of Edinhuryli, Session 1883-84. 
699 
foreign intrusion of any kind, right up to the Blue band, — save, 
that shortly before that notable Spectrum milestone was reached, a 
faint, but extensive grey cloud was passed ! 
What could that mean ? It proved to be the then broadened or 
hazy condition of the usually sharp line known as Glaucous Hydrogen. 
Minute by minute that cloud brightened and narrowed, while the 
CH linelets continually paled ; and after an hour’s sparking the H, 
of the once CH, had come out in lines everywhere ; while its C was 
deposited as a brown glazing on the inside of the tube ; and my 
beautiful example of a perfect CH spectrum was gone for ever. 
But if we bear in mind how II behaved with regard to C therein, 
and compare that presently with the actions of 0 (Oxygen) in the 
same relation, the experience will be well worth the price paid for 
it. For the chemical interpretation of those spectra is still under 
perfectly radical disputation. 
The CO Spectrum. 
A CO spectrum is easily procured, and with the smallest charge 
of either Carbonic Oxide or Carbonic Acid. Moreover, it remains 
and even improves by use. 
At first sight, the CO spectrum is superficially much like the CH, 
inasmuch as it is a spectrum of coloured bands, intense towards the 
red, vanishing towards the violet. But there are more of them, and 
they have no leading lines in them like the CH, being composed of 
linelets only. 
Moreover, every such linelet is of a different constitution; for 
while those of CH are weak and semi-transparent like spider-lines, 
the CO are hard, sharp, and densely metallic. 
In fact, in place of both of them being spectra of one and the 
same simple element C (Carbon) as usually held in London, I may 
rather say that we are in presence, before them, of two most opposite 
principles of the physical world. The H, in CH, always trying to 
free itself from contaminations of every earthy matter ; but the 0, 
in CO, taking hold of everything near it, and of C most particularly. 
Whence it comes that CH tubes generally end in showing only II ; 
whereas some other tubes, begun with a different gas, end in showing 
nothing but CO. 
Or if that is a petty scale on which to allude to the actions of 
