( 438 ) 
D, are most readily interpreted by considering them as originating 
from a triplet and not from-a sextet. 
It seems rather superfluous to give any further explanation of 
figs. 8, 4, 5; in the case relating to fig. 5, the vapour density is 
again greater than in fig. 4. All the phenomena we have considered 
are qualitatively in excellent accordance with Vorer’s theory. 
The phenomena described for D, and PD, again demonstrate the 
existence of very characteristic differences between different spectral 
lines, differences no less striking here than in the case of the related 
phenomena of the magnetic separation of the spectral lines and of 
the rotation of the plane of polarization in the interior‘) of, and 
close to, the absorption line. It is certainly very interesting that the 
theory explains the entirely different behaviour of D, and D, in the 
case now considered by differences between the velocities of propa- 
gation of vibrations normal and parallel to the field, assuming, of 
course, the magnetic division of the lines. 
Physics. — “The motion of electrons in metallic bodies’. 1. By 
Prof. H. A. Lorenrz. 
It has been shown by Rigcke*), Drupr*) and J. J. THomson ‘*) 
that the conductivity of metals for electricity and heat, the thermo- 
electric currents, the THomson-effect, the Harr-effeet and phenomena 
connected with these may be explained on the hypothesis that a 
metal contains a very large number of free electrons and that these 
particles, taking part in the heat-motion of the body, move to and 
fro with a speed depending on the temperature. In this paper the 
problems to which we are led in theories on these subjects will be 
treated in a way somewhat different from the methods that have 
been used by the above physicists. . 
§ 1. I shall begin by assuming that the metal contains but one 
1) Zeeman, Proc. Acad. Amsterdam May 1902, see also the description of another 
phenomenon in Vorer, Göttinger Nachrichten, Heft 5, 1902. 
2) E. Riecxe, Zur Theorie des Galvanismus und der Wärme, Ann. Phys. Chem. 
66 (1898), p. 353, 545, 1199; Ueber das Verhältnis der Leitfiihigkeiten der Metalle 
für Wärme und für Elektrizität, Ann. Phys. 2 (1900), p. 835. 
3) P. Drupe, Zur Elektronentheorie der Metalle, Ann. Phys. 1 (1900), p. 566; 
3 (1900), p. 369. 
4) J. J. Tuomson, Indications relatives à la constitution de la matière fournies 
par les recherches récentes sur le passage de |’électricilé à travers les gaz, Rapports 
du Congrès de physique de 1900, Paris, 3, p. 138 
