Kirk wood.] ^40 [May 2, 



A luminous cloud of smoke or vapor remained visible several minutes 

 after the explosion. No sound was noticed.* 



Remarks. 



As already stated, no meteorites are known to have fallen from any 

 of the fireballs in the preceding list ; although in more than one case the 

 disappearance was followed by loud detonations, and the explosion of the 

 meteor of February 3 took place near the zenith of the principal point of 

 observation. It is also remarkable that the only two whose velocities 

 could be approximately determined were almost certainly moving in hy- 

 perbolic orbits. This last mentioned fact is in harmony with the theory of 

 Professor Von Neissl, who regards aerolitic and denotating meteors as a 

 distinct class of cosmical bodies, differing both from comets and periodic 

 star showers in the original velocities with which they enter the sphere of 

 the Sun's attraction.! But not only have certain comets moved in hyper- 

 bolas but the computed velocities of at least a few bolides have undoubtedly 

 indicated elliptic motion. This theory therefore can hardly be accepted 

 without further confirmation. 



Are meteoroids moving in hyporbolas to be regarded in general as fragments 

 of disintegrated comets? — The discovery that the meteors of November 14, 

 November 27, April 20, and August 10, are intimately connected with comets 

 moving in the same orbits, has suggested that all shooting stars and mete- 

 oric fire-balls may have been produced by the gradual dissolution of comets 

 or cometary clusters. It must be remembered, however, that the comets 

 connected with these meteor streams are all periodic, and that the disper- 

 sion of their matter is due to an indefinite number of returns to perihelion. 

 In cases of non-periodicity complete dissolution, as the result of a single 

 perihelion passage, would be extremely improbable. We conclude there- 

 fore, that the meteor of December 30, 1878, and others with hyperbolic 

 orbits are not cometary fragments dissevered by solar influence. 



That some fireballs explode noiselessly, while others, apparently no larger, 

 produce loud detonations, is a remarkable fact not hitherto explained. The 

 fact also that explosions very often occur without being followed by the 

 fall of aerolites seems no less mysterious. Professor Newton has sug- 

 gested that aerolites are probably furnished only by such meteors as pene- 

 trate the atmosphere with relatively slow motions ; those moving with 

 great velocities being burnt up or dissipated before reaching the earth's 

 surface. Much, however, must evidently depend on the size and constitu- 

 tion of the meteoroids. Small meteors (shooting stars) are entireby consumed 

 in the atmosphere. The composition and structure of meteoric stones are 

 very widely various. "While some are extreme^ hard, others are of such 

 a nature as to be easily reducible to powder. It is not impossible that when 

 some of the latter class explode in the atmosphere they may be completely 

 pulverized, so that, reaching the earth in minute particles, they are never 



* Letter from Prof. D. E. Hunter. 



t See the Report on Luminous Meteors by a Committee of the Brit. Assoc, for 

 the Ail v. of Sri. for 1877. 



