Band and Line Spectra of the same Metallic Elements. 123 
The series of bands between dd 4700 and 4300 is well shown on the photograph. 
The silver lines \A 3383 and 3280°8 are each at the head of a fine composite band 
consisting of a number of fine lines. On p. 167 of ‘ Flame-Spectra at High 
Temperatures” I have described how these two lines correspond with two in 
the spark spectrum, their wave-lengths being 3382°6 and 8280:45 respectively 
(Hartley and Adeney), and how they appear as fine lines when the silver is diluted 
with some other metal and volatilized in the oxyhydrogen flame. ‘This is shown 
on Plate 7 of the same publication in the spectrum of bismuth, and the lines have 
the same appearance when lead, copper, or other metals, ores, or minerals are 
examined in the same manner, if they contain traces of silver. This has been 
observed in some hundreds of substances. It will be easily understood from an 
inspection of the engraving (2 Silver) on Plate XXIX. of “‘ Banded Flame Spectra 
of Metals,”* how impossible it is to obtain accurate measurements which are 
concordant when varying quantities of silver are volatilized, inasmuch as the 
lines become converted into bands which are developed more on the side of the 
less refrangible rays. 
The same observation applies to band spectra in general; they are not under 
all conditions bounded by the same rays of definite wave-lengths, but vary in 
width and intensity with the conditions under which the substances from which 
they originate are vapourized. 
The measurements quoted for comparison in the present communication were 
made from a much stronger spectrum than those taken from spectra representing 
weighed quantities of metal. The exposure of the photographic plate was longer 
also. It is also to be noted that the plates of Wratten and Wainwright used 
latterly are much more equally sensitive throughout the whole spectrum than any 
which could be obtained previously, so that lines as far down in the red as 
\ 7665°6 appear. ‘This admirable quality also serves to modify the spectra. 
The composite band is extinct when only 0:1 gr. of silver is present in the 
flame, but the diffuse bands are still faintly visible, and the two lines at the heads 
of the composite bands are also visible. 
CopPER. 
The salt used was Cu (NO;),° H,O. Photographed with Wratten and 
Wainwright’s panchromatic plates. 
Quantity of Description of Spectrum. 
Copper. 
0°5 gr. in 5 A beautiful banded spectrum, extending from the yellow 
portions. sodium lines into the blue. There are five series of bands— 
(1) Between 5100 and 5800, a broad band of equal intensity on either 
side, but composed of a number of diffuse and very narrow bands. This band 
* Hartley and Ramage, Scient. Trans. Roy. Dublin Soc., 2, vol. vii., pp. 339-352. 1901. 
