Outlines of Meteoric Astronomy. 211 



able fire-balls observed in England in those years. The dis- 

 charge of electricity is, unfortunately for this theory, exceed- 

 ingly diffuse in thin air, while the light of fire-balls is brilliant 

 and intense. The explanation of luminous meteors now 

 generally accepted is that due to Chladni, of Wittemberg, 

 well known for his researches in the theory of sound, and 

 from whom are named the figures formed on glass and other 

 flat surfaces, when strewed with sand, and made to vibrate 

 with a musical note. Chladni visited Grottingen in 1792, 

 where he became acquainted with Lichtenberg's electrical 

 experiments, and was induced to reject the electrical theory of 

 luminous meteors as altogether untenable. The work in which 

 the new views of Ohaldni were made known was published in 

 April, 1794, under the title, " The iron of Pallas and other 

 masses of stone and iron reputed to have fallen from the air." 

 In this work, Chladni supposes that all the accounts hitherto 

 received of the falls of aerolites were founded in reality, 

 and conjectures that the planetary velocity with which these 

 bodies enter the air is sufficient, by compressing the air, to raise 

 them to a heat of vivid ignition. The property of compressed air 

 here assumed can be made evident by an instrument called a 

 fire-syringe, in which air confined by a piston in a tube, and 

 moderately compressed, readily ignites punk, tinder, or amadou. 

 With greater compression a proportionately greater effect might 

 be produced. In this way, not only the fused surfaces of aerolites, 

 but also fire-balls and shooting-stars can be accounted for. It 

 is only necessary to suppose that the latter kinds of meteors 

 are so small as to be consumed before they enter the 

 atmosphere to any depth, and both shooting-stars and fire- 

 balls will be seen to be the same class of bodies as aerolites on 

 a smaller scale. 



(4.) To test this theory, Brandes and Benzenberg, in 1798, 

 undertook to determine the heights and velocities of shooting- 

 stars under the direction of Lichtenberg. The heights were 

 found to be in perfect agreement with Chladni' s supposition. 

 Fire-balls and shooting-stars occur, namely, at a common 

 height of forty to eighty miles above the surface of the earth. 

 Their velocity is somewhat greater than that of the earth in 

 its orbit, and (although they may sometimes appear to do so) 

 they in reality never shoot upwards, but always downwards 

 towards the earth. In this way Chladnr's position was fully 

 confirmed, and more attention came to be paid to the fall of 

 aerolites than they had ever before received. A variety of 

 explanations was at this time hazarded to account for the pre- 

 sence of the flying particles in space. Among these the 

 theory of Toaldo, that meteorites were stones projected by 

 volcanoes from the moon, obtained the most adherents, and 

 VOL. VII. — NO. III. p 



