Mr. H. A. Rowland on Magnetic Distribution. 



269 



Table II. 

 Bar '39 inch diameter. at 1 inch from helix. 







1 

 2 

 3 

 4 

 5 

 6 

 7 

 8 

 9 

 10 

 11 

 12 

 13 

 14 

 15 

 16 

 17 

 18 

 19 

 21 

 23 

 25 

 27 

 29 

 31 



Q' e . 

 Ob- 

 served. 



717 



65-2 

 595 

 535 

 51-2 

 467 

 432 

 400 

 372 

 347 

 31-7 

 295 

 25-7 

 25-5 

 22-0 

 215 

 200 

 191 

 325 

 275 

 23 

 18-5 

 14-5 

 11-3 



Q'e. 



Calcu- 

 lated. 



70-8 

 65-3 

 60-2 

 55-5 

 51-2 

 472 

 43 5 

 40-1 

 370 

 341 

 31-4 

 28-9 

 266 

 246 

 22-7 

 209 

 193 

 178 

 31-5 

 267 

 22-8 

 19-4 

 16-5 

 14-0 



Error of 



Q'e- 



- -9 

 + -1 

 + 7 

 +2-0 





 + -5 

 + '3 

 4- 1 



- -2 



- -6 



- -3 



- -6 

 + -9 



- -9 

 + 7 



- -6 



- 7 

 -1-3 

 -1-0 



- -8 



- -2 

 + '9 

 +20 

 +27 



Q'-C" 



Ob- 

 served. 



825 2 



7535 



688-3 



628-8 



575-3 



5241 



4774 



434-2 



394-2 



3570 



322-3 



290-6 



261-1 



235-4 



209 9 



187-9 



166-4 



146-4 



1273 



94 8 



67-3 



44-3 



25-8 



113 







Q'-C" 

 Calcu- 

 lated. 



902-5 



825-9 



7551 



689-8 



629-5 



5743 



523- 1 



4760 



4325 



3925 



355-6 



321-5 



2901 



261-2 



234-5 



2100 



187-3 



166-4 



1471 



129-4 



97-8 



711 



48-6 



290 



12-6 



-1-2 



Error of 



Q'. 



+ 7 

 + 1-6 

 + 1-5 

 + 7 

 -10 

 -10 

 -14 

 -17 

 -17 

 -1-4 



- -9 



-r -1 



- -6 

 



+ '7 

 +2-1 

 +3-0 

 +3-8 

 + 4-3 

 +3-2 

 + 13 

 -12 



Q'-C" = 983 6 -' 08135L -80-5 = 983-(10)- ,0353L -80-5. 

 Q^=r983e-' 08135L AL=80-(10)-* 0353L AL. 



In Table II. the observations were near the. end of the rod, 

 and were repeated several times. Neglecting the end of the rod, 

 we have s= go . 



In these Tables we see quite a good agreement between theory 

 and observation ; but on more careful examination we observe a 

 certain law in the distribution of errors. Thus in Table I. the 

 errors of Q' are all positive between and 8 inches ; and this 

 has always been found to be the case at this part of the bar in 

 all my experiments. 



The explanation of this is very simple. In obtaining the 

 formulae, we assumed that the magnetic permeability of the bar 

 fx was a constant quantity; but it has been shown by Dr. 

 Stoletow and myself, independently of each other, that /.l in- 

 creases as the magnetism of the bar increases when the latter is 



