1 62 LIGHT SCIENCE FOR LEISURE HOURS. 



We refrain, however, from speaking further on a 

 point respecting which we have no means of reasoning 

 satisfactorily. Mere guess-work is an altogether 

 unprofitable resource in the discussion of scientific 

 matters. 



Now that we have so powerful an instrument of re- 

 search as the spectroscope, there really seems hope 

 that even the hitherto inscrutable mysteries presented 

 by comets' tails may one day be interpreted. Each 

 comet which has been subjected to spectroscopic 

 analysis has revealed something new. Observations, 

 such as those which have been made on Brorsen's comet, 

 and on the two telescopic comets previously examined 

 by Dr. Huggins, are not merely valuable in themselves, 

 but as affording promise of what may be achieved when 

 some brilliant comet shall be subjected to spectroscopic 

 analysis. When we consider that all the comets yet 

 examined have been absolutely invisible to the naked 

 eye on the darkest night, whereas several of the great 

 comets have blazed forth as the most conspicuous 

 objects in the heavens, and have even been visible in 

 the full splendour of the midday sun, we see good 

 reason for the hope that far fuller information will be 

 gained respecting the structure of comets so soon as 

 one of the more important members of the family shall 

 have paid us a visit. 



Whenever such an event may happen it is not likely to 

 find our spectroscopists unprepared. It is probable that, 

 before long, every important observatory will be sup- 

 plied with spectroscopes. Already some of the most 



