352 Hartiry ann Ramace—Banded Flame-Spectra of Metals. 
THE ILLUSTRATIONS, AND DESCRIPTION OF PLATES. 
Tue banded spectra yielded by the flame may be distinguished in the engravings by being three or four 
times as broad as the spark-spectrum, which, in every case, was photographed upon them. The spark- 
lines are taken from electrodes of cadmium-tin and cadmium-lead alloys, and are accompanied by air-lines ; 
the wave-lengths of the metallic-lines and air-lines are accurately known, and from them the scales of 
waye-lengths have been drawn. 
The less refrangible end of each of the flame-spectra is shown by the sodium lines; in the case of the 
lithium spectrum these have expanded into a band by reason of sodium being contained in the lithium 
nitrate, from which the spectrum was taken. The red, orange, and blue lines of lithium are well shown, 
and serve to indicate the facility with which they may be photographed when the quantity of substance 
in the flame is not too small. 
Where there is no space for the wave-length numbers to be inserted immediately above the spectra, 
the scale is indicated, upon a faint horizontal line, by short lines. 
Of the group—copper, silver, and gold—silver has already figured in ‘‘ Flame-Spectra” (Phil. Trans., 
1894), and the lines and bands have been measured; copper, as copper oxide, has also been measured and 
described, but the gold spectrum is an entirely new one. The former measurements of the silver spectrum 
may differ slightly from those more recently made, not because they are less accurate, but by reason of the 
bands differing in width, or the intensity and breadth of the lines composing the bands varying either with 
the quantity of substance in the flame, or with the length of time during which the plate was exposed. 
PLATE XXIX. 
1. Gorv, . . This spectrum is quite free from any trace of silver, copper, lead, or other impurities, 
except the sodium lines and the water-vapour lines beyond wave-length 3450, 
which appear, more or less, in all the spectra. 
2. Stnver, . . The flutings between wave-lengths 4000 and 3700 are not so well shown as in the 
illustration to ‘‘ Flame-Spectra,” Part 1., Phil. Zrans., 1894. 
3. CoprEr. 
PLATE XXX. 
4. Capmium, . Detail not sufficiently strong to be reproduced with a distinctness equal to that 
seen in the original photogr aphs. 
. ZINC. 
i) 
6. Magnesium. 
7. Lirmium, . From the nitrate. The sodium-lines have broadened out to a band. 
PLATE: XX XT. 
8. THaLiium, 
| The broadening out of the lines in these spectra is well seen, but faint bands have 
9. InpIum : : : 
J | not been reproduced in the engraving. 
10. Gaxiium, 
11. Atumintum, . Besides the fluted spectrum, there is a band of continuous rays caused by the white- 
hot alumina. 
PLATE XXXII. 
12. Arsenic, . The continuous spectrum, and the bands beyond wave-length 3000, are due to arsenic. 
13. Mercury, . ‘he lines seen are due to sodium, potassium, calcium, and iron. 
14. Motyspenum, From molybdenum trioxide. 
15. LanrHanum. 
PLATE XXXIII. 
16. Inrpium, . There are several bands composed of lines, and some lines independent of bands, in 
this spectrum. 
17. Patapum, . A number of strong lines accompany the bands in this spectrum. 
