228 COSMOGONIC HYPOTHESES. 



assumption lias no foundation in nature, and is so improbable 

 that it cannot be accepted without proof. I.ockyer's meteoritic 

 hypothesis started with a swarm of soHd bodies, meteorites, 

 which by their colHsions gave rise to a nebula, which then fol- 

 lowed more or less closely the developments suggested by the 

 Laplacian theory, iDut the spectroscopic evidence on which it 

 rested has since been proved to be devoid of foundation. 



Although many cosmogonic hypotheses have been imagined, 

 I wisli to shmv that another can be added to them ; its chief 

 merit being that it takes into account the few facts of observation 

 which are available to-day. The hypothesis is compounded of 

 the planetesimal hypothesis of Chamberlin and Moulton, and 

 the radiation theory of Arrhenius with the addition of an explo- 

 sive element suggested by the nuitations of uranium-radium- 

 helium. 



The primordial stuff out of which the universe is made is in 

 the form of meteors. Aggregations of meteors are caused by 

 collisions and gravitation. These aggregations increase in size, 

 forming, firstly, cometary bodies ; secondly, planetary bodies ; 

 thirdly, sun-type bodies. Growth is continuous in one direction 

 in all these bodies, so that a cometary body by the addition of 

 more meteorites can pass into a planetary body, and a planetary 

 body similarly into a sun-type body, but a sun-type body cannot 

 increase in size indefinitely, as a time comes when it will disrupt 

 with explosive force. A cometar}^ body is a loose aggregation 

 of meteors. A planetary body is a solid body in which the forces 

 of solidification and cohesion are at a maximum. A sun-type 

 body is a liquid body, of which the sun is a prototype. The 

 reverse process cannot take place ; thus a sun-type body cannot 

 shed meteorites and so lose matter until it becomes a planetary 

 body, etc. Under certain circumstances such as the near presence 

 of a large mass, a cometary aggregation can, however, be dissi- 

 pated, but this is an indirect effect which does not concern us 

 here. All three classes of bodies can radiate substances in the 

 form of electrons, although at vastly different rates, so that they 

 can pass from the solid or liquid to the gaseous state, which is 

 and will be called here the stellar state, and from the gaseous or 

 stellar state to the final form — the ne1:)ulous state. The stellar 

 state is the first step in the degradation of atomic matter. 



It has to be considered how this liypothesis fits the facts. 

 Clausius has taught us that the end of the universe as an abode 

 of life or available energy will be reached when entropy* becomes 

 a maximum, and that it does tend to such a maximum. This 

 conclusion is not contradicted, it is only enlarged so as to include 

 in the available energy the enormous stores of power contained 



* In Thermodynamics "' entropy " means a property of a body ex- 

 pressed as a mathematical quantity which remains constant when a gas 

 changes its volume or does work without any heat entering or leaving it. 

 but which, if a small amount of heat enters or leaves the body, is increased 

 or diminished proportionately to this amount divided by tlie absolute tem- 

 perature. 



