200 H. A. Newton on Shooting Stars. 
earth's atmosphere in a second, and 7 the average number ina 
cubic unit of the space the earth is traversing in a given period, 
If m be the average number visible at one place ina unitof — 
time we have found above that N=10,460m. The volume ofa 4 
sphere whose radius is R is 4aR*. Let M be the number of “ 
meteoroids in a space equal to.such a sphere, then M=4anR',anl 
10460m =i (v?-++-7,?-++-6u 2), 
_4 _10460m Rv ee 
where m denotes the average number (or fraction of a number) — 
seen in one place per second. If the hourly numberis, as before 
assumed, equal to 30, then m=,1,, and M=116-2 5 
0? 
Almost every hour that a person watches, he sees, 4 
sees, flights that are yet so faint as to leave him in doubt whether 
they are shooting stars, or only illusions. We may therefore 
reasonably conclude that large numbers of shooting-stars are 
tirely invisible to the naked eye, which yet might be seen by 
telescope. 
This conclusion is verified by observation. In 1854, Messt® 
Pape and Winnecke observed? together at Gottingen for 04 
hours, on nights between the 24th of J uly and the 3d of August a 
Pape saw with the naked eye 312 shooting stars, and Winnecs 
Saw 45 in the same time with a comet seeker. The diameter ® 
the field of view is not given, but in observations at the sim 
time diameters of 53’ and 36’, with powers of 30 and 60, were tse 
comman 
’ fraction Ib 
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