420 Gautier on Nebulce. 



first sketched as a light object on a dark ground, and then as a 

 dark object upon a light ground. 



The general aspect of the greater part of the nebula as thus 

 depicted, was that of an assemblage of tufts or curved bunches 

 of luminous matter emanating from the brilliant masses near 

 the trapezium, extending towards the south on each side of an 

 axis, passing by the top of the region of Huyghens, and whose 

 angle of position is nearly 180°. Twenty of these circumvolu- 

 tions were distinctly traced, while others, producing the same im- 

 pression, are too faint or too complicated to be described with 

 precision. Thus the nebula of Orion belongs to the spiral class. 



Mr. Bond noticed many cases in which masses of nebulous 

 matter were associated with stars, frequently under the form of 

 little tufts extending from the south side. He likewise cites 

 two remarkable instances of a deficit of luminous matter close 

 to tolerably brilliant stars. The first occurs in the trapezium 

 itself, the dark centre of which has been noticed by many ob- 

 servers, and the other belongs to the star u (iota). Mr. Bond 

 inclined to the idea that there was a physical connection be- 

 tween the stars and the nebulosity. The spiral form accorded 

 with the notion of a stellar arrangement, as shown in a mass 

 of stars, properly so called, in the constellation Hercules, which 

 have evidently a curvilinear disposition. 



In 1860, Mr. Norman Pogson observed a change in the 

 nebula or mass of stars in Scorpio (No. 80 in Messier' s cata- 

 logue). On the 9th May, this nebula had its ordinary aspect, 

 without any stellar appearance, and on the 28th of the same 

 month, he noticed in it a star of 7th or 8th mag., which was 

 also seen on the 21st at Konigsberg by MM. Luther and 

 Auwers, and estimated by them as below the 7th mag. On 

 the 10th of June following, under a power of 66, the star appear- 

 ance was almost invisible, but the nebula glowed with more than 

 ordinary lustre, and with a well-marked central condensation. 

 Mr. Pogson did not attribute this variation to a change in the 

 nebula itself, but thought it singular that a new variable star, 

 the third comprised in the same field of vision, should be found 

 situated exactly in the centre of this nebula. 



More recently, M. Chacornac has observed the annular 

 nebula in Lyra with the great Foucault telescope, and he has 

 confirmed its resolution into a mass of minute stars, the most 

 brilliant occupying the extremities of the inner axis. This 

 nebula looked like a hollow cylinder seen in a direction nearly 

 parallel to its axis, with its centre, as described by Lord Rosse, 

 veiled by a curtain of nebulous matter which was transformed 

 into a thin layer of little stars. When all other light was ex- 

 cluded, M. Chacornac found that the scintillation of this multi- 

 tude of luminous points produced a singular effect of giddiness. 



