eyecare oe 
be 
i 
* 
: 
«3 
ba. 
’ 
ie 
a Be ape oo Re ee ae oR eee a | ee yi 
a LAS thls Odea” Te Cea 
H. A. Newton on Shooting Stars, 207 
This estimate, and these numbers, taken strictly imply a mean 
velocity greater than that of a parabolic orbit. The character 
of the data does not allow the argument to be pressed. Yet we 
must regard as almost certain (on the hypothesis of an equable 
distribution of the directions of absolute motions), that the mean 
velocity of the meteoroids exceeds considerably that of the 
earth; that the orbits are not approximately circular, but 
resemble more the orbits of the comets. 
. Number of meteoroids in the space which the earth is travers- 
iny—We have found that, of the space through which the earth 
18 moving, a volume equal to that of the earth (atmosphere 
4 
_ included), contains a mean number of meteoroids expressed by 
equation 
v 
R 
M=116-2 tp0eie) 
55 
Ah this equation v is the mean relative velocity of the meteor- 
Olds. If their absolute velocities were equal, and the points 
_ om which they come uniformly distributed over the heavens, 
_ Weshould evidently have 
1 S } ; yi2 
a on . of (v2-L-v!2 — 2vv' cosw)? sin ada—o- 
For v we may use as an approximation the mean absolute 
“Nelocity. If v=o’, then v= 4y, If v'=v/2, then V = jv. 
_ *f grouped according to some law, is altogether probable. But 
8 Velocit 
rc ~ they are not grouped closely about the earth’s orbit. 
__ These bodies cannot be regarded as the fragments of former 
‘ Worlds. They are rather the materials from which the worlds 
a forming, If astronomy furnishes any measure of their total 
the nv’ ™9Y therefrom obtain some idea, rude though it be, of 
Thean mass of the individuals. | 
