162 TENTH ANNUAL REPORT OF 



position of meteorites, they will be seen to liave as strongly marked 

 points of resemblance as minerals coming from the same mountain, 

 I might almost say from the same mine ; and it is not asking much to 

 admit their having a common centre of origin, and that whatever may 

 be the body from which they originate, it must contain no uncom- 

 bined oxygen, and, I might even add, none in the form of water. 



I shall now speak of the origin of meteoric stones. In taking up the 

 theoretical considerations of the subject of the lecture, it is of the ut- 

 most consequence not to consider shooting stars and meteoric stones 

 as all belonging to the same class of bodies — a view entertained by 

 many distinguished observers. It is doubtless less owing to the fact of 

 their having been confounded, that there exists such a difference of 

 opinion as to the origin of these bodies. 



It may be considered a broad assumption that there is not a single 

 evidence of the identity of shooting stars and the meteors which give 

 rise to meteoric stones ; but this conclusion is one arrived at by as 

 full an examination of the subject as I am capable of making.* Some 

 of the prominent reasons for such a conclusion will be mentioned. 



Were shooting stars and meteoric stones the same class of bodies, 

 we might expect that the fall of the latter would be most abundant 

 when the former are most numerous. In other words, the periodic 

 occurrences of shooting stars in August and November, and more par- 

 ticularly the immense meteoric showers that are sometimes seen, 

 ought to be attended with the fall of meteoric stones ; whereas there is 

 not a single occurrence of tliis kind on record. Again : in all in- 

 stances where a meteoric body has been seen to fall, and has been 

 observed even from its very commencement, it has been alone, and not 

 accompanied by other meteors. 



Another objection to the identity of these bodies is the difference in 

 velocity. That of the shooting stars can readily be determined by 

 the simultaneous observations of two observers ; and it has been found 

 that their average rate of motion is about 16| miles a second, while, 

 in order that they should revolve around the earth through the atmo- 

 sphere, their velocity must be less than six miles a second. f Now, we 

 know that the meteors do enter our atmosphere, and probably often 

 pass through it without falling to the eartli ; but as the most correct 

 observations have never given a velocity of less than nine miles a 

 second to a shooting star, it is reasonable to suppose that none have 

 ever entered our atmosphere, or, what is perhaps still more probable, 



* Prof. D. Olmsted, in a most interesting article on the subject of meteors, to be fonnd 

 in the 2Gtli volume of the Am. Journal of Science, p. 132, insists upon the difference be- 

 tween shooting stars and meteorites, and the time and attention he has devoted to the 

 phenomena of meteors give weight to his opinion. 



\ Under this head, 1 will merely note what is considered one of the best established 

 cases of the determinatioir of velocity of a meteoric stone, namely, that of the Weston 

 meteorite, the velocity of which Ur. Bowditch estimated to " ej:cecd tlirec miles a second." 

 Mr. Herrick considers the velocity somewhat greater, and writes, among other things, 

 what follows : •' 'J'he length of its path, from the observations made at Rutland, Vermont, 

 and at Weston, was at least 107 miles. This space being divided by the duration of the 

 fliglit, as estimated by two observers, viz., 30 seconds, we have for the meteor's relative 

 velocity about three and a half mil^is a second. The observations made at Wenham, Massa- 

 chusetts, are probably less exact in this respect, and need not be mentioned here. 



