14 tj Arg'As and surrounding Nebula. 



The sun is not a case in point, for there the bright and 

 dark lines are not seen together. The former are visible 

 only on a small annulus of the disc, and are due to gases 

 cooler than the continuous spectrum giving nucleus, as 

 proved by the fact that on the surface of the sun the corre- 

 sponding lines are dark. 



In the absence of direct evidence from dark iines in its 

 spectrum, we are unable to tell what are the constituents of 

 Tj Argus, other than those revealed by the bright lines ; on the 

 supposition, however, that the other substances belong to the 

 series already discovered in the sun, stars, and nebulae, it is 

 not unimportant to notice that the constituents of the stars in 

 question more or less certainly indicated by the bright lines 

 would, from mechanical considerations, be high up in its 

 atmosphere. 



Hydrogen (on a supposition) would mount far above the 

 rest at the extreme limits thereof; nitrogen, sodium, mag- 

 nesium would follow next in order. It is probable that the 

 bright line character of the spectrum of -q Argus, indicates a 

 commencement of increase in brilliancy ; whether or not, 

 however, the star at its minimum retains a condition capable 

 of producing such a spectrum, there can be little doubt 

 that the gases to which the now seen bright line belongs, 

 play a prominent part in the star's variability. 



The nebula surrounding 77 Argus has been frequently ex- 

 amined ; its spectrum consists of the three well-known bright 

 lines indicating a gaseous constitution, similar to that of the 

 nebula in Orion. 



The comparison of a sketch representing part of the nebula 

 as seen last year in the Melbourne reflector, with Sir J. 

 Eerschell's Cape drawing has afforded interesting results. 



It is well known by those who have devoted much atten- 

 tion to nebula work, that even from the hands of a most 

 accomplished draughtsman minute details are not to be 

 impHcity trusted ; when, moreover, to the imperfect represen- 

 tation of the eye- view as seen with a particular instrument 

 is added the disturbing effect of difference of aperture, much 

 •caution is required in drawing conclusions from the evidence 

 of observations made with widely different instruments. 



In the case before us the sketches differ very widely, not 

 in minute detail only, but ia general character over a large 

 space. 



In the Cape drawing the star -q is immersed in bright 

 nebula ; as seen with the Melbourne telescope, it lies on a 



