foT the year 1872. Ixvii 



Mr. MacGeorge, who succeeded Mr. Le Sueur, and who has 

 also observed and drawn the nebulae constantly, pointed out 

 to you in his paper in October last the progressive changes 

 that had been noted. The diagram he then exhibited I had 

 photographed and sent home to Dr. Robinson (one of the 

 Great Telescope Committee), with a copy of Mr. MacGeorge's 

 paper. The paper got home first, and Dr. Robinson says, in 

 a letter I received last mail, " I lose no time in forwarding 

 the paper to Sir E. Sabine, Mr. Lassell, and Mr. Warren De 

 La Rue. . . . Mr. Lassell seems to cling to the idea 

 which he published some time ago, that there was no 

 change whatever in Eta Argus. He justifies this suspense of 

 opinion by not being able to refer to the drawings, a 

 difficulty which I hope you will soon be able to remove. I 

 think his real difficulty is an opinion that nebulae must be 

 at a distance much greater than that even of small stars, 

 and hence an incapability of conceiving the possibility of 

 such changes as could be visible to us." The photographs 

 reached him by next mail, and he then writes—" The 

 photographs are very remarkable, and I think it is im- 

 possible to look at them and doubt the reality of the 

 immense changes that have taken place. Are these changes 

 periodical 1 I send one of the photographs by this post to 

 Sir Ed. Sabine, with request to forward it to Messrs. Lassell 

 and De La Rue." 



It is to be regretted that the minute and careful draw- 

 ings made by Messrs. Le Sueur and MacGeorge have not 

 yet been engraved, as they establish the fact beyond all 

 doubt, as the photographs sent home were from a some- 

 what rough diagram intended only to show the principal 

 features of the observed changes. No one accustomed to 

 observing could fail to be convinced of change going on 

 if he only saw the nebulae with a power of six or seven 

 hundred on the great telescope on good nights at intervals 



F 2 



