6io THE POPULAR SCIENCE MONTHLY. 



yoTi know, was discovered by the effect of its pulling force on 

 another planet, the latter being deflected from its normal course. 

 When this pulling force is not counterbalanced by other forces, 

 or when the objects pulled have not sufficient resisting power, 

 they fall into each other. Thus, this earth is daily causing a bom- 

 bardment of itself by drawing smaller bodies — meteorites — to it ; 

 twenty millions of which, visible to the naked eye, fall on an aver- 

 age into our atmosj)here in each twenty-four hours, and of those 

 visible through the telescope, four hundred millions are computed 

 to fall within the same period. Mr. Lockyer has recently given 

 reasons for supposing the luminosity of nebulae, or of many of 

 them, is due to collisions or friction among the meteorites which 

 go to form them ; but his paper on the subject is not yet pub- 

 lished. 



What is commonly called centrifugal force does not come from 

 nothing ; it depends uiDon the law that a body falling by the influ- 

 ence of attraction, not upon, but near to, the attracting body, 

 whirls round the latter, describing one of the curves known as 

 conic sections. Hence, a meteorite may become a planet or satel- 

 lite (one was supposed to have become so to this earth, but I be- 

 lieve the observations have not been verified) ; or it may go off in 

 a parabola as comets do ; or, again, this centrifugal force may be 

 generated by the gradual accretion of nebulous matter into solid 

 masses falling near to, or being thrown off from, the central nu- 

 cleus, the two forces, centrifugal and centripetal, being antago- 

 nistic to each other, and the relative movements being continuous, 

 but probably not perpetual. Our solar system is also kept in its 

 place by the antagonism of the surrounding bodies of the cosmos 

 pulling at us. Suppose half of the stars we see — i. e., all on one 

 side of a meridian line — were removed, what would become of our 

 solar system ? It would drift away to the side where attraction 

 still existed, and there would be a wreck of matter and a crash 

 of worlds. It is very little known that Shakespeare was acquainted 

 with this pulling force. He says, by the mouth of Cressida — 



" But the strong base and building of my love 

 Is as the very center of the earth 

 Drawing all things to it " — 



a very accurate description of the law of gravitation, so far as 

 this earth is concerned, and written nearly a century before New- 

 ton's time. 



But in all probability the collisions of meteorites with the 

 earth and other suns and planets are not the only collisions in 

 space. I know of no better theory to account for the phenomena 

 of temporary stars, such as that which appeared in 1866, than that 

 they result from the collision of non-luminous stars, or stars pre- 

 viously invisible to us. That star burst suddenly into light, and 



