322 Probable Origin and Age of the Sun . [July* 
The formation of a sun by collision is an event that would 
not be likely to escape observation if it occurred within the 
limits of visibility in space. But such an event must be of 
ver^ rare occurrence, or the number of stars visible would 
be far greater than it is. The number of stars registered 
down to the seventh magnitude, inclusive, is — according to 
Herschel— somewhere between 12,000 and 15,000, and this 
is all that can possibly be seen by the naked eye. Now, if 
we suppose each of them to shine like our sun for (say) 
100 million years, then one formed in every 7000 or 8000 
years would maintain the present number undiminished. 
But this is the number included in both hemispheres, so 
that the occurrence of an event of such unparalleled splen- 
dour and magnificence as the formation of a star or rather 
nebula— for this would be the form first assumed — is what 
can only be expedted to be seen on our hemisphere once in 
about 15,000 years. 
The absence of any historical record of such an event 
having ever occurred can therefore be no evidence whatever 
against the theory. 
Note on Sir William Thomson’s Arguments for 
the Age of the Earth. 
Sir William Thomson has endeavoured to prove the recent 
age of the earth by three well-known arguments of a 
purely physical nature : — The first is based on the age of the 
sun’s heat ; the second, on the tidal retardation of the earth’s 
rotation ; and the third, on the secular cooling of the earth. 
Argument from the Age of the Sun’s Heat . — It will be obvious 
from the frightful conflagration which would ensue, as one star ; or, thirdly, 
they would brush against one another, but not to the extent of preventing the 
stars from getting clear again.” In the latter case he considers a double star 
is formed. Mr. Stoney’s paper, though read in 1867, was not published 
till 1869. 
Mr. Herbert Spencer, in his “First Principles” (pp. 532 to 535), has also 
dire&ed attention to the fad that the stars distributed through space must 
tend, under the influence of gravity, to concentrate and become locally aggre- 
gated. Separate aggregations will be drawn towards one another, and ulti- 
mately coalesce. The result will be that the heat evolved by such collisions 
taking place under the enormous velocities acquired by gravity must have the 
effed of dissipating the matter of which they are composed into the gaseous 
state. 
Both Mr. Stoney and Mr. Spencer consider the motions of the cosmic 
masses to be due wholly to gravity, but, as we have seen, gravity alone 
cannot account for the enormous amount of energy originally possessed by 
the sun. • 
