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Se ee be very different, so that the results would be very different 
indeed. 
** Large masses on collision probably destroy each other, produce 
fragments and vapour, which again condense. The heterogeneous 
structure is thus to a certain extent explained.” 
Here we get the birth of the meteorite, or rather, of new 
meteorites, for we are of course still as far as ever by this theory, 
from the origin of the primordial meteor. What then is the heat 
evolved by collisions at such enormous velocities? It is almost in- 
conceivable. Mr. Lockyer tells us: ‘If we take these velocities 
as representing what happens in other regions of space, and 
assume the specific heat of the meteorites to be 10, the increase in 
their temperature when their motions are arrested by impacts will 
be roughly as follows :—Velocity one mile per second, 3,000deg. 
C.; ten miles per second, 300,000deg. C.; 20 miles per second, 
1,200,000deg. C. ; 30 miles per second, 2,700,000deg. C. ; 60 miles 
per second, 10,800,000deg.”” Itis evident the heat evolved would 
be sufficient to account for all celestial phenomena of a luminous 
character, and would produce a temperature which would be 
utterly impossible to approximate in our laboratories. It is by this 
theory Mr. Lockyer accounts not only for comets and nebule, but 
for variable stars, such as Sirius and our own, and dark planets 
like our earth. He tells us, in fact, that ‘‘the existing dis- 
tinction between stars, comets, and nebule rests on no physical 
basis.” 
As the meteors draw nearer by the force of gravity into denser 
and denser swarms, the collisions become more and more frequent 
and violent, until the acme of heat is reached, producing . such 
masses of incandescent vapour as Sirius, after which comparative 
cooling would take place, under the influence of which suns of the 
second class of incandescence, such as our own sun, would be pro- 
duced. This is well illustrated by a diagramatic curve, which I 
will reproduce on the black board, showing at the ascending base 
sparse meteors, gradually drawing nearer and nearer and becoming 
more dense at the apex, then as gradually cooling as they reach 
the opposite descending course where cooling and condensation are 
comparatively complete. Such is the theory in barest outline, and 
the idea is at least a grand one. Given the two conditions, the 
existence of meteors through space, and the cumulative force of 
gravitation, and all the rest follows. But if meteors collide, may 
not the larger heavenly bodies do so also? May not suns and 
planets such as our own world, come into disastrous collision ? Mr. 
N. Lockyer tells us that in recorded time there has been nosuch a 
thing as ‘‘a world on fire,” or the collision of masses as large as 
our earth, but he adds somewhat ominously, “but the distribu- 
