1912] The Ottawa Naturalist. 55 



As we have seen, the whole tendency of stellar evolution is 

 towards a loss of energy, a cooling down, and eventually all the 

 stars we now see will become dead and invisible; and, unless 

 there is some means of replenishing this energy , the whole universe 

 will get to one level of coldness, invisibility, and deadness. Do 

 we know any means by which such a dead system may be revivi- 

 fied? So far as any energy from within each body is concerned, 

 no. Nevertheless, each of these bodies contains an incon- 

 ceivablv vast store of kinetic energy, energy of motion. They are 

 all moving in all directions with velocities varying up to about 

 200 miles per second on the average about ten miles a second. 

 Although they are relatively small as compared with the vast 

 distances between them, nevertheless in the hundred million 

 or so of stars in the visible universe, it is certain that some pairs 

 will come within range of each other's attraction, will be drawn 

 towards each other with constantly increasing velocity and 

 will, under certain conditions, collide either directly or with 

 grazingi contact. What will then happen? We know what 

 would happen if two projectiles from modern cannon, each 

 moving with a velocity less than half a mile per second and 

 weighing less than a ton were to collide. They would be prac- 

 tically destroyed and made intensely hot. We cannot conceive 

 the destructive effects of the collision of two bodies, billions 

 upon billions of times as massive as our cannon balls, and 

 moving, as they would be at the instant of collision, about a 

 thousand times as fast. They would certainly be entirely 

 vaporized with explosive violence and scattered over an enor- 

 mous space and we would have again a nebula which would 

 undoubtedly pass through the process of evolution already 

 described. 



This is a verv fascinating hypothesis, that the universe 

 contains in itself the forces which will keep it in existence, in 

 undiminshed glorv- Although we do know that such collisions 

 will occur and have occurred, we do not know whether they are 

 of sufficient frequency to renew the loss of energy constantly 

 going on. That such collisions occur is attested by the appear- 

 ance of new stars (Novae) which come from time to time. The 

 most notable in recent years (1907) was in the constellation 

 Perseus. It was discovered by a Dr. Anderson of Edinburgh, 

 who only a short time previously discovered a less striking Nova; 

 it suddenly appeared where no star had been previously, blazed 

 up in the most spectacular manner so that in a few hours it was 

 brighter than any star in the sky, and then nearly as rapidly 

 faded. It now has the appearance and gives the spectrum of 

 a nebula. There can hardly v " 3 anv doubt that these novae 



