GASEOUS SPECTRA UNDER HIGH DISPERSION. 437 



In my own finally reduced plates it measures 4 - 3 inches across, and shows 

 no less than 44 distinct and positive lines. 



But in the original records of my spectroscope, and which alone I would 

 desire to refer to now (see Plate LXXVIIL), the breadth of the peninsula is 

 upwards of 264 inches; and though it shows only the same 44 lines just 

 alluded to, — yet it gives them with a force, a character and an effect that can 

 be attained on no smaller scale ; and was the practical mean by which many of 

 them were first discovered to exist. 



Though speaking of these 44 luminous existences as lines, yet it is to be 

 remembered that they are nothing but the linelets composing what appears in 

 smaller instruments a smooth shaded band ; and with my largest spectroscope, 

 it was the most extraordinary thing to contemplate the broad fields of absolute 

 blackness that separated each one of these vivid, hard, sharp -edged, well-defined 

 lines from its nearest neighbour on either side. 



Nor was it less instructive to use a tube containing both CH and CO; and 

 then compare in the same field of view these two opposing principles, as it 

 were, of the Physical world. The unoxidised against the oxidised; the fuel 

 still to burn, against the refuse of fuel long since burnt; this latter the condition 

 of the whole surface of our planet, rocks and water alike, excepting only its 

 coal beds and a little amount of gold and other unoxidisable metals. 



The green CH band comes in (as will be very clearly seen in Plate LVIII.) 

 just on the right of the green peninsula of pure CO; and with its doubled 

 Green-Giant line of CH, shines gloriously enough, but yet with a suspicion of 

 haziness along its edges; while its closely packed following CH linelets, though 

 sometimes exquisitely defined, have something of a gossamer weakness and 

 transparency of look. They are like mere filaments of silk, or spider lines at 

 the best ; and if doubles are seen amongst them occasionally, it arises probably 

 from a process of decomposition having set in, or Hydrogen freeing itself from 

 all earthly contamination; a liliputian curiosity in a vacuum tube, but the chief 

 acting agent in the mighty red prominences of our Sun, and in the terrific 

 conflagrations of so called new, or temporary, stars. 



With CO on the other hand, and its CO linelets, which are the best defined 

 and hardest of diamond-like lines in structure, — if you see them once, you see 

 them always ; fixed like the rocks ; or even growing in their places ; for when 

 once Oxygen has got hold of any Carbon, all the further actions of the 

 illuminating spark seem only to enable it to go on taking an equally firm hold 

 of all the rest of the carbon that may be within its reach. 



In fact, while the usual mode of failing for any CH tube by powerful 

 sparking is to end in its showing nothing but H lines, so for tubes containing 

 any compound of Oxygen, it is to finish by showing nothing but the CO 

 spectrum. And if it has been said, that in the event of a solar conflagration 



