E 
JL] 
VIL. 
AN INVESTIGATION OF THE CONNEXION BETWEEN BAND AND LINE 
SPECTRA OF THE SAME METALLIC ELEMENTS. 
By WALTER NOEL HARTLEY, D.Sc. F.BS., 
Royal College of Science, Dublin. 
IRGATES leur 
[Read, June 16; Received for Publication, Junr 19; Published, Ocrozrr 1, 1908. } 
PART Tf. 
INTRODUCTION. 
In three papers, published in the years 1882-83,* the connexion between the 
atomic weights, the chemical properties, and the spectra of the elements was 
pointed out, and the law of constant differences was demonstrated in the intervals 
between the lines in the spark spectra of magnesium, zinc, cadmium, also copper 
and silver. In conformity with the periodic law it was found that the line 
spectra of different groups of elements were spectra similarly constituted, from 
which it was deduced that they are produced from similarly constituted molecules 
containing the same kind of matter in different states of condensation. As only 
monatomic molecules were under consideration, it was believed that the atoms 
were composed of parts, and that as more of these definite parts were contained 
in one volume of the vapour, the mass of the atom increased by a definite 
quantity, and in any well-defined homologous group the elements possessed 
gradational differences in properties. 
In another series of paperst the nature and constitution of various flame- 
spectra were examined, and it was shown that many metals have two distinct 
* Jour. Chem. Soc., ‘‘ Note on certain Photographs of the Ultra-violet Spectra,” &c., 41, 84, 1882; ‘«On 
Homologous Spectra,” 41, 390, 1883; ‘‘On the Spectrum of Beryllium,” &c., 42, 316, 1883. 
+ ‘“‘Flame-Spectra at High Temperatures,” Phil. Trans., 1894, 185, part I, pp. 161-212; Parts IT. 
and IIT., pp. 1029-1091 ; and 1901, 196, pp. 479-506; also Hartley and Ramage, Sci. Trans. Roy. 
Dublin Soc., 1901; 7 Series, pp. 389-352. 
TRANS. ROY. DUB. SOC., VOL. IX., PART VII. Q 
