Jamarv, 191 : 



KNOWLEDGE. 



19 



chart and the following elements obtained: — 



Semi- major Axis ... 

 Pesition Anf^le 

 Kccentricity 

 Inclination ... 



2° 35' 



.n. 



The pole of the Nubecula points almost exactly at 

 <) Doradus, and there is apparently a condensation 

 of nebulous objects at the poles. In the Nubecular 

 Minor only one \'-type star has been found, but the 

 general ap[)earance suggests a similar construction 

 to the Nubecular Major, with a position angle of 

 about 40". It is obvious that the mixing up of 

 Galactic and non-Galactic objects must take place 

 as observed by Herschel if the poles of these spheres 

 are inclined to the line of sight. For instance, a 

 \'-t\"pe star and a "white" nebula may be in 

 the same field, the \'-type star being on the 

 equator, while the white nebula is on the opposite 

 side of the sphere, and consequently situated at a 

 distance from the equator. 



Having examined this Uiii\irsc in miniature we 

 mav now go on to apply its lessons to the Milky 

 Wav. We take a sheet of paper and divide it into 

 squares, and along the top write the hours of Right 

 Ascension, and down the sides the Declinations. 

 Next we lay down the path of the Milky W'ay 

 according to Gould: then having made a collection 

 of all the known Galactic objects, viz. — Type \' 

 stars, gaseous nebulae, Orion stars with bright hues, 

 temporary stars, we insert them in their proper 

 places. Immediately it is obvious that the V type 

 stars tend to collect in groups, the two largest groups 

 are in proximitv to >; Argus and 1' Cygni, both of 

 which stars have bright lines and have undergone 

 remarkable fluctuations in light. >; Argus is associated 

 with a remarkable nebula, and Professor Max ^^'olf 

 finds vast nebulous patches in the C'ygnus region. 

 Further, these places approximately coincide with 

 each end of the great bifurcation of the Milky Way. 

 A glance at our chart shows us also that the 

 \'-type stars are much more plentiful in the 

 region between Argo and Cygnus than elsewhere, 

 and further that they tend to follow the medial 

 line, and are grouped upon it at intervals. The 

 gaseous planetary nebulae follow the same law, save 

 that they are more widely distributed, and prefer 

 the following rather tiian the preceding of the two 

 Galactic streams. The distribution of the Orion 

 stars with bright lines points to the same fact 

 though in a less marked manner, while the temporan,- 

 stars are more evenly distributed. Taking the per- 

 centages of each of these groups we obtain the 

 following table : — 



Type Plan. Orion Temporary 



Milkv Wav. V. Neb, Stars. Stars. 



Medial circle 78-S ... 5-4 ... 15-8 ... 25-0 



Preceding stream ... ... 26-8 ... 28-9 ... 40-0 



Following stream ... 21-2 ... 67-8 ... 55-3 ... 35-0 



If we examine the region from Argo to Cygnus we 

 find in each case the tendency is rather to groups 

 than to uniform distribution. Passing from the 

 great Argo group at Galactic longitude of 255° a 

 group of V-type stars occurs at longitude 275", a 

 second at 320". At this spot the planetary nebulae, 

 so far scarce, begin to collect on the following 

 stream of the Gala.xy, coming to a maximum at 

 longitude 340", and here in turn begin the more 

 scattered temporary stars extending up to longitude 

 360'^. The planetary nebulae still continue plentiful 

 up to longitude 30", then there is apparently a gap 

 till the P Cygni region is reached. Beyond this the 

 Galaxy is singularh- poor in bright line objects, and 

 the stars of t\pe V, so far as they are at present 

 detected, disappear altogether between longitude 

 110" and 190°. Before the latter degree is reached 

 the Orion stars with bright lines begin to appear, and 

 soon become numerous, lying persistently South of 

 Milkv Way central line. One group seems con- 

 nected remotely with the Orion nebula, and a 

 second is found amongst the bright stars which 

 mark the Southern limit of Canis Major. The 

 following table shows in a striking manner the 

 difference between the Argo-Cygnus region and the 

 remaining 213 degrees of Galactic longitude : — 

 Percent.^ges. 



Type Temporary Plan. Orion 



Des(rees. V. Stars. Neb. Stars. 



Argo-Cygniis ... 40-8 ... 81-7 ... 70-8 ... 66-7 ... 55-9 



Rest of Galaxy ... 59-2 ... 18-3 ... 29-2 ... ii-i ... 44-1 



Whatever inference we may draw from these 

 results must be carefully guarded with the proviso 

 that it is correct only as far c7.s our kiioicledf^e at 

 present extends. Some thirty years ago the \"-type 

 stars were confined to the Cygnus group ; to-day the 

 vast majority are found to extend between >; Argus 

 and P Cygni ; but at any rate we seem warranted in 

 drawing the conclusion that in the case of the brighter 

 members in each group of Galactic objects, the ratios 

 of distribution are fairlv complete. With increased 

 telescopic power the gaps ma\' be filled up ; but it 

 will be with objects fainter than those at present 

 known, and one or two alternations will present 

 themselves, either the causes which produce \'-t\pe 

 stars, and so on, are less active in one direction than 

 another, or we are decidedly nearer one section of 

 the Galaxy than we are to the other. At present the 

 general consensus of opinion seems to be in favour of 

 the latter alternative. 



Our illustrations show in the large plate the Milky Way from ten degrees to fifty degrees south of the Ecjuator. and 

 the four smaller ones (taken b\- Professor Wolf with a small lens, and reproduced by his courtesy), carry us north as 

 far as Perseus. Thus they cover the whole of the bifurcation, which, it will be seen, is much more obvious to the 

 naked eye than on the pholographic plate. Throughout there will be noticed semicircular dark spaces, probably of 

 absorption matter. 



