282 



Gomeiary Light. 



and not reflected light, but even this was a long step in advance, 

 and afforded great promise of future discovery. His very 

 curious diagram is but little known in England, and we shall 

 therefore give a reduced copy of it, which will be the more 

 intelligible and interesting since, chiefly through the enter- 

 prise and perseverance of Mr. Browning, the spectroscope bids 

 fair to become a more popular instrument amongst us ; as it 

 well deserves. 



The uppermost portion of the diagram is the spectrum of 

 the comet, exhibiting the three bright bands ; the lower is the 



corresponding portion of that of 

 the sun, showing the four dark 

 lines, and close groups of lines, 

 named by Frauenhofer D b F and 

 G ; D, the u sodium-line," being 

 to the right-hand. From this it 

 appears that the light of the comet, 

 being coincident with the blue and 

 green spaces of the spectrum, must 

 have had that hue. It may be 

 G F J D presumed, however, that though 



this comet did not reflect solar light, in which case a more 

 continuous spectrum would have been produced, yet its com- 

 position, however analogous, could not have been identical 

 with that of our recent visitant. Mr. Huggins has spoken of 

 the bright lines in the spectrum observed by him as resembling 

 those of some of the nebulas, and taking those of 37 !§. IV. as 

 a specimen (see Intellectual Observer, vi. 402), we find their 

 magnitude and arrangement very different, the whole of the 

 nebular spectrum being comprised within the left-hand half 

 of the space between b and F, and consisting of extremely 

 narrow stripes, perhaps not exceeding one-fiftieth of the breadth 

 of the bands in Donates figure. Unless, therefore, there were 

 some essential difference in the two instruments or modes of 

 observation, it must be inferred that there was a wide dis- 

 similarity in the composition of these two comets. This, of 

 course, might have been expected. A very little attention to 

 the descriptions of former comets would convince us that with 

 complete identity of type there is considerable variety in detail ; 

 and some of these differences are such as to indicate diversity 

 of materials, not merely as between different comets, but as 

 co-existing in the same individual. One very remarkable feature 

 of this kind is the combination of a straight with a curved tail; 

 the one streaming right out into space, and piercing the ether, 

 as it would seem, without resistance ; the other swept back- 

 wards and condensed at its advancing edge, according to 

 Kepler's striking comparison, like the corn in the winnowing- 



