1904 - 5 .] On Prof. Seeliger’s Theory of Temporary Stars. 547 
“ backwardation,” as Sir Norman Lockyer appropriately calls it, 
because it reveals a sequence of phenomena exactly opposite to 
what we comprehend as the natural evolution of a cosmic body, — 
are indeed features well known to students of this problem. 
We notice, then, that Seeliger’s ingenious hypothesis can be made 
to respond to a number of observed facts if the circumstances are 
duly considered under which the supposed collision between a dark 
body and a cosmic cloud may occur. An effort has been made 
in this communication to emphasise the important rdle played by 
the star’s gravitational force, and to show that the motions of 
incandescent matter generated by the star’s attraction are probably 
sufficient, from a qualitative as well as a quantitative point of view, 
to explain the peculiarities of the Nova spectrum, and also to 
account for the extraordinary process of evolution noticed in 
temporary stars. 
One of the conclusions reached in this paper is that, as an effect 
of one-sided collision, the cosmic body may become surrounded 
by a revolving ring of nebular matter. Before the collision, 
neither the star nor the nebula were supposed to possess a rotational 
momentum. But the mere fact of a meteoric swarm impinging upon 
the star leads to the conclusion that a permanent ring of meteoric 
matter may be formed, the constituents of which revolve with 
orbital velocities round the star nucleus. May not this conclusion 
perhaps assist us in explaining the origin of the rotation of our 
own solar system ? It is well known that Laplace, in his 
celebrated hypothesis, assumed rotation as a pre-existing quality 
of the solar nebula. He clearly recognised, what had escaped the 
less mathematical genius of Kant, that rotation could not have 
been generated by the internal motions of the contracting matter ; 
that only an external agency could have introduced it into our 
system. Laplace made no attempt to define this agency : he boldly 
assumed its primeval operation, and started his hypothesis from 
the moment when rotation had been impressed upon the vast 
cosmic cloud from which our present system has gradually been 
formed. No doubt, our attempts to grasp the evolution of the 
natural world can only begin from a certain stage ; unconceivable 
creation stands at the beginning of the cosmos. Laplace’s assump- 
tion of original rotation is therefore certainly justified, and must be 
