Ixvi President's Address 



refractor. Mr. Abbott also made some drawings from 

 observations with a 4J in. refractor and Lieut. Herschel by- 

 aid of a 12 in. reflector. They have all indicated that the 

 general appearance of the nebulae differed considerably from 

 that represented by Sir John Herschal's drawings, although 

 none of the apertures used could in any way pretend to 

 reach the more minute details grasped by Herschel's 2 ft. 

 reflector. Several of the drawings which reached home had 

 evidently not been executed with that precision which is so 

 necessary to establish a fact of this kind in the minds of 

 astronomers who are unable to see for themselves. There 

 has arisen, therefore, in the minds of many of our most 

 renowned observers in England and elsewhere, doubts as to 

 the real existence of these changes. For it must be 

 remembered that the immense distance of the nebulae from 

 us — probably far beyond the most distant stars — makes it 

 necessary that changes such as these described, to be visible 

 to us even with the aid of such light-gathering apertures 

 and optical power as is possessed by our large telescope, 

 must be stupendous in the highest degree and almost 

 beyond comparison with the more ordinary cosmical 

 changes with which we are familiar. 



Now, since the great telescope has been erected special 

 attention has been given to this object. Mr. Le Sueur 

 devoted a great deal of time, extending over long periods, 

 to examination and drawings, repeating his observations again 

 after the lapse of many months. He constantly referred to me 

 to establish or throw doubt on his observations, so that I 

 often observed with an unbiassed eye for this purpose. The 

 stars down to the 16th magnitude were carefully plotted 

 (those to the 12th magnitude with the micrometer), to form 

 an unchanging groundwork for the mapping. He announced 

 on several occasions in this Society and elsewhere that there 

 wei'e unmistakable chansfes since Sir John Herschel's drawings 



