A. MATHEMATICS AND ASTRONOMY. 37 



interested in these studies will be glad to learn that Mr. 

 Proctor has now concluded to publish his chart in the shape 

 of a photograph, eighteen inches in diameter ; and by means 

 of which, with the naked eye, one may obtain a highly in- 

 teresting and correct view of the appearance of the heavens 

 as seen with a small telescoj^e. 



SUCCESS OF THE SYSTEM OF CABLE COMMUNICATION OF 



CELESTIAL PHENOMENA. 



The arrangement made by Professor Henry, of the Smith- 

 sonian Institution, a few months ago, for the interchange be- 

 tween America and Europe, by Atlantic cable, of important 

 astronomical discoveries and announcements, appears to have 

 borne excellent fruit. One great object of this movement 

 was to enable astronomers in all parts of the world to con- 

 centrate attention upon any celestial phenomenon before too 

 great a change of place had occurred, or before the interven- 

 tion of a long period of moonlight after the first discovery. 

 On the 26th of May last Professor Henry announced a new 

 planet, discovered by Professor Peters, to the Observatory 

 of Paris, among other institutions, and on the following night 

 it was looked for by the director of the Observatory of 

 Marseilles, who at once detected it, and subjected it to a 

 careful criticism. The announcement of three planets has 

 thus far been made from the Smithsonian Institution to 

 Europe ; the only return communication being that of a 

 telescopic comet, discovered at Vienna on the 5th of July. 

 On being notified of the fact. Professor Hough, of the Dudley 

 Observatory, at Albany, made search for it, and succeeded 

 in finding the object without any difiiculty. 



THE DIAMETER OF THE FIXED STAES. 



Stephan, of Marseilles, proposes the following method of 

 determining the apparent diameter of the stars. If, through 

 an excellent telescope, a star, whose angular diameter is real- 

 ly nothing, be viewed with a sufficiently high magnifying 

 power, the image is seen to be a bright spot surrounded 

 by the concentric rings of light and shade which are called 

 diff'raction rings. Fizeau has shown that these rings, if of 

 extreme faintness and distance from the central spot, can 

 only be formed when the angular diameter of the source of 



