50) REPORT-—1905. 
This is not the time to pursue these considerations further, but enough 
has been said to show that the Nebular Hypothesis cannot be considered 
as a connected intelligible whole, however much of truth it may contain. 
Tn the first theory which I sketched as to the origin of the sun and 
planets, we supposed them to grow by the accretions of meteoric wan- 
derers in space, and this hypothesis is apparently in fundamental disagree- 
ment with the conception of Laplace, who watches the transformations 
of a continuous gaseous nebula. Some years ago a method occurred to me 
by which these two discordant schemes of origin might perhaps be recon- 
ciled. A gas is not really continuous, but it consists of a vast number of 
molecules moving in all directions with great speed and frequently coming 
into collision with one another. Now I have ventured to suggest that a 
swarm of meteorites would, by frequent collisions, form a medium endowed 
with so much of the mechanical properties of a gas as would satisfy 
Laplace’s conditions. If this is so, a nebula may be regarded as a quasi- 
gas, whose molecules are meteorites. The gaseous luminosity which un- 
doubtedly is sent out by nebulze would then be due only to incandescent 
gas generated by the clash of meteorites, while the dark bodies themselves 
would remain invisible. Sir Norman Lockyer finds spectroscopic evi- 
dence which led him long ago to some such view as this, and it is certainly of 
interest to find in his views a possible means of reconciling two apparently 
totally discordant theories.'_ However, Ido not desire to lay much stress 
on my suggestion, for without doubt a swarm of meteors could only 
maintain the mechanical properties of a gas for a limited time, and, as 
pointed out by Professor Chamberlin, it is difficult to understand how 
a swarm of meteorites moving indiscriminately in every direction could 
ever have come into existence. But my paper may have served to some 
extent to suggest to Chamberlin his recent modification of the Nebular 
Hypothesis, in which he seeks to reconcile Laplace’s view with a meteo- 
ritic origin of the planetary system.? 
We have seen that, in order to explain the genesis of planets according 
to Laplace’s theory, the rings must be ill-balanced or even broken. If the 
ring were so far from being complete as only to cover a small segment of 
the whole circumference, the true features of the occurrences in the births 
of planets and satellites might be better represented by conceiving the 
detached portion of matter to have been more or less globular from the 
first, rather than ring-shaped. Now this idea introduces us to a group 
of researches whereby mathematicians have sought to explain the birth of 
planets and satellites in a way which might appear, at first sight, to be 
fundamentally different from that of Laplace. 
The solution of the problem of evolution involves the search for those 
persistent or stable forms which biologists would call species. The species 
of which Iam now going to speak may be grouped in a family, which 
1 Newcomb considers the objections to Lockyer’s theory insuperable, See p. 190 
of The Stars, John Murray, London, 1904. 
2 See preceding reference to Chamberlin’s Paper, 
