204 FROM NEBULA TO NEBULA 



namely, that those asteroids whose eccentricity of orbit 

 is strongly marked are of cometary origin. 



Comets have their little brothers called meteors. 

 This is only to be expected from the very nature of the 

 case. It would be extraordinary indeed if by the explo- 

 sion of a star only one fragment, or one congeries of 

 fragments, should reach us; rather should we expect a 

 long train of scattered debris, many millions of miles in 

 length, composed of congealed globules of all sorts of 

 miscellaneous sizes. Thus Comet I, of 1861, has been 

 identified with one stream of meteors, Biela's comet with 

 another, and so on. Not only this, but there is a great 

 deal of spectroscopic evidence that comets possess a 

 chemical constitution strikingly similar to that of me- 

 teorites, which latter, of course, are only meteors that 

 have managed to reach the earth. All of these objects, 

 issuing in a fused state from the shattered hulk of their 

 parent star, and consequently more or less finely divided, 

 cool quickly in the frigid realms of space, and so remain 

 until their projectile motion is suddenly arrested, or 

 they come near the fiery furnace of the sun. When 

 either of these events occurs, the meteor explodes because 

 of the sudden expansion of its freshly heated gases with- 

 in. The reason why only the larger meteors attain the 

 earth in safety is because the friction of our atmosphere 

 is insufficient, by reason of its shallowness and lack of 

 greater density, to do more than slightly fuse their out- 

 side, as actual cases have proven. Sizable meteors that 

 do explode are known as bolides. 



Here I fancy some of my readers exclaiming : "You 

 are very inconsistent. Once you argue that flatness is 

 the best condition for stability, again, that the gibbous 

 and hemispherical shapes are, and now you champion the 

 columnar form how can you possibly reconcile these 

 contradictory statements 1" My defense is, that if there 

 be any inconsistency, the fault is Nature 's, and not mine. 

 No one, for example, will think of questioning the 

 anomalous phenomena of the gyroscope, or that a heavily- 

 tipped pestle, though laid flat on the table, will spring into 



