104 THE WONDERFUL CENTURY. CHAP. xi. 



universe have arisen from the aggregation of widely 

 diffused solid particles, molecules, or atoms, whose com- 

 ing together under the influence of gravitation produces 

 heat, incandescence, and sometimes elemental vaporiza- 

 tion, rather than from a primitive cosmic vapor from 

 which solid masses have been formed by cooling and con- 

 traction. Everywhere we become aware of these solid 

 masses of various sizes occupying the spaces around us. 

 The rings of Saturn are composed of such solid particles 

 in a state of unusual condensation. The vast ring of the 

 minor planets indicates -probably the existence there of 

 millions of smaller invisible bodies forming a stream of 

 meteors, analogous to some of those which cross our 

 orbit, but which are composed of much smaller bodies 

 since none of them are independently visible. Then 

 we have the comets, consisting of a dense swarm of such 

 meteors, whose frequent collisions may produce the 

 luminous gases indicated by their spectra. Yet further, 

 the strange zodiacal light, extending from the sun be- 

 yond the earth's orbit, is well explained as due to the 

 light reflected under favorable conditions from the 

 countless streams of meteors, ever increasing in density 

 as they approach the sun. 



In its wider application to the stellar universe, the 

 same theory serves to explain phenomena once supposed 

 to be radically distinct. There is now known to be a 

 perfect gradation from the faintest and least condensed 

 nebulas to the most brilliant stars, and these are all ex- 

 plained, on what is termed the meteoritic hypothesis, as 

 being different stages in the aggregation of meteoritic 

 matter everywhere and always going on. From the 

 faintest diffused nebulae we pass to those which exhibit a 



