April, 1892. 



OUR COLUMNS. 



73 



give the positions of the brighter members of this mighty host with more or less 

 exactness. Perhaps the most remarkable is the Durchmusterung of Argelander, which 

 includes over 300,000 stars in the northern hemisphere. Up to a comparatively recent 

 period, all the fixed stars, with a very few exceptions, were regarded as invariable in 

 brightness, and there can be no doubt that, so far as a vast majority of them is 

 concerned, this is the case. But scarcely a year passes without additions being made 

 to the catalogue of variable stars, and there are good grounds for the belief that as 

 observers increase and closer attention is paid to the subject the number will be still 

 further augmented. In this department of Observational Astronomy, the opera -glass 

 and lunette have done, and continue to do, good service, owing to their portability, 

 the wide field of view they display, and to the ease with which they can be used 

 in situations where a larger instrument would be out of the question. Hence anyone, 

 who, having entered on the brief apprenticeship to Urania just described, still retains 

 enough enthusiasm to wish to discover some of the secrets she reveals to her 

 votaries, cannot do better than follow up the subject of variable stars, and add his 

 name to the lengthening roll of amateur observers who are devoting themselves to 

 this fascinating branch of research in all quarters of the world. 



Variable stars are divided into distinct classes, which may be thus distinguished — 

 (1st) Stars Avhich for a shorter or longer period remain faint objects, and then suddenly 

 increase in magnitude for a time, attain a maximum, and as rapidly revert to their 

 first condition. This they do periodically, — the period varying in length from six 

 months to two years. (2nd) Variables which exhibit two or more maxima and 

 minima during the period of change. (3rd) Stars which for a time appear to be 

 of constant brightness, but suddenly (often in the course of a few hours) become 

 apparently obscured for a brief period and then as suddenly regain their former 

 magnitude. Besides these types, there are well marked instances of steady continuous 

 change, which has probably been going on for ages ; of sudden changes, apparently 

 governed by no known law ; and lastly, of those more or less startling phenomena, of 

 which we had an example in the constellation Auriga so recently as last January, — 

 Temporary Stars. It may be noted, by the way, for the encouragement of opera-glass 

 observers, that this ' Nova ' in Auriga was discovered at Edinburgh by an amateur, 

 Mr. Anderson, with a small pocket telescope, and that another, U. Orionis, of an 

 equally remarkable type, was detected by Mr. Gore with a binocular in December, 

 1885. Nor must it be forgotten, as showing what may be accomplished with very 

 humble optical assistance, that many of the minor planets between Mars and 

 Jupiter were discovered by M. Goldschmidt, using a lorgriette, from the balcony of his 

 house in the Faubourg St. Germain. 



f To he continued.) 



Nothing gives the Book Committee greater official pleasure than the sight of a long 

 list of volumes suggested by members of the Library in the Proposal Book or Cards. 

 But why is it that, when the standing orders have not been complied with, and the 

 Committee have often regretfully added the note "no price!" — why is it that the 

 proposer fails, as a rule, to take any further interest in the matter ? Do our members, 

 many of whom must be well-read political economists, affect to consider that " no 

 price" is to be taken to mean "no value?" The proper course would be to suggest 

 the book again with the information supplied. 



