the Directive Power of Magnets, fyc. 



227 



Total force acting on the small magnet at each station. 









Large 



Large 



Galvanic 



Galvanic 





No. of Station. 





magnet 



magnet 



coil with 



coil without 









presenting 



presenting 



iron core. 



core. 









its edge. 



its flat side. 







1 



16 





274 



250 



310 



216 



2 



15 



17 



30 



326 



293 



330 



240 



3 



14 



18 



29 



408 



363 



413 



333 



4 



13 



19 



28 



566 



480 



515 



550 



5 



12 



20 



27 



678 



542 



634 



1000 



6 



11 



21 



26 



622 



480 



585 



1470 



7 



10 



22 



25 



513 



454 



565 



1925 



8 



9 



23 



24 



600 



584 



840 



2700 



31 



50 





160 



160 



164 



184 



32 



49 



51 



68 



163 



165 



180 



192 



33 



48 



52 



67 



191 



183 



195 



225 



34 



47 



53 



66 



224 



200 



221 



305 



35 



46 



54 



65 



235 



217 



227 



400 



36 



45 



55 



64 



211 



197 



215 



427 



37 



44 



56 



63 



193 



180 



200 



44 4 



38 



43 



57 



62 



175 



173 



195 



485 



39 



42 



58 



61 



181 



177 



208 



583 



40 



41 



59 



60 



201 



193 



227 



690 



2. When the flat side is presented to the small magnets, the 

 same statement holds for the outer circuit, but not for the inner 

 circuit, 



3. With increase of distance, the diminution of force is much 

 more rapid at the end than at the side of the large magnet. 



4. The law of effect of a soft-iron bar surrounded by a 

 galvanic coil differs, but not greatly, from that of the large 

 magnet presenting its edge. It would seem not improbable 

 that this may depend partly on the effect of the coil which 

 encloses the iron bar ; and if so, the law for a soft-iron bar 

 approaches still more to that of a magnet. 



5. The exhibition of the effect of the magnetic coil alone is 

 worthy of careful examination. The first thing which will 

 strike the eye is the astounding increase of power produced by 

 the insertion of the soft-iron core. At the sides of the magnet, 

 where the measures of force for the coil alone are 1*5 and 1*8, 

 those for the coil with core enclosed are 164*0 and 310*0; at 

 the ends, where the coil alone gives 5*75 and 22*5, the coil with 

 core included gives 227*0 and 840*0. 



6. The law of magnitude of forces for the coil alone differs 

 greatly from that of a steel magnet. In the inner circuit the 

 proportion of the force at the end to force at the middle of 

 length is, for the steel magnet 4yf> for the coil -Wr - ? in the 

 outer circuit they are -fg-5- and -f-f-f-. 



7. Still more remarkable is the difference in the law of 



K 2 



