268 Mr. H. A. Rowland on Magnetic Distribution. 



quite near one end, the zero-point being at 1 inch from the helix 

 toward the long end. Table III. is from a bar 2 feet long with 

 a helix 4 J inches long near one end, so that its centre was 19| 

 inches from the end on which the experiments were made, the 

 zero-point being at the end. 



In adapting the formula to apply to the case of Table I., 

 we may assume that at the end of the bar s = oo and C = 0, 

 which is equivalent to assuming that the number of lines of 

 induction which pass out at the end of the rod are too small 

 to be appreciated. 



Table I. 

 Bar *18 inch diameter. at end of bar. 



L. 



Q'e. 



Ob- 



Q'e. 



Calcu- 



Error of 



Q'e. 



Q'. 



Ob- 



Q'. 



Calcu- 



Error of 

 Q'. 





served. 



lated. 



served. 



lated. 







27 

 3-2 

 20 

 25 

 32 

 37 

 43 

 5-3 

 6-5 

 77 

 9-5 



















3 





•'•••• 



27 



35 



+ •8 



5 

 6 

 7 

 8 

 9 



10 

 11 

 12 

 13 

 14 



*2 : 

 2-4 

 2-8 

 3-5 

 4-3 

 5-2 

 6-5 

 8-0 

 9-9 



"o" 



- -4 



- -2 

 







+ •3 



+ •4 



59 

 79 

 10-4 

 13-6 

 17 3 

 21-6 

 26-9 

 334 

 411 

 50-6 



6-6 

 8*6 

 110 

 138 

 173 

 21-6 

 268 

 33-3 

 413 

 51*2 



+ 7 

 + 7 

 + •6 

 + •2 











+ •2 

 + •6 



( 



y =2-60( 6 ' 213L - e - 



•213L\ 











Q' e = r2-60(e' 213L +< 



-213L ) = 



•554( e - 213 



L._j_ 6 -*213] 



J ). 



In Table II. observations were not made over the whole length 

 of the rod, and the zero-point was not at the end of the bar. 

 It is evident, however, that by giving a proper value to s we 

 may suppose the bar to end at any point. As the rod is very 

 long, expressions of the form 



Q'_C" = C'e-' L -C" and Q' =rC'e-' L 



will apply. 



