640 THE POPULAR SCIENCE MONTHLY. 



our own solar system than about any other in our own universe, and 

 it also possesses for us a greater practical and personal interest than 

 any outside jiortion of the galaxy. Nobody can pretend to be pro- 

 foundly immersed in the internal affairs of Sirius or of Alpha Cen- 

 tauri. A fiery revolution in the belt of Orion would affect us less than 

 a passing finger-ache in a certain single terrestrial baby of our own 

 household. Therefore I shall not apologize in any way for leaving 

 the remainder of the sidereal universe to its unknown fate, and con- 

 centrating my attention mainly on the affairs of that solitary little, 

 out-of-the-way second-rate system, whereof we form an inappreciable 

 portion. The matter which now composes the sun and its attendant 

 bodies (the satellites included) was once spread out, according to La- 

 place, to at least the farthest orbit of the outermost planet — that is 

 to say, so far as our present knowledge goes, the planet Neptune. 

 Of course, when it was expanded to that immense distance, it must 

 have been very thin indeed, thinner than our clumsy human senses 

 can even conceive of. An American would say, " too thin " : but I put 

 Americans out of court at once as mere iireverent scoffers. From the 

 orbit of Neptune, or something outside it, the faint and cloud-like 

 mass which bore within it Csesar and his fortunes, not to mention the 

 remainder of the earth and the solar system, began slowly to con- 

 verge and gather itself in, growing denser and denser but smaller and 

 smaller as it gradually neared its existing dimensions. How long 

 a time it took to do it is for our present purpose relatively unimpor- 

 tant : the cruel jihysicists will only let us have a beggarly hundred 

 million years or so for the process, while the grasping and extrava- 

 gant evolutionary geologists beg with tears for at least double or even 

 ten times that limited period. But at any rate it has taken a good 

 long while, and, as far as most of us are personally concerned, the 

 difference of one or two hundred millions, if it comes to that, is not 

 really at all an appreciable one. 



As it condensed and lessened toward its central core, revolving 

 rapidly on its great axis, the solar mist left behind at irregular inter- 

 vals concentric rings or belts of cloud-like matter, cast off from its 

 equator ; which belts, once moi^e undergoing a similar evolution on 

 their own account, have hardened round their private centers of 

 gravity into Jupiter or Saturn, the Earth or Venus. Eound these 

 again, minor belts or rings have sometimes formed, as in Saturn's 

 girdle of petty satellites ; or subsidiary planets, thrown out into 

 space, have circled round their own primaries, as the moon does 

 around this sublunary world of ours. Meanwhile, the main central 

 mass of all, retreating ever inward as it dropped behind it these 

 occasional little reminders of its temporary stoppages, formed at last 

 the sun itself, the main luminary of our entire system. Now, I won't 

 deny that this primitive Kantian and Laplacian evolutionism, this 

 nebular theory of such exquisite concinnity, here reduced to its sim- 



