1 66 LIGHT SCIENCE FOR LEISURE HOURS. 



the case, and in such marked degree that no streamer 

 can be traced at all to a distance of more than five or 

 six diameters of the sun from him. In this we have 

 proof positive, that there is a marked falling off in the 

 illumination of the meteor stream on either side of the 

 sun's place, wherefore (not as a doubtful inference, but 

 with absolute certainty) the parts thus much more faintly 

 illuminated are much farther from the sun. 



No other argument should be necessary, but so 

 slowly are considerations of this kind attended to, that 

 it may be as well to strengthen the evidence which,, 

 rightly apprehended, is irresistible. Here, then, is 

 another argument": 



If meteor systems lying as far as the earth's orbit 

 from the sun, or even no farther from him than the 

 orbits of Venus or Mercury, could be seen during total 

 eclipse, the chances would be greatly in favour of such 

 a system being seen as a thwart streak not passing 

 directly (in appearance) behind the sun's disc, but 

 lying above or below or on either side of that disc. 

 The meteor stream might be compared to the orbit of 

 a planet, except that all the planets have orbits nearly 

 in the same plane as the earth's, while the meteor 

 systems cross the plane of the earth's orbit at all 

 possible angles. Now even in the case of the planets 

 Venus and Mercury, the orbits, though lying not far 

 from the plane of the earth's path, lie always, except 

 for a few days in December and June, in the case of 

 Venus, and in November and May, in the case of 

 Mercury, above or below the sun's disc as seen from 



