40 Mr. G, J. Stoney [Feb. 14, 



WEEKLY EVENING MEETING, 



Friday, February 14, 1879. 



C. William Siemens, Esq. D.C.L. F.R.S. Vice-President, in the Cbaii". 



G. Johnstone Stoney, Esq. M.A. r.K.S. 



The Story of the November Meteors. 



[As some readers may wish to consult the original investigations referred to 

 in this lecture, a list of them is given in a postscript at the end.] 



METEOBS AS THEY APPEAR IN THE EARTH's ATMOSPHERE. 



When observers band together to watch every quarter of the sky, and 

 to keep on the look-out through the whole night, the number of 

 meteors that present themselves is very great. In this way it has 

 been ascertained that upwards of thirty on the average, which are 

 conspicuous enough to be seen without instruments, come within the 

 view of the observers stationed at one locality. And it is computed 

 that telescopic meteors must be about forty or fifty times as numerous 

 as those visible to the naked eye. 



These results may be obtained from observations made at one 

 station ; but when concerted observations are carried on at different 

 stations, several other facts of interest come to light. By simultaneous 

 observations at distant stations, it has been discovered that the height 

 of meteors above the surface of the earth usually ranges from 120 

 down to twenty miles, the average height being about sixty miles ; 

 that the direction of their flight is towards the earth, either in a 

 vertical or in a sloping direction ; and that their speed in most cases 

 lies between thirty and fifty miles a second. 



We thus arrive at the conclusion that visible meteors are phenomena 

 of our own atmosphere ; and as the atmosphere reaches a height, at 

 most, of 150 miles, and is, therefore, but a thin film over so vast a 

 globe as the earth, it is obvious that the spectators at any one place 

 can see only a very small portion of the meteors which dart about 

 through all parts of this envelope. After making allowance for this, 

 we are forced to conclude that no fewer than 300 millions of these 

 bodies pass daily into the earth's atmosphere, of which about seven 

 millions and a half are large enough to be seen with the naked eye on 

 a clear night, and in the absence of the moon. 



From the direction and swiftness of their flight, it is manifest that 

 meteors are visitors from without. They plunge into our atmosphere, 



