154 LIGHT SCIENCE FOR LEISURE HOURS. 



weighty. If meteor streams lying between the earth 

 and the sun diminished our supply of heat, we should 

 expect that some among them would be visible upon 

 the sun's face at those times, when duly magnified by 

 powerful telescopes. A distant flight might, indeed, 

 escape without any of its individual members being 

 detected. But even then one would expect a measur- 

 able decrease of the sun's brightness, and hitherto 

 nothing of this sort has been recorded by scientific 

 observers. 



But after all, as I pointed out in the paper above 

 referred to (Knowledge, for May 26, 1882), the terres- 

 trial test of Erman's theory is the best. If meteoric 

 bodies come between the earth and sun at any time, in 

 such numbers as to make us feel cold in their shadow, 

 they must cool the whole earth, not England, or Europe, 

 or the northern hemisphere. * If, then,' I wrote at that 

 time, ' in a careful comparison of the mean daily 

 temperature at observatories all over the earth, it is 

 found that the cold snaps of February, April, and May 

 are everywhere to be recognised, then it must be at 

 least admitted that the cause of the peculiarity is to be 

 sought outside the earth herself.' 



This, which seemed to me unlikely when I wrote 

 those lines, has now happened. There seems no 

 reason to doubt that the relatively cool weather of 

 February in the southern hemisphere (I say relatively 

 because, of course, February belongs to the warmest 

 part of the southern year, corresponding to our August) 

 is not coincident by a mere accident with the cold 



