132 
[March, 
The Heat of the Sun. 
that of Conical Refraction are considered as having fixed 
the Gravitation and Undulatory Theories respectively on a 
firm basis. It happens that the Meteoric Theory has also 
its nredidtion. Owing, however, to its nature we are and 
shaU be unfortunately unable to verify it. The prediction is 
nothing more nor less than that of the end o ou . r P ar J e ^ 
system, and in fact of the universe. Moons will fall into 
planets, planets into suns, and suns into other suns, and 
the last only one mighty sun will remain, this is the 
to which all must come. . 
In taking leave of this theory I cannot omit to mention 
one important point which I do not think has been raise 
before, and which, so far as I am aware, has not attracted 
the notice of its supporters. It will be seen that one of its 
assumptions is that the central body is gradually, a' though 
very slowly, attrafting the revolving bodies neaiei to ltselk 
Extending^ this idea very slightly, we have that the plane cs 
adting as central bodies ought to be ^ gradually attracting 
their satellites. This point has been fully and ably worked 
out bv Mr. G. H. Darwin, and he has come to the conclusion 
that the Moon has been, and still is, gradually receding from 
the Earth. Upon this point, therefore, theory and obseiva- 
tion seem to be opposed to each other, and we shall be gla 
to see the explanation of the supporters upon it. 
The Contraction Theory. 
In the above statement of the Meteoric Theory it is 
pointed out how comparatively small an addition to the 
bulk of the Sun is able to support the loss of eneigy which 
he suffers. But although undoubtedly the amount which 
has fallen during historic times is small compared to the 
immense bulk of the Sun, yet when we consider geologic 
times the case is different. 1 he additions which the Sun 
has received during these times must have caused a giea 
change in the periods of planetary revolution ; and it is 
hardly possible to avoid the conclusion that, if such is taking 
placef some evidence of it would have been found ere this 
Considerations somewhat of this natuie induced the gie 
German philosopher Helmholtz to discard the theory, and 
to propose in its stead one founded on the heat given out by 
the P contra&ing of the body of the Sun, and hence called 
the Contraction Theory. Speaking of this theory in a recent 
ledture at New York, Prof. Young, of \eimont, sa\ s . 
“ It is the one held by most scientific men and is one which 
I think will be found more than halt tiue. Without 
