324 the president's address. 



not only necessary to the astronomer, but is also one of great 

 attraction to all intelligent persons, viz., the relative magnitudes 

 of the stars. A mere tyro in astronomy cannot fail to notice the 

 very distinctive variations of brilliancy in different quarters of 

 the heavens, for instance, between the splendid and thickly 

 studded constellations of Orion, Ursa Major, or Taurus, and the 

 less favoured constellations of Hydra, Camelopardus, or Pisces. 

 But, apart from all popular notions of the appearance of the 

 starry heavens, it is of the highest scientific importance that the 

 relative brightness of all the principal stars should be correctly 

 ascertained. Until lately, the most trustworthy magnitudes have 

 been the eye-estimations of Prof. Argelander and Dr. Heis, both 

 of whom have made the subject a special study. Their separate 

 scales of magnitudes sensibly agree with each other, and they 

 have hitherto been adopted in all observatories. 



The eye-estimations of magnitude are, however, likely before 

 long to be superseded by a new series of determinations made 

 by a process combining new principles and apparatus in the 

 investigation. Prof. E. C. Pickering of the Harvard Observa- 

 tory, has devised a photometer, by which he has carefully 

 measured the relative intrinsic light of every star to the sixth 

 magnitude, visible in the northern hemisphere, to the number of 

 4,260 ; while Prof. Pritchard, of the University Observatory, 

 Oxford, by what is called a series of extinctions by a wedge 

 photometer, has likewise measured the relative luminosity of 

 2,784 stars. The results of the two astronomers, although 

 determined by photometers constructed on totally different 

 principles, agree very closely, and they indicate that a great step 

 has been accomplished towards a perfect knowledge of the rela- 

 tive lustre of the stars, from the brilliant dog-star Sirius to the 

 faintest gem of the sixth magnitude. 



And now, ladies and gentlemen, I have laid before you, in 

 as brief a manner as possible, a few astronomical conclusions, 

 some of which I trust will be remembered, although the subject 

 generally may be a little technical, and one not easily mastered 

 in a day. We have, in some measure, seen how the constitution 

 of the boundless universe has been partially unfolded by the 

 energy and perseverance of a small band of devoted men of 



