60 Comparison of Sun and Stars. 



experience has led me to believe that a much smaller aperture 

 than that of ten inches specified by 0. Struve, as quoted in my 

 former paper, is competent to deal with a fair proportion of 

 its most remarkable features, and that many of our readers 

 might find it highly interesting to make it matter of careful 

 examination, and to record what they see for future comparison. 

 To prepare for this by a wholly independent process of mapping 

 out the included and attendant stars, would be not only very 

 laborious, but a great waste of time, when a simple diagram will 

 supply everything of the kind. Such a design is here given, 

 inverted of course to suit the astronomical eye-piece ; and a 

 copy of it, especially if upon an enlarged scale, will serve at 

 once as the groundwork of a delineation of the nebula. 



The stars are by no means all that are visible with a 5 1 -inch 

 object-glass, bat they are such as seemed at once the most 

 obvious and the most favourably situated; some pains have 

 been taken with their relative magnitudes, but accuracy will 

 not be expected ; and the lines indicating the position of the 

 nebulosity are inserted merely for more convenient identifica- 

 tion, and should be omitted in preparing the copy for use. It 

 may require a little perseverance, and the employment of 

 various magnifiers (even high ones not being excluded), to 

 make out the boundaries and details of the hazy mass, but habit 

 will soon render its aspect familiar, and more intelligible than 

 might have been at first expected. Attention may be particu- 

 larly directed to the arrangement of the " flocculi/' or cloudy 

 wisps, in the bright region lying S. of the trapezium, as here 

 they are most distinct, and appear to me to exhibit the least 

 agreement with the published designs of our great observers ; 

 and should the attempt at delineation at first seem difficult or 

 uninteresting, we may call to mind that within a short time, on 

 this spot rather than anywhere else in the heavens, is one of 

 the most remarkable of all astronomical enigmas likely to 

 receive its solution — what is the true character of many of the 

 nebulae ? Are they merely remote collections of stars ? or are 

 they luminous mists, of a nature wholly unknown, and subject 

 to internal movements whose causes are now, and probably 

 will ever remain, us Seneca says, "hidden in the majesty of 

 nature " ? 



COMPARISON OP SUN AND STARS. 



Tin; celebrated American optician, Alvan Clark — whoso 

 gigantic 18|-inch object-glass, after receiving the Lalande 

 prize of I he Academic des Sciences, has recently been pur- 

 chased by the Astronomical Association of Chicago for 11,187 

 dollars — has published an interest ing account of his photometric 

 experiments on (lie comparative brightness of the sun and the 

 fixed stars.* Starting with the acknowledged optical fact, that 



* The Sun and Stars Photometric ally Compared. By Alvan Clark. 1863. 



