METEORS OF AUGUST AND NOVEMBER. 1^7 



§ VII. — Notice of several Theories of Aerolites and shooting Stars. 



Previous to the researches of Brandes and Benzenberg, the prevailing opi- 

 nion, with some exceptions, was that the shooting stars and fire-balls were of 

 atmospheric or volcanic origin. Halley, whose labours, after Newton, esta- 

 blished the rank of comets as periodical primary bodies of our system, was also 

 of the opinion that the solar system contains myriads of small bodies, moving 

 round the sun in conic sections. Many distinguished astronomers had main- 

 tained the same opinion, and Chladni had entered into an extensive discussion 

 on this subject. He supposed that these isolated bodies pursue their paths in 

 orbits unknown to us, till, by their entrance into the earth's atmosphere, they 

 become luminous by ignition, and either just penetrating the surface of the at- 

 mosphere, leave it to pursue their orbit round the sun, or, entering more deeply, 

 take fire and explode, or fall to the earth in the character of aerolites. 



In 1775 Dr. Olbers,''" in a lecture at the museum of Bremen, suggested the 

 idea of the lunar origin of aerolites, inclining, at the same time, to a belief 

 that they were the product of the earth's volcanoes. The hypothesis of their 

 volcanic origin was thought to receive confirmation from the fall of a shower 

 of aerolites at Sienna, eighteen hours after an eruption of Vesuvius. Mr. 

 Hamilton" had remarked that "stones of the same nature, as far as the eye 

 could judge," had been found on Mount Vesuvius. Dr. Olbers, having com- 

 puted the direction and projectile force required to send these fire-balls from 

 Mount Vesuvius to Sienna in eighteen hours, and having found it not greater 

 than that which is requisite for the up-heaving of mountains, a phenomenon 

 known to have occurred in the historical period, was strongly persuaded of the 

 correctness of the volcanic hypothesis. 



The appearance of Howard's''^ celebrated work on the chemical constituents 

 of these aerolites, in 1802, and of Brandes' and Benzenberg's Researches on 

 the distance, velocity, and orbits of shooting stars, in the same year, threw new 

 light on the subject. The former showed that the chemical constituents of the 



''"Zach's Monatliche Correspondenz, vol. vii., p. 148. 

 ''^ Philosophical Transactions for 1795. 

 "Idem., 1802. 

 VIII. — 2 E 



