SECT. XXXVI. MILKY WAY. 385 



magnitude is 100 times less than that of one of the first magni- 

 tude, and that Sirius would make between three and four 

 hundred of such little stars. Were the photometric scale com- 

 pleted, it would be of the greatest importance with regard to the 

 variable stars. 



The three or four brightest classes of stars are scattered pretty 

 equably over the sky, with the exception of a zone or belt fol- 

 lowing the course of the great circle passing through e Orionis 

 and a Crucis, where they are very numerous, especially in the 

 southern hemisphere. The stars of all magnitudes visible to 

 the naked eye increase in numbers towards the borders of the 

 Milky Way, which derives its lustre and name from the diffused 

 light of myriads of stars ; so numerous are they in some parts 

 of it that more than 50,000 passed through the field of Sir 

 William Herschel's telescope in the course of an hour, in a zone 

 only two degrees broad; in many places they are numerous 

 beyond estimation, and most of them are extremely small on 

 account of their enormous distances. 



The Milky W T ay, which forms so conspicuous a part of the 

 firmament, is a vast and somewhat flattened stratum or con- 

 geries of stars, encircling the heavens in a broad band, split 

 through one part of its circumference into two streams of stars, 

 bearing a strong resemblance to fig. 5, plate 5. It is contorted 

 and broken in some places, and occasionally lengthened into 

 branches stretching far into space. Its thickness is small com- 

 pared with its length and breadth ; yet in some places it is un- 

 fathomable even with the best telescopes ; in others there is 

 reason to believe that it- is possible to see through it, and even 

 beyond it, in its own plane. There is a gradual but rapid in- 

 crease in the crowding of the stars on each side of the flat stra- 

 tum towards the centre. 



The solar system is deeply'though excentrically plunged into 

 this- mass of stars, near that point where the circular stratum 

 splits into two streams. Sir John Herschel's description of the 

 stars of the southern hemisphere shows that the Milky Way is 

 a most magnificent object there. " The general aspect of the 

 southern oircumpolar regions (including in that expression 60 

 or 70 of south polar distance) is in a high degree rich and mag- 

 nificent, owing to the superior brilliancy and large development 

 of the Milky Way, which, from the constellation of Orion to 



