THE NEBULA IN ANDROMEDA. 79 



It ought, perhaps, here to be observed, that the views of this 

 illustrious astronomer, in later years, received some modification in 

 respect to the nature of many of the nebulae. 



The following is Sir John Herschel's description, in 1826. 



" At present it has not, indeed, a star, or any well-defined disk in its cen- 

 tre, but the brightness, which increases by a regular gradation from the cir- 

 cumference, suddenly acquires a great accession, so as to offer the appearance 

 of a nipple as it were in the middle, of very small diameter (10" or 12"), but 

 totally devoid of any distinct outline ; so that it is impossible to say precisely 

 where the nucleus ends and the nebula begins. 



" Its nebulosity is of the most perfectly milky absolutely irresolvable kind, 

 without the slightest tendency to that se^iaration into flocculi above described 

 in the nebula in Orion, nor is there any sort of appearance of the smallest 

 star in the centre of the nipple. This nebula is oval, very bright, and of 

 great magnitude, and altogether a most magnificent object." 



The following passage, occurring in another connection, may 

 also be cited. 



" The great nebula in Andromeda may be, and not improbably is, optically 

 nebulous, owing to the smallness of its constituent stars." 



In 1836, Dr. Lamont, of Munich, observed it with a refrac- 

 tor of great capacity; under a power of 1200, the diameter of 

 the nucleus was about 1". His description accords with that of 

 Sir John Herschel. 



The mounting of the great refractor of the Cambridge Ob- 

 servatory having been completed in the beginning of July, 1847, 

 an early opportunity was taken of directing it upon the neb- 

 ula in Andromeda, as being an object of prominent interest ; 

 and from that time, through the month of August, it was occasion- 

 ally viewed, though without particular attention. The most con- 



