24 



KNOWLEDGE. 



Jantarv, 1911. 



at the present day and the attention shown to them. .A mere 

 . glance at a catalogne of such objects will make this perfectly 

 clear and illustrate how many, and e\en essential facts, remain 

 unknown : especially as to long period variables, which should all 

 be followed in a permanent manner in \iew of a better know- 

 ledge of their light- curves. 



In order to bring this out more clearly, I ha\'e drawn up 

 a table of the disco\ery of ^•ariable stars during recent years. 

 For this, I deduced from a manuscript catalogue of such 

 objects, for each year during the last decade (1900-19091. the 

 mmiber of variables announced as being variable, and to 

 which a ■■ provisional number " has been affixed, together with 

 the number of the same stars that have received up to the 

 present a " final name " — a combination of two letters — as 

 explained hereafter, and the proportion between these two 

 series of figures. 



Variables in clusters have not been included in the lists. 

 but novae or temporary stars have been, since thev are in 

 the A.G. lists they were considered as lettered. The 

 discovery at Harvard and at Heidelberg of a large number 

 of very faint \ariables accounts for such great totals as 

 that of 1904, for example, and I intended at first to exclude 

 them from the statistics; but, as the variability of several of 

 these objects has been confirmed and as they thus received 

 final names, I ultimately included them. 



In dealing with the total number of " pro\isional \ariables ' 

 care must be taken to exclude some " apparent " variables. 

 For instance 19.1900 Puppis is a rediscovery of / Puppis : 

 67.1901 and 74.1901 are /) Cassiopeiae and k Persei respectivelv. 

 and as they possess Bayer (Greek) letters, they will never 

 receive final names in the usual nomenclature, and have been 

 excluded: 2.1902 is a rediscovery of U Lacertae : 9.1902 and 

 43.1909 are the result of mistakes and never had a real 

 existence. 



In the following table, the first column contains the total 

 (apparent) number of provisional numbers of variables as 

 shown by the Astroiiomischc Xachriclitcn: the second the 

 true or real number of discoveries; the third, the number of 

 variables which have been lettered up to the present (including 

 the latest list of the A.G. Committee in A.X. 4364); the 

 fourth, the number of variables still inilettered and of which, 

 therefore, little or nothing is known ; the fifth and final 

 column, the proportion between the real number of discoveries 

 and the lettered \ariables. The small number of lettered 

 variables in 1909 is of course partly due to the fact that they 

 had only been known a short time. 



conducted by .Mr. C. L. Brook. F.R..A.S., an amateur himself, 

 a splendid and almost unique opportunity to achieve, with the 

 most simple appli.iiices, a mass of useful work, and to contribute 



It will be seen that in recent years the proportion between 

 new variables and those that are more or less " settled " is a 

 little more than 20%, and that 66% of all the variable stars 

 discovered during the last decade still awaits confirmation. 

 This fact will appear more .strikingly still on the inspection of 

 Figure 1. where they ha\e been graphically represented. 



If British amateurs will consider that their own countrv 

 offers them, through the medium of the "Variable Star 

 Section " of the " British Astronomical Association," so ablv 



Figure 1. 

 The Discovery of \'ariable Stars. 



The tliin line represents the number of vari.-ible slurs discovered each year since 



1900 ; the interrupted line the number of the same stars whose variability has been 



confirmed ; and the hea\-y line at the base, the proportion between both. 



