28 ANNIVERSARY ADDRESS. 



apparatus and the quickest sensitive plates, and they reveal and 

 record the existence of thousands of stars which have never before 

 been recorded, and very many too faint to have been seen with 

 any telescope, and likewise give the first photographic delineation 

 of the remarkable nebula that surrounds the star Eta Argus ; they 

 show strange details in its convolutions which seem to prove 

 beyond question, that it is a great spiral structure, and they con- 

 firm the discovery made by Mr. Russell twenty years since, that 

 one of the most brilliant and remarkable parts of the nebula as 

 seen by Herschel, has totally disappeared. In the great coal sack 

 or dark space in Crux these photographs reveal a multitude of 

 stars, and in fact show that over nearly all of it, stars are about 

 as numerous as in the neighbouring parts which look so bright to 

 the unassisted eye ; only one small space is devoid of stars, and 

 at the same time they shew a number of dark spaces, lanes as it 

 were in the Milky- Way, and other striking peculiarities never 

 before suspected. The modern use of dry sensitive plates has put 

 into the hands of astronomers a new means of research which 

 makes it possible to advance in several directions entirely new, 

 and in others to push discovery far beyond the point possible with 

 the most powerful telescopes ; heretofore it has been impossible 

 to see large sections of the sky at one view and highly magnified, 

 but the photograph does both and forms a permanent record of 

 star groups amongst the countless multitudes of the Milky-Way 

 that have never before been seen. In fact the photograph is 

 equivalent to seeing the Milky- Way with new, or more correctly 

 speaking, differently constituted eyes ; the camera virtually sees 

 the stars by the chemical energy of their light and the result is a 

 survey of the stars from a new standpoint and brings with it 

 many advantages. 



Since the world's astronomers met in Paris to arrange for the 

 grand photographic survey of the whole heavens, by which every 

 star down to the fourteenth magnitude is to be brought from its 

 hiding place and included in the permanent records of astronomy, 

 just four years have elapsed, which have been spent in preparations 



