Determination of e, N, and Related Constants. 13' 



above value of b taken in connexion with each individual set 



of values of the observed quantities — and e%i. It will be 



n pa 



seen that the final mean value of e* obtained by this method 



of analysis — a method which yields the most reliable value 



of e% obtainable from the data at hand — is 



ei = 61-126 xlO" 8 . 



There is but one drop in the table which yields a value of e* 

 differing from this by as much as one-third of one per cent., arid' 

 the probable error of the mean computed by least squares is one 

 part in 4000. 



No such precision, however, is claimed for this deter- 

 mination of el. It is '07 per cent, higher than the value 

 (61-086) which I published in 1913, both values being 

 computed in terms of '0001824, as the value of the co- 

 efficient of viscosity of air. Dr. Harrington's new value 

 of this constant, viz. '00018227, is, however, more reliable 

 than the old one and is '07 per cent, lower than that ; so 

 that the new value of e and N computed solely from the new 

 data obtained in this redetermination is exactly the same as the 

 value published in 1913. The maximum uncertainty in this 

 value was then estimated as one part in five hundred. This 

 work has reduced it so that that it is no more, I think, than 

 one part in a thousand ; for it now contains but two factors 

 which are uncertain by as much as one part in two thousand, 

 namely, the coefficient of viscosity of air and the cross-hair 

 distance. The exactness of the agreement to four places 

 with the 1913 value is, of course, accidental. This is,, 

 however, the third time that with independent deter- 

 minations (one unpublished) I have come out well within 

 one-tenth per cent, of the foregoing result. 



The result of this investigation may, then, be stated as 

 follows : — 



e = 4-774 xlO" 10 , ±'005, 



N= 6-062 xlO 23 , ±-006, 



the last number being obtained from 



N x 4-774 x 10" 10 = 9649-4 x 2-9990 x 10 10 . 



Since this is an attempt at a precise determination, and 

 by far the most carefully carried out of any work which 

 I have thus far done upon the evaluation of the electron, it, 

 is perhaps worth while to give more of the original data 

 than would otherwise be justified, in order that others may 

 better form their own estimates of its probable reliability.. 



