1 8 LIGHT SCIENCE FOR LEISURE HOURS. 



consider comets' tails as consisting of electric matter ; ' 

 adding that ( this would account for the undulations 

 and other appearances which have been noticed, as, 

 for instance, that extraordinary one seen by M. Chladni 

 in the comet of 1811, when certain undulatory ebulli- 

 tions rushed from the nucleus to the end of the tail, a 

 distance of more than ten millions of miles, in two or 

 three seconds of time.' To this we may add the some- 

 what bizarre theory suggested by Sir John Herschel, 

 that the matter forming the zodiacal light is ( loaded, 

 perhaps, with the actual materials of the tails of millions 

 of comets, which have been stripped of these append- 

 ages in the course of successive passages round the 

 immediate neighbourhood of the sun.' 



Now hitherto no comet with a sufficiently brilliant 

 tail for spectroscopic analysis has appeared since 

 Kirchhoff's invention of that mode of research. Al- 

 ready our physicists had been looking forward anxiously 

 for the appearance of such a comet as Donati's or 

 Halley's. But Angstrom's recent discovery, and the 

 evidence which seems to associate the tails of comets 

 with the auroral and zodiacal lights, renders our spec- 

 troscopists doubly anxious to submit a comet's tail to 

 spectroscopic analysis. It is far from being unlikely 

 that three long-vexed questions the nature of the 

 aurora, that of the zodiacal light, and that of comets' 

 tails will receive their solution simultaneously. 



I had scarcely completed the above pages when news 

 was brought from America that the spectrum of the 

 sun's corona, as seen during the recent total solar 



