SHOWERS.

540. The wondrous display of meteors in 1833, drew the attention of philosophers to the subject of shooting stars, and, from the results of subsequent researches and observations, there is now reason to believe, that certain epochs exist when these luminous bodies appear in greater numbers than usual, and that sometimes at the return of these periods they literally descend to the earth in showers. The best ascertained periods are those of the 12th and 13th of November, and the 9th and 10th of August.

541. NOVEMBER EPOCH. On the morning of the 12th of November, 1799, an extraordinary display of this nature was seen by Humboldt and Bonpland, at Cumana, in South America. During the space of four hours the sky was illumined with thousands of shooting-stars, mingled with meteors of vast magnitude. This phenomenon was not confined to Cumana, but extended from Brazil to Greenland, and as far east as Weimar, in Germany.

On the 13th of the same month, in 1831, a meteoric shower occurred at Ohio, and also near Carthagena, off the coast of Spain. At the latter place, luminous meteors of large size were beheld, one of which left behind it an

Are meteors at all times equally abundant?

What two great epochs exist?