204 THE BORDERLAND OF SCIENCE. 



forcibly to the greater giants, Saturn and Jupiter, as to 

 the lesser giants, Neptune and Uranus ; for though the 

 two former have greatly the advantage in respect of 

 attractive power, they have to deal with much more 

 swiftly moving bodies. A visitant from the celestial 

 depths would pass the orbit of Neptune with a velocity 

 of only about five miles per second, while it would cross 

 the orbit of Jupiter at the rate of about twelve miles 

 per second. Now, if this were all, there would still be 

 strong reason for doubting whether it really has been 

 by the entanglement of visitors from interstellar space 

 that meteor streams have been introduced into the 

 solar system. Remembering that the orbits of the 

 giant planets are from a thousand millions to 5,500 

 millions of miles in span, we see how enormous are the 

 chances against one of these planets occupying just 

 that short space (a few thousands of miles in length) 

 of its orbit where it could act efficiently on a body 

 crossing that orbit in its journey from outer space. 

 But there is no reason whatever why a body so arriving 

 should cross the orbit of any one of the planets. Indeed, 

 the chances are enormously in favour of its path crossing 

 the great plane of the planetary movements far away 

 from any planetary orbit. Thus, even from the con- 

 siderations already taken into account, we see that 

 either there must be an inconceivably enormous number 

 of visitants from outer space, or the giant planets 

 would have but a poor chance of entrapping even a few 

 meteors ; whereas we know that the number of meteor 

 streams existing within the solar system must be counted 



