60 



KNOWLEDGE 



[Mabch 1, 1898. 



Besides, the part of the Milky Way in Cygnus is remark- 

 able from more than one point of view. The luminous spot 

 p— y Cygui is the ciili/ luminous patch situated in the 

 " secondary branch,'' but near the dark space. It is an 

 exception to the manner of distribution of brightness over 

 the breadth of the Milky Way, between the Eagle and 

 Cassiopeia. It is evidently connected with several other 

 very brilliant regions (the spots a. — A, p— tt Cygni, etc., i 

 perhaps to the series of spots west of Altair). There are - 

 in the Milky Way other more luminous spots, but they I 

 are much smaller. Sir William Herschel here found his ' 

 maximum gauge (5<S8 stars in a telescopic field of 15'-4). 

 Not far from here, Kapteyn placed the centre of the 

 agglomeration of bright stars in the neighbourhood of the 

 sun. ^\ ithout wishing to dogmatize, it is here that I 

 would place the central condensation of a galactic spiral ; 

 the sun is thus found between this central nucleus and the 

 spirals directed towards Monoceros, in a region relatively 

 sparse . As to giving a rather more definite form to such 

 a spiral, it is a research that I have sometimes attempted, 

 Dut it would be premature to give the result here ; more- 

 over, many kinds of spirals are in accord with the theory. 



For want of space many considerations could not be 

 presented or only glanced at. In concluding, I wish to 

 insist that this theory does not pretend to give an explana- 

 tion of all the facts that are grouped about a phenomenon 

 so complicated as the Milky ^Vay, but that it is to be taken 

 above all as a " working hypothesis." 



Errata. — In my article in the .lanuary Number, 1898, 

 of Knowledge, p. 12, line 21, read : " Sir John Herschel 

 has not stated," etc. ; p. 13, line 15, read : " these points 

 have not been raised," etc. 



It would be just to add that the admirable photographs 

 of the Milky Way by Pickering have appeared after my 

 first article was written. 



^tttttU. 



[The Editors do not hold themselTes responsible for the opinions or 

 statements of correspondents.] 



TAKIABLE STARS. 

 To the Editors of Knowledge. 



Sias, — Since my note of .July 28th, Knowledge, October, 

 1897, I have seventy-five observations of R Scuti, making 

 in all one hundred and forty-eight up to the close of the 

 season, when the star passed westwards. Each of these 

 observations is the mean of two to five views. 



As heretofore stated, neither Chandler or "The Com- 

 panion " gave data for this star in 1897, but, following their 

 computations of previous years, the computed and observed 

 dates of the extreme phases of the star are as follows ; — 



From July 31st to September 21st the fall (excepting 

 some small fluctuations) was steady, and was followed by 

 a rise of similar character until November 0th, when it 

 began to fall again, making probably another reversal like 

 those of May 6th and September 21st. The latest obser- 

 vation of the star was November 17th. 



From 1890, December 29th — the computed date of 

 maximum of R Ijeonis that year, as given by " The Com- 

 panion — another maximum was due in 1897, November 7th ; 

 but the same authority, and Chandler, give the date as 

 October Hth, which is apparently a correction of thirty 

 days : but the star, on its last rise, appeared so near 

 daybreak that observations were inconvenient. It fell in 

 with my habits, however, and as soon as it rose above the 

 horizon before day, I gave it attention, and submit the 

 following data, which covers the means of twenty obser- 

 vations, but only the changes are given : — 



Milgr. Mair. 



1897. October 4 67 1897. November 3 7 1 



6 e-4 ., 4 7-2 



,. 12 6 3 „ C, 7-3 



13 6a .. 11 7-4 



17 61 „ 15 7-5 



21 60 .. 23 76 



2J. 6 3 „ 29 80 



26 6-6 December 6 8-3 



.30 6-9 



A maximum on October 20th is indicated, but some 

 other observers may be able to show that one occurred 

 earlier. It is to be hoped that someone has seen the star 

 in September. 



Ceti (Mirai has been at a stand for some days, nearly 

 on a level with 60 and 70, or at 5-5 magnitude. 



1 found S S Cygni at a maximum January 17th, at 

 8'5 magnitude, unchanged on 22nd, and a step or two 

 fainter on 25th. On 26th, the seeing being very poor, the 

 star was hardly visible. The period on this appearance 

 was forty-three days, the previous one being sixty days, 

 and it seems to have remained at maximom longer this 

 time than heretofore. 



Cloudiness has been the rule throughout the States at 

 nights for some time ; the mornings are more favourable, 

 but are hazy and damp ^^^_^^ Flanery. 



Memphis, Tenn., L js.A., 



28th January, 1898. 



* Kapteyn, Verslaijen Koii. Akadcmie i\ WeU iscli. te Amstji-dam 

 1892, 1893. 



THE DRAPER CATALOaUE. 

 To the Editors of Knowledge. 



Sirs, — Mr. Maunder has made a mistake in his article 

 in your February Number in describing the Draper Cata- 

 logue as a complete catalogue of the spectra of stars 

 down to the eighth magnitude. This is certainly incorrect. 

 But one drawback to this catalogue (as well as to many 

 other catalogues) is that we do not know the point down 

 to which it is complete, and are, consequently, liable to 

 err in applying its results to star distribution generally. 

 The Draper Catalogue is not complete up to the fifth magni- 

 tude. For instance, it does not contain the star 3 Aquarii, 

 measured 4-62 in the llanard Phutometri/, and 4-84 at 

 Oxford. Between the fifth and sixth magnitudes the 

 omissions are pretty numerous ; for example, 36 Aquilse, 

 measured 5-23 in both the Oxford and Harvard Catalogues. 

 The Harrard Ph^toiiietn/ contains some stars lying farther 

 south than any in the Draper Catalogue, but the latter 

 does not contain thirty or forty of those measured at 

 Oxford as under the sixth magnitude. 50 Pegasi is another 

 instance in which the omitted star is brighter than the 

 fifth magnitude. I am not writing for the purpose of 



