18 LIGUT SCIENCE FOR LEISURE HOURS. 



a tyro in the use of the spectroscope, doubts might very 

 reasonably have been entertained respecting the ex- 

 actness of the observations on which the discovery 

 rests. 



It was suggested many years ago, long indeed be- 

 fore the true powers of spectroscopic analysis had been 

 revealed, that perhaps if the light of the aurora were 

 analyzed by the prism, evidence could be obtained of 

 its electric nature. The eminent meteorologist Dove 

 remarked, for instance, that " the peculiarities pre- 

 sented by the electric light are so marked that it ap- 

 pears easy to decide definitely by prismatic analysis, 

 whether the light of the aurora is or is not electric." 

 Singularly enough, however, the first proof that the 

 auroral light is of an electric nature was derived from 

 a very different mode of inquiry. Dr. Robinson, of 

 Armagh, discovered in 1858 (a year before KirchhofFs 

 recognition of the powers of spectroscopic analysis) 

 that the light of the aurora possesses in a peculiar de- 

 gree a property termed fluorescence, which is a recog- 

 nized and characteristic property of the light produced 

 by electrical discharges. " These effects," he remarks 

 of the appearances presented by the auroral light under 

 the tests he applied, " were so strong in relation to the 

 actual intensity of the light, that they appear to afford 

 an additional evidence of the electric origin of the phe- 

 nomenon." 



Passing over this ingenious application of one of 



