A. MATHEMATICS AND ASTRONOMY. 31 



Melbourne for the special purpose, states that he was much 

 surprised himself on seeing Eta Argus in such a small field 

 of view with so larije an instrument, whence Ave infer that it 

 had appeared very different when viewed through his own 

 telescope. The drawings of Lieutenant A. S. Herschel, made 

 at Bangalore in 1868, and the report of Le Sueur, the first ob- 

 server in charge of the Melbourne telescope, in 1871, seemed 

 to further complicate the question of the reality of a change 

 in the nebula. But the present observer at Melbourne, Mr. 

 M'George, the director, Mr. Ellery, and also the government 

 astronomer of New South Wales, Mr. Russell, have each made 

 drawings of the nebula, and these, with the drawings of 

 Mr. Abbott, made in 1871, fully establish the existence of 

 o-reat chanfjes, as follows : 1. The brightness of the nebula 

 has increased so much that it has become visible to the naked 

 eye. 2. The bright star Eta Argus is now thrown upon a 

 darker background, instead of being in the brightest part of 

 the nebula. 3. Numerous stars are now present which were 

 not before visible. 4. The brightness of a number of stars, that 

 were before much fainter than the principal star, has increased. 



Mr. Abbott states that in the same field of view with Eta 

 Argus there are now twenty-four stars of the sixth, seventh, 

 and eiirhth maccnitudes, and an immense number of fainter 

 ones. The most recent communication by Mr. Abbott on 

 this subject summarizes the results of his observations as fol- 

 lows : In the eye draft of the object Eta Argus^ February, 

 1873, the principal stars appear to have retained their relative 

 position as shown in the drawings of last year. The dark 

 spaces are extending and becoming more undefined, gradually 

 filling up with small stars, of which there are now fully half 

 as many more as Avere shown in last year's drawing. 



The Avhole field of the telescope when directed to Eta Ar- 

 gus is studded with stars, from the seventh to the tenth mag- 

 nitude, too numerous to count. In all probability before long 

 photography Avill be applied to this and other portions of the 

 dense nebula. Monthly Not. Hoy. /Soc. of Tasmania. 



schroeter's observations of mars. 



Terby, in some researches on the physical changes in the 

 planets of the solar system, has come upon a mass of impor- 

 tant unpublished observations by the famous Schroeter. 



