202 Mr Hinks, Suggestions for a theory of the Milky Way 



There are not yet available determinations of proper motion 

 for stars fainter than 9| mag. Stars which have appreciable 

 proper motion are almost uniformly distributed over the sky, and 

 show little or no tendency to aggregation on the plane of the 

 Milky Way. These are, on the whole, the nearer stars. They may 

 perhaps be considered as forming a star cloud of which the Sun is 

 a member. 



The author would suggest that these facts of star distribution 

 are consistent with the hypothesis that the stars are distributed in 

 a series of more or less independent clouds roughly in one plane. 

 The cloud in which our Sun is situated would then supply the 

 stars of sensible proper motion which are uniformly distributed ; 

 the neighbouring clouds would supply the bulk of the stars down 

 to the eleventh magnitude, which are to a considerable extent 

 distributed about centres in the galactic plane ; the more distant 

 star clouds would make the Milky Way proper as seen by the 

 unaided eye. 



The smaller cloud of Magellan would on this hypothesis be one 

 of the distant star clouds that happened to lie far out of the 

 general plane. The greater cloud of Magellan may perhaps be 

 more properly considered a nebula and star cluster cloud than 

 a star cloud. 



The distribution of the nebulae (other than gaseous) may also 

 be considered a cloud distribution. The most conspicuous nebula 

 cloud in the northern sky has its centre not many degrees from 

 the pole of the galactic plane. But the centre is quite decidedly 

 not at the pole, and the distribution is very far from being 

 symmetrical about the pole. A second, less rich, cloud of nebulae 

 in the northern hemisphere runs up to the borders of the Milky 

 Way. 



In the southern hemisphere the distribution of nebulae is 

 dominated by the greater Cloud of Magellan, which is far richer in 

 nebulae than any other part of the sky. The distribution of 

 nebulae outside this cloud has no apparent relation to the southern 

 galactic pole, but is in several large and not well-defined clouds. 

 It appears, in fact, that the idea that nebulae are condensed about 

 the poles of the Milky Way may be due to a fortuitous and not 

 very close approximation of one nebula cloud to the place of the 

 northern galactic pole. 



Unfortunately we have at present no knowledge whatever of 

 the distances or proper motions of the nebulae, and conclusions as 

 to their distribution may be profoundly modified when the smaller 

 nebulae which have recently been found in abundance on long 

 exposure photographs are classified and catalogued, and when the 

 already known and catalogued nebulae of the southern sky are 

 classified photographically. It is here suggested that the distri- 



