672 Prof. Lynde P. Wheeler on the 



It remains to discuss equation (9) in the light of the 

 experiments. Since the values of r can now be regarded as 

 known (from equation (8)), it is obvious that this equation 

 gives us the means of ascertaining the values of K through- 

 out the spectrum. Further, it will be seen that the value of 

 K consists of two parts : that due to the term involving r, 

 and that due to n 2 (/c 2 — 1). The latter is the value of K to 

 be expected if no free electrons were present ; hence, we 

 may speak of the u dielectric " and the 4i conductor " parts 

 of K. In order to trace separately the influence of these 

 two parts, the values of each are given in the tables ; in 

 column 7 the values of ri\fc 2 — 1) as computed from columns 3 

 and 4, and in column 8 (headed A) the values of the 

 conductor term as calculated from the right-hand side of 

 equation (9). In column 9 is given the algebraic sum of the 

 two terms, or K ; which latter is also shown in the broken 

 line curves in the upper halves of the figures. 



It is obvious from these results, in the first place, that the 

 values of K are not zero— the value demanded by a perfect 

 conductor. In the second place, we observe that the presence 

 of free electrons (the conductor term) plays the pre- 

 ponderating role in the so-called dielectric constant, particu- 

 larly at the shorter wave-lengths. The dielectric term, 

 however, increases relatively to the conductor term with 

 increasing wave-length in all of the metals except cobalt. 

 Thus in silver the dielectric term increases tolerably 

 uniformly throughout the region covered by the measure- 

 ments from about 1 per cent, to about 60 per cent, of the 

 conductor term ; in copper from about 0*1 per cent, to 

 33 per cent. ; in gold from 1 per cent, to 27 per cent. ; in 

 nickel from 13 per cent, to 29 per cent ; while in cobalt the 

 proportion varies from 5 per cent, through a maximum of 

 about 17*5 per cent, (at the red end of the visible spectrum) 

 to about 6*5 per cent, at the extreme infra-red wave-length 

 measured. As in the case of equation (8), it is impossible to 

 predict from equation (9) the relative magnitudes of the two 

 parts for infinite wave-length, both because of the divergence 

 of $ 2 a ^ large values of X, and because of lack of knowledge 



the increase in r would be explicable. This hypothesis, however, even 

 more than the former, fails to elucidate the mechanism of absorption. 

 If it is adopted it would seem to be necessary to attribute the major 

 part of the absorption to the relatively fixed ious. Hence, further 

 assumptions as to the nature and connexions of these ions would he 

 necessary in order to explain the existence of the type of absorption 

 which experiment reveals. However, this is hardly the place in which 

 to follow further such speculations; the experimental basis is not 

 sufficient either in extent or precision. 



