410 POPULAR LECTURES AND ADDRESSES. 



considering, each globe had a transverse velocity 

 of three-quarters (or anything more than 71) of a 

 kilometre per second, they would just escape 

 collision, and would revolve in ellipses round their 

 common centre of inertia in a period of one year, 

 just grazing each other's surface every time they 

 came to the nearest points of their orbits. 



If the initial transverse velocity of each globe be 

 less than, but not much less than, 71 of a kilometre 

 per second, there will be a violent grazing collision, 

 and two bright suns, solid globes bathed in flaming 

 fluid, will come into existence in the course of a 

 few hours, and will commence revolving round their 

 common centre of inertia in long elliptic orbits in a 

 period of a little less than a year. Tidal inter- 

 action between them will diminish the eccentricities 

 of their orbits, and if continued long enough will 

 cause the two to revolve in circular orbits round 

 their centre of inertia with a distance between 

 their surfaces equal to 6*44 diameters of each. 



Suppose now, still choosing a particular case to 

 fix the ideas, that twenty-nine million cold, solid 

 globes, each of about the same mass as thejnoon, 



