6 Notes on Star- Streams. 



bling that of the solid cloven disc exhibited in Figs. 4 and 5. 

 The latter figure, being a side view, gives the figure of the 



Fig. 4. 



imaginary section which appears so often in works on astro- 

 nomy. In Figs. 3 and 5 the small circle near the centre 

 indicates the probable extent (on the theory in question) of the 

 sphere within which stars down to the fourth magnitude may 

 be supposed to be included. 



The main difficulties in attempting to form an estimate of 

 the real configuration of the galactic nebula are those which 

 have been already mentioned. Have we evidence coufirming 

 or disproving (1) the tendency to clustering suggested by the 

 elder Herschel, (2) the possible variability among star-magni- 

 tudes, and (3) of influences exerted by large stars in guiding 

 or swaying others ? It appears to me that there are indications 

 of a very obvious and important character, which have been 

 either altogether unnoticed, or much less noticed than they 

 deserve. In considering these indications, I would refer the 

 reader chiefly to Figs. 1 and 2 ; but some portions of the 

 evidence cannot be thoroughly understood without reference to 

 star-maps, in which (at a single view, if possible) the course of 

 the Milky Way is exhibited in a manner which enables us at 

 once to determine its relations to the constellations not included 

 in these figures. I write with my black star-maps before me, 

 my object being to consider the special evidence afforded by 

 stars of the leading magnitudes. It may seem (and, indeed, 

 on the assumption of any approach to uniformity in the true 

 magnitudes, or distribution of stars, it must necessarily be) a 

 very imperfect method to refer to star-maps including only the 

 first five magnitudes, still more to consider the first four 

 magnitudes which arc alone represented in Fig. ] . It is 



