30 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



known influence which goes through its period in nearly a 

 year. The main result of Nyren's investigation, namely, for 

 the constant of nutation, the value 9.2365", is so nearly the 

 same as that of Peters' published in 1842, that it is not likely 

 that the value which is now in use will be discarded, for the 

 present at least. 



GREAT NEBULA IN ARGUS. 



The interest in the study of nebulte, which received so 

 strong an impetus by the construction of the great reflectors 

 of Herschel and others, continues to be fostered by the per- 

 petual attention given to those bodies by the possessors of 

 the giant refractors and reflectors of the present day. Per- 

 haps no celestial object, except the sun, has been during the 

 past few years examined with more interest than the great 

 nebula surrounding Eta Argus. This nebula was first care- 

 fully examined by Sir John Herschel, in 1834 to 1839, when 

 it was quite invisible to the naked eye, and his drawings and 

 descriptions contain our first exact knowledge of this object, 

 which can only be well seen from the extreme southern ob- 

 servatories. No special drawing seems to have been made 

 by other astronomers until 1862, when Mr. Abbott, an am- 

 ateur residing at Hobart-Town, Tasmania, made drawings, 

 which he has since then frequently verified and repeated ; 

 and in 1865 he announced the fact that great changes had 

 taken place and were in progress in this nebula. So unex- 

 pected and novel were the ideas thus promulgated that they 

 found very few adherents, the more so as Mr. Abbott was lit- 

 tle known, and his telescope was of but moderate power. 

 Indeed, a very unpleasant and uncalled-for feeling arose, as 

 if Mr. Abbott had questioned the accuracy of Herschel's elab- 

 orate drawings, which he in nowise did. In the midst of 

 this discussion there arrived at Melbourne the magnificent 

 four-foot reflector that had given such perfect satisfaction in 

 England at its trial, and of whose powers so much was to be 

 expected. The result of the examination o^ Eta Argus was 

 in the highest degree disappointing, which may have been 

 partly owing to a deterioration of the reflecting surface of 

 the great mirror, and probably was also somewhat due to the 

 peculiarities of the atmosphere of Melbourne and to the inex- 

 perience of the observers. Indeed, Mr. Abbott, who visited 



