182 



KNOWLEDGE. 



[August 1, 1895. 



plication of the Galactic image in nearly all its parts, 

 renders it difficult for us to believe that in all these cases 



FlO. 5. — Eeduetion of part of the Bonu Atlas, in AquUa. (Argelandor.) 



we have only penetrated into irregular masses, accidentally 

 brought rather near to us, but which do not belong to a 

 zone of great extent. 



In short, if the results given in the preceding paper are 

 considered, the conclusion most forcibly presented to us 

 is, that it becomes extremely probable that the great 

 majority of the fainter stars of the Milky Way — so far as 

 their existence is revealed to us by photography or direct 

 vision — are not much more distant from us than the stars of 

 the ninth and tenth magnitudes, at least in the regions to 

 which our researches have extended. The Galactic system, 

 or at any rate that portion which is accessible to our 

 means of observation, must thus have but little depth in 

 proportion to its diameter. 



The extension of the researches here given to the whole 

 of the Milky Way may throw more light upon these 

 problems. But at first it would be necessary to possess a 

 greater number of observations on the aspect of the Milky 

 Way with the naked eye.* 



CLUSTER M. 46, AND NEBULA W IV. 39 ARGUS. 

 K.A. 7h. 37m., Decl. S. 14 30'. 



THE photograph covers the region between E.A. 

 7h. 35m. 39s., and E.A. 7h. 38m. 54s. ; Decl., 

 between 14 0' and 15 14' South. 

 Scale, 1 millimetre to 23'61 seconds of arc. 

 Co-ordinates for the epoch a.d. 1900 of the 

 Fiducial stars marked with dots. 



Star (•)• D-M., No. 2082. 

 7h. 35m. 48-7a. Decl., S. 15^ 1-9'. 

 D.M., No. 2099. 

 Decl., S. 14° 49-9'. 

 D.M., No. 2158. 

 Decl., S. 14^ 7-2'. 

 D.M., No. 2171. 



Star ( •• ). 

 7h. 36m. 28-53. 



Star (•.•). 

 7h. 38m. 3'6s. 



Star ( : : ). 



Zone — 14 . 



Mag., 5-4. 



Zone— 14°. 



Mag., 8-7. 



Zone — 14". 



Mag., 8-6. 



Zone — 14°. 

 '. Mag., 8-8. 



E.A. 



E.A. 



R.A., 



E.A. 



7h. 38m. 20-3S. Decl., S. 14° 40-4' 



The photograph was taken with the 20-inch reflector on 

 February 24th, 1894, between sidereal time Gh. 2m. and 

 7h. 32m., with an exposure of the plate during ninety 

 minutes. 



Eefekences. 



The cluster is N. G.C. No. 2437, G. C. No. 1564, and 

 h 463. The nebula is N. G. C. No. 2438, G. C. No. 1565, 

 and h 4G4 = 8093. 



* Some astronomers, both professional and amateur, in Germany 

 and France have offered to assist me by sending me r^onie oltservations 

 of the Milky Way in order that I may collate them and publish a 

 summary of them later on. I should be very pleased if, among the 

 fellow-countrymen of Las.'ell, llartli, and Boeddicker, a large number 

 of persons were found who would wish to participate in a similar 

 systematic investigation of the Milky Way with the naked eye, and 

 wlio woidd send me their address in sign of their desire to co-operate 

 in the work. 



Sir .7. Herschel (G. C.) describes the cluster as a re- 

 markable object, very bright, very large, very rich, with a 

 planetary nebula involved, which he describes 

 as pretty bright, pretty small, extremely little 

 extended, barely resolvable ; 3'75s. in diameter. 

 Lord Eosse (P/iil. Tnms., 1850, p. 513, 

 PI. XXXVIII., Fig. 12; and Ohs. of AV/;. atul 

 CI. of St., p. Gl) records twenty-one obser- 

 valions of the nebula made between the years 

 1848 and 187G. He saw it first as a planetary 

 nebula GO'' in diameter, and subsequently as 

 an annular nebula with two stars and a 

 suspected third star in it. Much uncertainty 

 as to the character of the object is shown by 

 the records, and in the last observation (187G) 

 ' It can hardly be called a planetary nebula." 

 north preceding the centre is estimated as of 



he says, ' 



The star 



13th-14th magnitude, and the other star near the foUowinr/ 



edge 16th magnitude. 



Lassell (Mew. B.A.S., Vol. XXIII., p. 60, PI. II. Fig. 5) 

 describes it as a planetary nebula, and saw two stars in it. 



The photograph shows the nebula to be of the annular 

 type, and as perfect in outline as M 57 Lyras, and is seen 

 projected on a plane facing the eye, and circular in form. 

 The ring is most condensed on the north following side, 

 and there are three stars in the interior. The brightest of 

 them (13th-14th magnitude) is near the centre ; another, 

 of about 16th magnitude, is on the south preceding side; 

 and the third, which is below 16th magnitude, is almost 

 involved in the ring on the south following side. There is 

 also evidence of very faint nebulosity in the ring itself. 



The nebula is either involved or else in alignment with 

 the northern part of the cluster, which is a magnificent 

 aggregation of stars between the 9th and 16th magnitude, 

 and the photo-fields around it are crowded with stars 

 having the usual remarkable groupings and numerous 

 apparent double, triple, and multiple stars. 



Hcttcrs. 



[The Editor docs not hold himself responsible for the opinions or 

 statements of correspondents.] 



• 



FLtTCTUATIONS OF MIRA CETI. 

 To the Editor of Knowledoe. 



Sir, — The discussion on Mira Ceti can well wait further 

 evidence, which I feel confident will be forthcoming in 

 good time, but for your satisfaction I submit the following. 



According to " The Companion to the Observatory " for 

 1895 the maximum of Mira Ceti occurs on January 13th 

 this year : but on that day the star was only of the seventh 

 magnitude, fuUy five magnitudes less than the maximum 

 in light, and less than 66, 67 and 71 Ceti, with which I 

 compared it until it exceeded them in light, when I used 

 S and y in the same constellation. 



My record reads : — 



This, in my opinion, was the maximum light given by 

 Mira this season, and it lasted about ten days. 



I felt dissatisfied with the figures between January 13th 

 and February 9th and between February 9th and 24th, and 

 attributed their seeming inconsistency to my own person- 

 ality. As I was in doubt, however, and was unwilling to run 

 ill vain, I addressed an astronomer, whose name, did I feel 

 at liberty to publish it, would be sufficient support of my 



