will include stars of the fourteenth magnitude. Many years must of 

 course elapse before the completion of the chart. When photography 

 was as yet in its infancy, a brilliant future, in connection with 

 astronomy, was prophesied for it by Arago, wlio wrote with 

 enthusiasm of a photographic picture he had seen of the moon. 

 Since then, lunar photography has developed to such an extent, 

 that, according to an American geographer " there are many parts 

 of the new world less accurately chartered than the " seas " valleys, 

 and mountains of the pale inconstant planet." Photography has 

 played a no less important part in revealing to us the nature of the 

 sun himself, the corona and the fiery streamers ; indeed, it is now 

 some years since Sir John Herschell wrote tha% "the orb of day 

 has been compelled to write its own history." 



An important fact disclosed by the spectroscope is, that 

 " terrestrial matter is not peculiar to the solar system above, but 

 is common to all the stars visible to us." Take, for instance, the 

 star Capella, whose spectrum is almo=t identical with that of the 

 sun, and whose constitution and temperature we have therefore 

 every reason to suppose is also the same. Professor Eowland has 

 shown that the lines of at least thirfcy-six terrestrial elements are 

 present in the solar spectrum ; as to fifteen other elements, there 

 is very little evidence that they are absent from the sun, but ten 

 others of which oxygen is one, have not yet been compared with 

 the sun's spectrum. Hence we may conclude that if the earth 

 were heated to the temperature of the sun, its spectrum would be 

 very similar. Professor Rowland is now endeavouring to discover 

 by means of these lines in the solar spectrum, which are as yet 

 unaccounted for, new terres trial elements which may possibly lurk 

 in rare earths and minerals, his method being to compare their 

 spectra with that of the sun. It is a curious fact that our know- 

 ledge of the spectrum of hydrogen came to us from the spectra of 

 the stars, and, in the same way, chemistry is even now seeking for 

 new elements in our earth by means of the solar sp ctrum. 



I may here mention in passing that, Professor Higgins entirely 

 confirms Professor Schuster's theory of the origin of the sun's 

 corona ; namely, that it consists of matter, flowing from the sun 

 under the influence of some force, probably electricity. Some 

 particles of the corona may possibly return to the sun, but the 

 greater portion, forming the long " fiery streamers," or rays of light 

 do not appear to return ; they may, not improbably furnish the 

 material for the Zodiacal Light, of which no other explanation has 

 as yet been offered. 



The spectra of the stars, although greatly diversified, may yet, 

 to a certain extent, be classified in groups, the sun's place being 

 apparently in about the middle of the series. Astronomers differ 



