72 TT. C. CHAMBERLIN 
and developing by secular cooling. The argument is equally 
cogent against an evolution from a meteoroidal spheroid con- 
trolled by the laws of convective equilibrium, such, for example, 
as that made the subject of investigation by Darwin in his 
memoir: ‘On the Mechanical Conditions of a Swarm of 
Meteorites and on Theories of Cosmogony.”’ 
The results point to an unsymmetrical distribution of matter 
and of momentum. It should go without saying that we assume 
a nebular origin in the broad sense of the term, but the inquiry 
seems to show that the original form of the nebula and the 
mode of its development are to be sought on new lines. The 
foregoing data seem to constitute criteria of a rather rigorous 
nature to which a working hypothesis must conform. They are 
thereby aids in the construction of a tenable hypothesis. They 
seem to require the assignment of some mode of origin by 
which the peripheral portion of the system acquired all but a 
trivial part of the moment of momentum, while it possessed but 
a trivial part of the mass. The first suggestion of these con- 
clusions was the possible formation of the system by the collision 
of a small nebula upon the outer portion of a large one, the 
smaller one having necessarily a high ratio of momentum to 
mass, while the larger one may have had little or no rotatory 
momentum, or even an adverse rotation. The low degrees of 
ellipticity of the present orbits seem to present grave difficulties 
in the framing of a consistent hypothesis of origin along this 
line, but these may not prove insuperable. 
The results also naturally turn thought anew toward axwiing 
nebula for an exemplification of the evolution of the solar system. 
It is not a little significant that of the thousands of nebula now 
known no one, I believe, closely represents the annular process ; 
certainly none represents the secondary annulation coincident 
with the primary. To bring the current hypothesis into con- 
sistency with observed nebular states, it seems necessary to 
assign it to so late a stage of concentration and to such small 
dimensions as to be beyond observation——at most, a hypothetical 
resort. 
