The Astrophysical Observatory 4 21 



while in place of the equatorial and of the meridian instru- 

 ments which are elsewhere used in the same way, night after 

 night during perhaps a large part of the lifetime of the ob- 

 server, the apparatus of the new astronomy is frequently 

 modified, and, in an active observatory for solar research, will 

 probably be found to be undergoing repeated change, the 

 work being more or less of the nature of discovery, and each 

 discovery leading probably to some alteration and improve- 

 ment of the means by which the last was attained. 



In the half century which has elapsed from the time when 

 President Adams manifested so strong an interest in astron- 

 omy, and after the government had erected and provided for 

 an observatory, the United States Naval Observatory, at 

 the capital, necessarily devoted to the pursuit of the old 

 astronomy, since at that time there was none other, the 

 conception of another form of astronomy arose in the minds 

 of men of science ; and in 1861, when Kirchhoff and Bunsen 

 published their researches on spectrum analysis, the " new 

 astronomy" may be said to have been born. 



It has been modified since in many directions, and as its 

 public importance became recognized, it has at the hands of 

 various European governments had special establishments 

 consecrated to it. Thus, in France, in the Observatory of 

 Meudon, near Paris, constant observations have been carried 

 on upon the solar surface by Monsieur J. Janssen, by means 

 of photographic processes, which have greatly surpassed in 

 accuracy any preceding ones, while parallel researches have 

 gone on there upon the nature of the absorption which pro- 

 duces the various lines of the spectrum, and other matters of 

 interest in connection with solar studies. 



The French government for two hundred years has had 

 an observatory, within the city of Paris, devoted to the 

 classical astronomy; and this new installation, at the Pare 



