418 Gautier on Nebulce. 



GAUTIER ON NEBULA. 



The jBibliotheque Universelle et Revue Suisse has an' interesting 

 article by Professor Gautier on Nebulas, of which the following 

 is a condensed account : — 



The author begins by stating that his purpose is to give 

 " a slight idea" of a wonderful class of objects which have been 

 specially studied by the two Herschels, Messier, Lord Rosse, 

 Vico, Secchi, Lamont, Lassell, and Bond, and of which fifty- 

 three have been accurately placed in M. Langier's catalogue, 

 published in the Comptes Mendus of 12th December, 1853. 

 This list gives the positions of the nebulas with great nicety, 

 and thus lays a foundation for deciding whether they are really 

 situated beyond the fixed stars that are visible to us. 



The Orion nebula formed the subject of a paper presented 

 through M. Struve to the St. Petersburg Academy in 1856, 

 and which detailed the results of four years' investigations, 

 conducted by M. Liapounoff (Director of the Kasan Observatory), 

 with an equatoreal telescope, equal to that of Dorpat, and a 

 meridian circle of Repsold. M. Liapounoff noted down the 

 position of every star he could distinguish in this nebula, and 

 in comparing his accounts with those of Sir J. Herschel and 

 Messrs. Lamont and Bond, M. Struve came to the conclusion 

 that it must be subject to changes of form, and of the relative 

 brightness of its different parts. 



At Poulkova M. Otto Struve continued the work of M. 

 Liapounoff, as recorded in the Monthly Notices of tbe Astrono- 

 mical Society for 1857. M. Struve pointed out the variable 

 light of divers little stars, and he observed : " The existence of 

 so many variable stars in so small a space of the central part 

 of the most curious nebula in the heavens, naturally induces us 

 to suppose that these phenomena are intimately connected with 



the mysterious nature of this body In admitting 



that the rapid changes of light observed in these little stars, 

 whether in the region called Huyghens or that termed Subnebu- 

 losa, are connected with the nature of the nebula, we may pre- 

 sume that we should equally observe changes in the appearance 

 of the nebula, and in the distribution of the nebulous matter; 

 but observations of this kind are subject to so many illusions 

 that we cannot be too cautious." Among causes of discrepancy 

 between different observations, he enumerated the power of the 

 telescope, the state of the atmosphere, the eye of the observer, 

 and his experience in producing graphic delineations of this 

 kind of object; which, taken altogether, precluded any cer- 

 tain discovery of changes of a progressive character that might 

 occur in short spaces of time. It is, therefore, towards rapid 



