214 LIGHT SCIENCE FOR LEISURE HOURS. 



velocity would suffice to carry it away for ever from 

 the sun's controlling influence. Much more, therefore, 

 would the outrush of such matter suffice to explain the 

 extension of the coronal streamers. 



It would require only very moderate assumptions 

 respecting the retarding influence of the solar atmo- 

 sphere, to prove that .the least of the jet prominences 

 must have required a velocity of ejection competent 

 to carry the vapours of metals as far as the outermost 

 observed limits of the radiated corona. 



COMETS. 



OF all the objects with which astronomers have to deal, 

 comets are the most mysterious. Their eccentric 

 paths, their marvellous dimensions, the strange changes 

 to which they are subject, have long been among the 

 most striking of the wonders of astronomy. There is 

 something specially awe-inspiring, too, in the thought 

 of the gloomy domains of space through which the 

 comet that visits our system for a brief time has for 

 countless ages been travelling. Ordinary modes of 

 measuring space and time fail us, indeed, in speaking 

 of these wonders, or at least convey no real meaning to 

 the mind. If the comet, for instance, which was in 

 1874 a conspicuous object in our northern skies be of 



