352 



Hartley and Ramage — Banded Flame-Spectra of 3Ieials. 



THE ILLUSTEATIONS, AND DESCRIPTION OF PLATES. 



The 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 pliotographed 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 

 wave-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 iu 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 he 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 heen 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 witli 

 the quantity of substance in the flame, or with the length of time during which the plate was exposed. 



1. GOLB, 



2. Silver, 



3. Copper. 



4. Cadiiium, 



5. Zinc. 



6. Magnesium. 



7. Lithium, 



8. Thallium, 



9. Indium, . 



10. Gallium, 



11. Aluminium, . 



12. Arsenic, 



13. Meecuky, 



14. moltbdendm, 



15. Lanthanum. 



16. Iridium, 



17. Palladium, . 



PLATE XXIX. 



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. 



The flutings between wave-lengths 4000 and 3700 are not so well shown as in the 

 illustration to "Flame-Spectra," Part i., Phil. Trans., 1894. 



PLATE XXX. 



Detail not sufficiently strong to be reproduced with a distinctness equal to that 

 seen in the original photographs. 



From the nitrate. The sodium -lines have broadened out to a band. 

 PLATE XXXI. 



I The broadening out of the lines in these spectra is well seen, but faint bands hav( 

 not been reproduced in the engraving. 



Besides the fluted spectrum, there is a band of continuous rays caused by the white- 



PLATE XXXII. 



hot alumina. 



The continuous spectrum, and the bands beyond wave-leugtli 3000, are due to arsenic. 

 The lines seen are due to sodium, potassium, calcium, and iron. 

 From molybdenum trioxide. 



PLATE XXXIII. 



There are several bands composed of lines, and some lines independent of bauds, in 



this spectrum. 

 A number of strong lines accompany the bands in this .spectrum. 



