A SWAEM OF METEORITES, AND ON THEORIES OF COSMOGONY. 
33 
point one place to the right in the last four rows of entries it becomes kilogrammes, 
one more and it becomes tonnes, and another, thousands of tonnes, and so on. 
IV.— ^Table of Results. 
The meteorites weigh 3-|- grammes, and have the density of iron. The swarm 
extends to ag being Earth’s distance from Sun. 
Distance from 1 r _ 
centre i Oq ~ 
Sun. 
Asteroids. 
Saturn. 
16 
Urauus. 
24 
Xeptune. 
44i| 
0 
2-55 
7-66 
12-77 
19-2 
32 
Velocity of mean j 
square in kilo- = 
metres per sec. J 
5-37 
5-37 
5-37 
5-37 
5-37 
4-85 
412 
2-93 
0 
Mean free patli, — = 
«o 
L kilom. = 
•00028 
41,600 
•00038 
57.000 
•00157 
233,000 
•00511 
760,000 
•00900 
1,340,000 
■0122 
1,810,000 
•0199 
2,960,000 
■0552 
8,210,000 
00 
GO 
Mean free time, 1 y_ 
in days J 
•097 
•133 
•545 
1-78 
313 
4-70 
9-02 
35-17 
1 
Criterion, ~ — 
L 
•0000167 
•0000832 
•000195 
•000278 
•000387 
•000709 
•00279 
GO 
A 
Criterion, — = 
a 
1 
•0000113 
•0000295 
-0000633 
•0000895 
•000111 
•000174 
•000497 
00 
The incidence of the several planets in the scale of distance is roughly indicated by 
the names written above. 
The criteria show that, if the meteorites weigh 3|- kilogrammes, the collisions are 
frequent enough, even beyond the orbit of Neptune, to allow the kinetic theory of 
gases to be applicable for such problems as are in contemplation. For, when rja = 32, 
the two criteria (with decimal point shifted one place to the right) are ’028 and '005, 
both small fractions. But, if the meteorites weigh 3| tonnes, the criteria cease to he 
very small, about r/a = 24. If they weigh 3125 tonnes, the applicability will cease 
somewhat beyond where the asteroids now are. 
I conclude, then, from this discussion that we are justified in applying hydro- 
dynamical treatment to a swarm of meteorites from which the solar system originated, 
even in the earliest stages of the history of the swarm. 
This discussion has, of course, no bearing on the fundamental hypothesis that 
meteorites can glance from one another on impact with a virtually high degree of 
elasticity; nor does it do anything to justify the assumption that a swarm wall consist 
approximately of a quasi-isothermal nucleus with a quasi-adiabatic layer over it. 
This latter assumption I have been led to the considerations to which -we now pass. 
MDCCCLXXXIX. —A. 
F 
