294 METEORS AND AEEOLITES. 



form is always circular. The amount of their illumination is 

 much less than that of the moon. Their height is various, 

 but often far beyond the limits of our atmosphere. They 

 appear and disappear suddenly, without sensible change of 

 diameter ; sometimes bursting, but without noise ; and often 

 leaving a train of light behind. Their duration seldom ex- 

 ceeds a few seconds. Their velocity approximates to that of 

 the earth, or other planets. 



One curious fact relating to these meteors, and still more 

 to shooting-stars, is, that they appear now and then to ascend ; 

 or to alternate in ascent or descent, as if new and opposite 

 forces were suddenly brought into action. Chladni and 

 others have sought explanation of this, either in resistance 

 of the air compressed by rapid descent, or in the effects of 

 explosion or ignition in the masses themselves. More re- 

 cently, however, doubts have been suggested by Bessel an 

 authority entitled to much weight on this subject as to the 

 reality of these appearances. It is a point open to future 

 observation and enquiry. 



As is the case in every other part of science, the record of 

 facts regarding these igneous meteors has become of late 

 years infinitely more copious and exact. We have already 

 noticed the extraordinary Chinese register, brought down 

 from a very remote date. No other country, nor any age 

 before the present, furnishes a like document. The first 

 formal catalogue of remarkable meteors, of all classes, is that 

 of a very eminent observer, M. Quetelet, published in 1837 ; 

 and again with large additions in 1841. There soon fol- 

 lowed the catalogue of Mr. Herrick in America, and that of 

 M. Chasles, presented to the Academic des Sciences in 1841, 

 containing much curious retrospective information, and 

 particularly as to the recorded falls of shooting-stars. The 

 latest catalogue is that by Professor Baden Powell ; pre- 

 sented in series at the last five meetings of the British 



