346 THE POPULAR SCIENCE MONTHLY. 



this mass into the attracting spheres of surrounding stars, and thus 

 beyond the possibility of return. 



It may be proper, here, to point out the modus operandi by which 

 such systems reach the state of quiescence alluded to above, which is, 

 substantially, as follows: 



The planets absorb their satellites by first converting them into 

 fragmentary rings as Saturn has already transformed two of his. 

 These rings graduall}' approach the planets, till finally they fall upon 

 their surfaces, and become part of them ; while the planets themselves 

 are approaching their primaries to succumb to a like fate. 



Having absorbed their planetary attendants, and having cooled off 

 so as to become cold, dark bodies, like the earth, they enter the sphere 

 of each other's sensible attraction, and begin to approach with continu- 

 ally increasing velocity, till finally they meet, each arriving at the point 

 of contact with a velocity of from 400 to 500 miles a second, depend- 

 ing on their mass and density. 



Of the heat generated by such a collision, we can have no adequate 

 conception. It may, however, be calculated, and written down in ther- 

 mometric degrees ; 1 still the figures are meaningless to us except as 

 representing an inconceivable intensity of heat. 



It may be stated as so many thousand times the heat generated by 

 the explosion of an equal weight of gunpowder, still we are unable to 

 form an idea of the unit of measure here given. 



If the doctrine of the "correlation and conservation of forces" be 

 true, then the heat thus generated, if it could all be applied in the form 

 of moving force to these two bodies while yet intact, should be suffi- 

 cient to throw them back again to the points at which their motions 

 began to be accelerated, if there were no resistance ; but, owing to the 

 resistance met with, they will not rebound fully to those points. 3 



It will not, however, be expended in that manner, but in expanding 

 the entire mass of these two globes into a thin, nebulous vapor ; large 

 portions of which, most probably, will be thrown out beyond the sphere 

 of sensible attraction of that which remains, and into those of the sur- 

 rounding stars. 



This great probability will much resemble a certainty when we come 

 to subject the question to the following speculative illustration : 



1 Assuming the average specific heat of cosmic matter to be one-fifth that of water, 

 then the calculated temperature due to a velocity of 400 miles a second is equal to nearly 

 450,000,000 Fahr., or 250,000,000 Centigrade. 



2 It may be well to remark just here that the resistance here spoken of is assumed to 

 be caused by the so-called ether of space, through which all bodies must move. Now, 

 this resistance may be due to the inertia of the ether alone, in which case we must sup- 

 pose that the ether is perfectly fluent, and receives a kind of mass-motion from the bod- 

 ies moving through it. Or, on the other hand, we may conceive it to be a friction between 

 the moving body and the ether. In this case the ether will be given a wave-motion of 

 some kind, while the ponderable matter acquires a molecular motion. In either case 

 there will be no motion lost. 



