248 THE NEBULAR IirPOTIIESIS. 



ameter into twenty thousand starry points. At the same 

 time that the individual stars of a nebula eight minutes in 

 diameter are 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 diffi- 

 culty is presented by the phenomena of the Magellanic 

 clouds. Describing^ the laro-er of these, Sir John Herschel 



" The nubecula major, like the minor, consists partly of large 

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

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

 like the Milky "Way ; as also of regular and irregular nebuli© prop- 

 erly so called, of globular clusters in every stage of resolvability, 

 and of clustering groups sufliciently insulated and condensed to 

 come under the designation of ' cluster of stars.' " — " Oape Ob- 

 servations," p. 146. 



In his " Outlines of Astronomy," Sir John Herschel, af- 

 ter repeating this description in other words, goes on to 

 remark that — 



" This combination of characters, rightly considered, is in a 

 high degree instructive, afi'ordlng an insight into the probable 

 comparative distance of staj^s and nebulce^ and the real brightness 

 of individual stars as compared with one another. Taking the 

 apparent semi-diameter of the nubecula major at three degrees, 

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

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

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

 The brightness of objects situated in its nearer portions, there- 

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

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

 lar space we have collected upwards of six hundred stars of the 

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



