Referee report by T. R. Robinson on 'On the Spectra of Ignited Gases and Vapours, with Especial Regard to the Different Spectra of the Same Elementary Gaseous Substance' by J. Plücker and J. Hittorf

                                of a Geisler tube, those of the second by that of a Leyden 
jar if the density <s>[text?]<\s> exceed two or three inches 
of mercury; if <s>that <\s> the gas be more rarified the spectrum 
is of the first kind. These two kinds, I may remark 
I have described as occurring in the gases which 
I examined at common pressure and one at two 
tenths of an inch; but Dr Plucker has not detected 
the remarkable Transition spectrum which is the 
link between them, and in which with some electrodes 
almost every line vanishes. He refers these changes 
to the effect of difference of Temperature, which he 
thinks produces several <s>different <\s> Allotropic states 
of the gas, which cease the instant the discharge has 
passed, and in virtue of which its incandescence 
gives out different sets of rays. He suggests as 
another explanation that the discharge may decom =
pose the gas into unknown components whose 
spectra we see, but which instantly reunite. Of the 
two I should prefer this to the other, which reminds 
one of the Occult Qualities of the schoolmen; but we 
are not confined to this Dilemma, and I think we 
are yet far from being in a condition to speculate 
on the causes of these spectral phenomena. Before 
we can do that to any purpose we must collect 
many more facts, and it is the number of these 
contained in this paper, rather than its theories,
which makes it so valuable 
The less pleasing part of my duty remains, to point out 
what seem to me defects 
The English of the paper is very creditable to Dr Plucker 
(who I <s>suppose <\s> believe wrote it); but of course there are words 
which I suppose you will correct. I have marked 
several with pencil 
A scale of some sort should be applied to the maps 
of the spectra; and the bands and lines which are