18 



Course 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, 

 l,'200,000deg. 0. ; 30 miles per second, 2,700,000deg. C. ; 60 miles 

 per second, 10,800,000deg." It is 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 thi« 

 tbeory Mr. Lockyer accounts not only for comets and nebulae, 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 nebulae 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 no such 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- 



