ADDRESSES 51 
also tally with the great events of cosmic evolution of which 
the origin of our little system was but a trivial part, however 
important to us. But before considering these more general 
relations, let us look to the terms of the hypothesis we offer 
to better fit the facts of the case. 
It has been implied already that the genesis of our sun— 
and of course the genesis of stars in general—is not regarded 
as a part of our immediate task. The evolution of the sun is 
held to be an earlier event. The birth of the present planetary 
system is assigned to an intercurrent incident, a later episode 
in the sun’s history. This is one of the distinctive features of 
the new hypothesis. This later genesis of the planets seems 
required because the rotational features of the sun and the 
revolutionary features of the planets are so out of accord as to 
imply origins under different conditions. This is equally im- 
plied by the discordant ratio of mass to momentum. The sun 
holds about 745 out of 746 parts of the total matter of the 
solar system, while it only carries about 2 per cent of its 
moment of momentum. These discordant features lead to the 
conviction that a new agency came in, after the original for- 
mation of the sun, and gave to a very small fraction of the 
solar matter—after it had been drawn ont from the sun— 
a special endowment of momentum, This action is assigned 
to so simple an event as the passing of a star (or other mas- 
sive body) near the sun, calling forth a very small fraction 
of his mass and endowing it richly with momentum from the 
visitor's own store, As there are a hundred million or more 
stars in the heavens moving in diverse directions and at vary- 
ing rates, much like the molecules of a gas, many close 
approaches and some collisions may be regarded as inevitable, 
and so our appeal is made to an event of high probability. Let 
it be noted that no appeal is made just here to actual collisions 
of stars, but merely to approaches of such degrees that there 
must have been millions more of them than of actual collisions. 
The mode of action of the passing star in calling forth a 
trivial fraction of the sun’s substance and giving it high mo- 
mentum in orbital form, rests upon an extension and adapta- 
tion of a principle enunciated long ago by Roche and con- 
firmed by Maxwell and others. It was shown by Roche that 
if a secondary body were made to approach its primary, it 
would be torn asunder by the differential attraction of the 
