THE EARTH IN METEORIC SHADOW. 151 



The theory is very ingenious, and has the advantage 

 of being easily understood. It has therefore been 

 quoted again and again, by persons unfamiliar with 

 astronomy ; it has done duty in newspaper science 

 almost every year since it was first propounded. Even 

 *3o late as 1879, M. de Fonvielle, editor of La Nature, 

 presented it, not as a doubtful theory, but (after the 

 manner which is characteristic, and I cannot but think 

 a characteristic defect of French popular science teach- 

 ing) as a known fact, which his readers were to accept 

 because he said it * Je vous le dis MOI,' he seems to 

 say ; ' The chilliness is due to the fact that the earth 

 passes behind a ring of asteroids, which absorbs a 

 portion of the sun's warmth, due to us while he re- 

 mains above the horizon. The temperature does not 

 resume its ascensional movement until the annual 

 rotation has carried our earth from the shadow of the 

 multitude of small planets which is always projected 

 on the same point of our orbit.' 



Now, when Erman first advanced this theory, there 

 seemed to be considerable evidence in its favour, 

 and there were no known objections, at least of any 

 great weight, against it. The case is very different 

 now. Erman's theory, as he presented it, is absolutely 

 untenable by anyone acquainted with what has been 

 learned respecting the August and November meteor 

 systems since 1866. 



The theory requires that the August and November 

 meteor systems should pass between the earth's orbit 

 and the sun, where they cross the plane of that orbit 



