142 PROFESSOR PIAZZI SMYTH ON 
APPENDIX IL. 
TABLES OF GASEOUS IMPURITIES, THEIR CHARACTERISTICS AND 
ELIMINATIONS. 
This enquiry is followed out in these tables in conjunction with the search for, or identification 
of, new lines in various of the gases: the main principle assumed being, that any new or faint line of 
any gas, ought to be more or less visible in every tube, according to the visibility therein of the 
brighter known lines of that gas. 
With Hydrogen therefore (whose four standard lines there is no question about as to place),— 
I have begun its tables, with four double columns giving both a numerical expression for the intensity 
of its appearance, and a graphical reminder of the shape thereof, in each of the said four lines, in 
every tube observed. The Hydrogen tube, where alone these lines have full right to appear, has its 
number printed in the heaviest type. Other tubes which have hydrogen in their chemical composi- 
tion associated with something else, have their numbers printed in less heavy type: but the tubes 
where the alleged contents have no chemical claim whatever to hydrogen, and yet show its spectral 
lines, have their numbers given in thin type. 
Hence it may easily be seen, but with some surprise, that Oxygen and Ozone tubes show, besides 
their own lines, those of Hydrogen with even maxmimum force, though no Hydrogen ought to be 
there. Much Hydrogen appears also in Alcohol and Ammonia, but their compound formations claim 
Hydrogen as one of their constituents. Olefiant-gas and Marsh-gas have the same right to Hydrogen, 
but do not show so much of it in pure Hydrogen lines; partly perhaps because some of it is retained 
with them to show the perfectly different lines of Carbo-hydrogen compound, or what is seen in the 
base of ordinary coal-gas flames. 
Turning then to, say the hitherto unclaimed line at 43 698 W.N. Place, and finding it strong in 
Hydrogen, Oxygen, Ozone, Olefiant-gas, Nitrogen, Marsh-gas, Alcohol, Ammonia, and all the tubes 
which have the known Hydrogen lines strong,—but absent in Chlorine, Cyanogen and others, when 
the known Hydrogen lines are either completely, or nearly absent,—we may say that we find the 
above hitherto unclaimed line appearing everywhere as a function of Hydrogen; whence we seem 
entitled to claim it here as one of our new, low-temperature, lines of Hydrogen. 
