386 Notices respecting Nexv Books. 



vails. If we except the two Nubeculse (which are full of nebulae, 

 and the greater part of which is even richer in objects of that class 

 than the densest portion of the northern group), the general character 

 of this hemisphere is that of altcj-nating patches of nebulae and va- 

 cuities of greater or lesser extent, some of the latter however being 

 very extensive. In one of these vacuities, in which comparatively 

 few nebulae occur, the south pole is situated, having one nebula, 

 however, within half a degree of it (as the north pole has also one 

 within five or six minutes). This barren region extends nearly 15° 

 on all sides of the pole, and immediately on its borders occurs the 

 smaller nubecula. 



" One of the most remarkable features in the southern nebulous 

 system is the extraordinary display of finely resolved and resolvable 

 globular clusters which occurs between 16'' 45"^ and 19'' in RA in 

 the region occupied by Corona Australis, the body and head of Sagit- 

 tarius, the tail of Scorpio, with part of Telescopium and Ara. Here, 

 in a circular space of 18° in radius, we find collected no less than 

 thirt}- of these beautiful and exquisite objects. This is certainly 

 something beyond a mere accidental coincidence. Are we to sup- 

 pose that in this direction the visual ray encounters some branch of 

 the general nebulous system nearer to us than the rest ? Or are we 

 to connect it with the very peculiar structure of the Milky Way in 

 this particular part of its course, which is here unlike in its consti- 

 tution to any other portion of that zone, and which passes dia- 

 metrically across the circular area in question } It can hardly be 

 doubted that some at least of these objects belong to and form a part 

 of the Milky Way. 



" The general conclusion which may be drawn from this survey, 

 however, is, that the nebulous system is distinct from the sidereal, 

 though involving, and perhaps, to a certain extent, intermixed with 

 the latter. I'he great nebulous constellation in the northern hemi- 

 sphere, which I have called the region of Virgo, being regarded as 

 the main body of this system, and subtending at our point of view 

 an angle of 80° or 90°, it is evident that, supposing its form to 

 approach to the spherical, our distance from its centre must be con- 

 siderably less than its own diameter, so that our system may very 

 well be regarded as placed somewhat beyond the borders of its 

 denser portion, yet involved among its outlying members, or forming 

 an element of someone of its protuberances orbranchee of which the 

 individuals are the sporadic nel)ulae confusedly scattered over the 

 general surface of the heavens, and of which the prolongation in a 

 direction towards the constellation Pisces may give rise to the appa- 

 rently denser grouping of the nebulae in that region." — P. 136. 



The author next treats of the "Classification of Nebuhe." He 

 observes that " the distinction between nebulae and clusters of stars 

 must depend on two very different considerations: — 1st, on the 

 power of our instrument to distinguish the very minute individuals 

 of which a resolvable cluster, or one entirely composed of stars, may 

 consist; and 2nQly, on the idea we attach to the word ' nebulous,' 

 that is to say, on the distinction which we conceive to exist between 



