THE FUTURE OF ASTRONOMY 107 



the man behind the gun. The case is not unlike that of a battleship. 

 Would a ship a thousand feet long always sink one of five hundred feet ? 

 It seems as if we had nearly reached the limit of size of telescopes, and 

 as if we must hope for the next improvement in some other direction. 



The second great advance in astronomy originated in America, and 

 was in an entirely different direction, the application of photography 

 to the study of the stars. The first photographic image of a star was 

 obtained in 1850, by George P. Bond, with the assistance of Mr. J. A. 

 Whipple, at the Harvard College Observatory. A daguerreotype plate 

 was placed at the focus of the 15-inch equatorial, at that time one of 

 the two largest refracting telescopes in the world. An image of a Lyrse 

 was thus obtained, and for this Mr. Bond received a gold medal at the 

 first international exhibition, that at the Crystal Palace, in London, in 

 1851. In 1857, Mr. Bond, then Professor Bond, director of the Har- 

 vard Observatory, again took up the matter with collodion wet plates, 

 and in three masterly papers showed the advantages of photography in 

 many ways. The lack of sensitiveness of the wet plate was perhaps the 

 only reason why its use progressed but slowly. Quarter of a century 

 later, with the introduction of the dry plate and the gelatine film, a 

 new start was made. These photographic plates were very sensitive, 

 were easily handled, and indefinitely long exposures could be made with 

 them. As a result, photography has superseded visual observations, in 

 many departments of astronomy, and is now carrying them far beyond 

 the limits that would have been deemed possible a few years ago. 



The third great advance in astronomy is in photographing the- 

 spectra of the stars. The first photograph showing the lines in a stellar 

 spectrum was obtained by Dr. Henry Draper, of New York, in 1872. 

 Sir William Huggins in 1863 had obtained an image of the spectrum 

 of Sirius, on a photographic plate, but no lines were visible in it. In 

 1876 he again took up the subject, and, by an early publication, preceded 

 Dr. Draper. When we consider the attention the photography of stellar 

 spectra is receiving at the present time, in nearly all the great observa- 

 tories in the world, it may well be regarded as the third great advance 

 in astronomy. 



What will be the fourth advance, and how will it be brought about ? 

 To answer this question we must consider the various ways in which 

 astronomy, and for that matter any other science, may be advanced. 



First, by educating astronomers. There are many observatories 

 where excellent instruction in astronomy is given, either to the general 

 student or to one who wishes to make it his profession. At almost any 

 active observatory a student would be received as a volunteer assistant. 

 Unfortunately, few young men can afford to accept an unpaid position, 

 and the establishment of a number of fellowships each offering a small 

 salary sufficient to support the student would enable him to acquire the 



