546 Transactions. — Miscellaneotis. 



8. All impacts brought about in this way by deflection will 

 be of a grazing character ; consequently nearly all stellar col- 

 lisions will be of a grazing character. 



9. The average velocity of stars at impact will be hundreds 

 of miles a second, and in many cases thousands. The average 

 " proper motion " will not appreciably affect the final velocity. 

 Thus a proper motion of ten miles will only add one mile a 

 second to a colliding velocity (velocity acquired by attrac- 

 tion) of one hundred miles a second. 



10. A mere graze of the atmospheres of stars obviously will 

 not cause them to coalesce, nor will a slight graze of the stars 

 themselves. As a mean result, when more than a third of 

 each of two equal bodies collide, coalescence will ensue, but 

 this will depend on the original proper motion. Were nine- 

 tenths of 1830 Groombridge to collide with a similar star the 

 remaining tenth would not be stopped in its course ; it would 

 pass on in space, the bulk of the two stars temporarily 

 coalescing and then dissipating into space. 



11. The effect of the collision will be to intensely heat the 

 colliding parts. 



Partial Impact. 



12. The heating effect of a graze of two stars, of two star- 

 clusters, or of two nebulae, or even of a star plunging through 

 a star-cluster, will not appreciably extend to the parts not 

 colliding. To emphasize this fact such impacts have been 

 called "partial." 



13. " Partial impacts " generally result in the formation of 

 three bodies. The fraction of each star, lying in the path of 

 the otber, which actually collides, and whose momentum will 

 be nearly or quite destroyed, will be cut off from the rest of 

 the star ; they will coalesce and remain behind, whilst the 

 two cut stars pass on in space. 



14. Partial impacts of a third of two equal stars having 

 considerable original proper motion would make of the 

 two impacting orbs three equal bodies : two of them 

 would travel on in space in opposite directions ; the third 

 would merely revolve without any motion of translation. If 

 there had been no proper motion the three bodies would have 

 coalesced. If less than a third be cut off from each, the two 

 bodies become three bodies orbitally connected. 



15. The temperature produced by an impact depends on 

 the velocity destroyed and on the chemical constitution of 

 the colliding bodies. High velocities and heavy molecules 

 both tend to produce high temperatures. Consequently the 

 temperature depends upon the velocity destroyed and on the 

 molecular constitution, and not upon the amount of the graze. 

 Were one-tenth or one-hundredth grazed off the impacting 



