PHILOSOPHICAL SOCIETY OP WASHINGTON. -io 



The inference deducible, therefore, from this brief and hasty 

 survey is that no indication is afforded by Prof. Lovering's results, 

 of an extra-terrestrial matter playing any part in the auroral dis- 

 charge ; and that we must regard the phenomenon as a terrestrial 

 one, notwithstanding the reach of 400 and 500 miles, which has 

 been ascribed to the luminous beams. 



Following this communication, remarks were made as follows : — 



Mr. E. B. Elliott thought that the frequency of auroras had 

 a simple relation to the change in the length of the earth's radius 

 vector. Auroras occur most frequently when the earth is most 

 rapidly approaching to or receding from the sun — that is, at times 

 when the radius vector is most rapidly changing its length. To 

 illustrate this view Mr. Elliott presented a table comparing by 

 months the frequency of auroras, with the monthly differences in 

 the logarithms of the earth's radius vector. The monthly periods 

 of maximum frequency of auroras being in March and October, 

 while the periods of the most rapid increment and decrement of 

 the logarithm of the radius vector were likewise respectively in 

 the months of March and October. 



The data employed by Mr. Elliott to show the frequency of 

 auroras embraced from ten to twelve thousand observations, as 

 given in the general catalogue of auroras published by Professor 

 Lovering. 



Mr. C. Abbe stated that he had lately carefully studied the valu- 

 able tables of Prof. Lovering, and had, moreover, during the past 

 year, systematically collated all the observations of auroras ac- 

 cessible to him, with the tri-daily weather charts of the Array 

 Signal Office, and had arrived at a firm conviction that the aurora 

 stood in an intimate relation to the condition of the earth's atmo- 

 sphere ; that, in fact, although its ultimate cause might be ever 

 acting — might be cosmical, and might therefore be subject to 

 periods of one, eleven, and fifty-five years — yet on the other hand 

 that cause could not produce its visible effect, the aurora, except 

 in certain conditions of the earth's atmosphere, and that therefore 

 certain remarkable relations existed between auroral phenomena 

 and terrestrial atorms, &c., some of the details of which he then 

 briefly indicated. 



