ASTRONOMY. 175 



leugtli, corrected for tlio i)li()toy;rai)bi( ia,vs, wore suhniitted to the 

 meeting. Each plate contains a part of the sky extending 2° iu U. A. 

 by 3° iu Dec, and contains about 1,500 stars from the Gth to the 12th 

 magnitude, i. e., to the limit of visibility of an instrument of the size 

 used. The results have induced MM. Uenry to undertake the construc- 

 tion of a powerful instrument for this class of work, and they are now 

 engaged in constructing an object-glass of 0"'.34: diameter, which will be 

 corrected for the photographic rays and so constructed as to cover 

 clearly and without distortion the greatest possible space. In reference 

 to the advantages of this method of charting, Admiral Mouchez i^oints 

 out that work which ordinarily takes several months to i)erform can be 

 done in a single hour. It is considered that with the new apparatus 

 stars to the 13th or even 14th magnitude will probably be secured. 

 {The Observatory, October, 1884.) 



Photographic maps of stars. — A catalogue of the magnitudes of 500 stars 

 situated in the constellations Auriga, Gemini, and Leo Minor, has been 

 determined by the Eev. T. E. Espin from photographs taken with the 

 equatorial stellar camera at the observatory of the Liverpool Astronom- 

 ical Society. The magnitudes are compared with those given in Arge- 

 lander's Durchmnsterung, with which, in the large majority of cases, 

 they agree remarkably well. "There can be no doubt," says Mr. Espin 

 (in the Observatory for September), "that the photographic impression 

 is nearly equal to the eye magnitude in the case of two-thirds of the 

 stars. The other third fall into one of two classes : the bluish stars in- 

 crease in magnitude, while the reddish ones decrease." No positive 

 evidence of fluctuations of stellar light has been obtained ; in fact, of 

 the 500 stars whose magnitudes have been reduced from the plates, 

 only two cases of possible variation have been detected. Attempts 

 have also been made to photograph various star clusters and nebulae. 

 The results are very promising, but much improvement is to be looked 

 for in the practical working and reduction of the plates. {Athenceum.) 



COMETS, METEORS, ZODIACAL LIGHT, ETC. 



Statistics of cometic orbits. — Dr. Paul Lehmann, of Berlin, has reprinted 

 a compilation with the above title, which contains much interesting in- 

 formation in a tabular form. Two hundred and ninety-four cometic 

 orbits are more or less well known. Of these 221 have parabolic orbits, 

 and of the elliptic orbits 



7 have a period from 10,000 to 50,000 years ; 

 23 have a period from 1,000 to 10,000 years; 

 6 have a period from 500 to 1,000 years ; 

 9 have a pei'iod from 100 to 500 years ; 

 6 have a i^eriod from 50 to 100. years ; 

 5 have a period from 10 to 50 years ; 

 17 have a period from — to 10 years. 

 All the comets whose periods are undci- 10 years have direct motion, 



