Determination of the Earth's Horizontal Magnetic Force. 379 



Table I gives the mean values of the various quantities specified for 

 the several groups ; while Table II gives the extreme values. 



Table I. — Mean Values. 

















10 5 x P/r 2 



at 30 cm. 





Num- 





















Group. 



ber in 



TT'K. 



m. 



I0 6 q. 



ioV- 





When +. 



When -. 





group. 

































Num- 



Mean 



Num- 



Mean 

















ber. 



value. 



ber. 



value. 





7 



3532 



921 



328 



]20 



6 "70 



4 



281 



3 



293 



13 



12 



2767 



672 



257 



119 



6*03 









9 



430 



C 



82 



2755 



873 



349 



144 



5-64 



40 



843 



3L 



354 



D 



12 



2657 



854 



302 



134 



6-43 



4 



918 



7 



290 



E 



10 



2520 



837 



349 



156 



7*56 



10 



655 









E 



7 



1667 



633 



350 



139 



371 



4 



545 









Totals 























and 



J 130 



2711 



840 



335 



140 



5 85 



62 



762 



50 



361 



means 























Table II. — Extreme Values. 

















1G 5 x P/r 2 at30cm. 





Group. 





m. 



10% 



loy. 



fX. 





















When + . 



When-. 







3741 



1142 



510 



185 



8-27 



374 



447 







3037 



653 



180 



23 



4-36 



64 



353 



B« 





3184 



799 



359 



224 



7-07 





688 







2334 



481 



211 



14 



5 31 





121 







3072 



1115 



764 



312 



6-88 



2529 



1488 



C< 





2483 



462 



167 



19 



4-19 



30 



10 







2825 



1197 



687 



261 



11 -89 



1775 



619 



D- 





2352 



505 



195 



51 



4 23 



520 



122 







2658 



906 



370 



332 



7-79 



11*8 





E- 





2422 



723 



321 



82 



7*02 



173 









1758 



111 



604 



339 



4-81 



693 





E 





1600 



451 



273 



35 



2 *57 



333 





Data were wanting for P in the case of eighteen out of the 130 collima- 

 tor magnets, and there were no data for K in the case of three magnets, 

 all of group C. In these twenty-one cases m was calculated from the 



