248 THE NEBULAli IliTJ OTHESIS. 



aractcr into twenty thousand starry points. At the same 

 lime that the individual stars of a nebula eight minutes in 

 diameter arc so clearly seen as to allow of their number 

 being estimated, a nebula covering an area five hundred 

 times as great shows no stars at all. What possible expla 

 nation can be given of this on the current hypothesis ? 



Yet a further difficulty remains one which is, perhaps, 

 still more obviously fatal than the foregoing. This diili- 

 imlty is presented by the phenomena of the Hagellanic 

 clouds. Describing the larger of these, Sir John llerschel 

 says : 



u The nubccula major, like (ho minor, consists partly of large 

 tracts and ill-defined patches of irresolvable nebula, and of nebu 

 losity iu every stage of resolution, up to perfectly resolved stars 

 like the Milky AVay; as also of regular and irregular ncbuko prop 

 erly so called, of globular clusters iu every stage of rcsolvability, 

 and of clustering groups sufficiently insulated and condensed to 

 come under tlio designation of cluster of stars. &quot; u Capo Ob 

 servations,&quot; p. 140. 



In his &quot; Outlines of Astronomy,&quot; Sir John llerschel, al 

 ter repeating this description in other words, goes on to 

 remark that 



&quot;This combination of characters, rightly considered, is in a 

 high degree instructive, affording an insight into the probable 

 comparative distance of stdrs and nebular, and the real brightness 

 of individual stars as compared with one another. Taking tho 

 apparent semi-diameter of tho nubccula major at three degrees, 

 and regarding its solid form as, roughly speaking, spherical, its 

 nearest and most remote parts differ in their distance from us by 

 a little moro than a tenth part of our distance from its centre. 

 Tho brightness of objects situated in its nearer portions, there 

 fore, cannot bo much exaggerated, nor that of its remoter much 

 enfeebled, by their difference of distance. Yet within this globu 

 lar space we liavo collected upwards of six hundred stars of tho 

 seventh, eighth, ninth, and tenth magnitude, nearly three hundred 



