L. P. Wheeler — Dispersion of Metals. 



499 



by several investigators proceeding from the general hypotheses 

 of the electron theory. The formulae thus obtained for K 

 involve, however, too many undetermined constants to allow 

 of a satisfactory evaluation with the experimental data at our 

 command. Hence it seems best for the present purpose to 

 leave K indeterminate in the equations. The expressions 

 which have been obtained for a, on the other hand, contain but 



Table IV — Nickel. 



Observer 



1 



n 



nk 



^"Lao)- 12 



Xo ' 



r 



n 2 (/c 2 -l) 



A 



K 



Tool 



0-420/z 



1-42 



2 53 



48-3 



2-38 



4-40 



340 



29-6 



Bernoulli . 



•436 



1-74 



3-28 















Tool 



•460 



1-46 



2 75 



41-8 



2-21 



5 V 44 



349 



29-4 



Bernoulli . 



, -492 



1-74 



3-37 













Tool 



•500 



1-54 



2-98 



3~6 V 6 



2-ii 



647 



42-8 



363 



(< 



•540 



1-63 



320 



33-0 



1-98 



7-50 



46-7 



39-2 



Bernoulli . 



•546 



1-76 



3 44 

















u 



•578 



1-75 



3-48 



. _ _ 











Tool. 



•580 



1-73 



3-41 



30-2 



1-90 



8 V 62 



51-3 



42-7 



Drude - . . 



•589 



1-79 



3-32 













Bernoulli . 



•615 



1-85 



3-72 



. _ . . 













Tool 



•620 



1-82 



361 



27-6 



1-82 



9~-74 



560 



463 



Drude 



•680 



1-89 



3-56 









_ 





Tngersoll . 



•65 



1-91 



393 



27-4 



1-81 



11-8 



61-2 



49 4 



Tool 



•660 



1-95 



3-84 



26-0 



1-77 



110 



61-8 



50-8 



" 



•700 



2 03 



3-98 



23-5 



1-68 



11-7 



66-2 



54-5 



Ingersoll _ 



•87 



2-45 



4-80 



17-9 



1-48 



17-0 



88-0 



71-0 



a 



1-25 



2-92 



6-15 



922 



1-07 



293 



132- 



103- 



" 



1-75 



3-45 



7-76 



5-00 



0-79 



48-3 



188- 



140- 



" 



2-25 



3-95 



9 20 



319 



0-60 



69-2 



237- 



168- 



one undetermined constant and consequently can be profitably 

 used. 



The development of a in terms of the frequency of the cur- 

 rent is best accomplished by the method due to Lorentz, Jeans, 

 and H. A. Wilson. It seems preferable to that of Drude in 

 that the frictional term in the equation of motion of the free 

 electrons in the latter's method receives a more probable 

 physical interpretation in the more recent method. In this 

 method the equation of motion of the electrons is obtained 

 from a consideration of the loss of momentum (in the direction 

 of the acting electric force) sustained by a group of electrons 

 having velocities lying between v and v-\-dv. If we assume 

 that the electric force Is given by E=E £ _ipt , and that the 

 law of the distribution of the velocities among the groups is 

 that of Maxwell, we obtain from a consideration of the rate of 

 production of heat per unit volume 



