( cm ) 



))r(>li;il)ly lt(^ tjn( fjir \\ ronn, if \vc sii|i|(os(^ i( lo lie lielweeii oaiidfi; 



tliit< would iniplv llial at llie Ixtrdi'i- tlio iiidcx of alxsorption lies l»e- 



1 * 1 , 



tweeii — /■„ and /„. It tlieretbro n i-elates U) tlic hoi'dcr, the tor- 



10 37 



imda (29) shows that the limits for — are - {ii — »„) and -^ (?i — ??„). 



In Hallo's experiments the breadth of the Z)-lines was about 

 1 A. E. The relation between n and the wave-length 7. being 



2 jrc 



we find for that between small variations of the two quantities 



ictc , 



dn =: dX. 



Hence, if we put f/A = 0,5 A. E. = 0,5 X 10-« om., we find 

 1, — no — 0,26 X 10'2, 

 from which I infer that the value of t lies between 12 X lO-'^ and 

 24 X 10-12 sec. 



§ 10. In the case of carbonic dioxyd the number K may be 

 deduced from the measured intensity of absorption. In Angstrom's 

 experiments this amounted to 10,6 pCt. in a layer, 12 cm. thick, 

 and for X = 2,60 ft. The amplitude being diminished in the proportion 

 of 1 to ^-''o- in a layer whose thickness is :, and the intensity of 

 the rays being proportional to the square of the amplitude, we have 



e-^*l'o = 0,894, 

 and 



ko = 0,0046. 



Now, by the formulae (27), (12), (10) and (18) 

 _iVe'T 



4cm 



^ 4 c m ko 



Here r and /„ are known by what precedes. As to the charge 6, 

 it is, in all probability, equal to that of an electrolytic ion of hydrogen. 

 It is therefore expressed in the usual electromagnetic units by 

 the num.ber 1,3 X lO^^o^ and in the usual electrostatic units by 

 3,9 X 10—"*. The unit of electricity used in our formulae being 

 1^4 31 = 3,5 times smaller than the common electrostatic one, we 

 must put 



e = 14 X 10-1" (30) 



