294 MAGNETISM 



N turns on the jar-primary and N' turns in the secondary round it, 

 and if the area of cn>- Action of the primary is A and it* length 

 M. the mutual induction of primary and sccondan 



If the jar is now filled with liquid of susceptibility *-, and if 

 we suppose its cross-section to be A also, the mutual induction is 

 altered to 



or increased hy 



The balance between the pair of secondaries will therefore be 

 destroyed, and a current \vill flow through the gal 



To measure Ihis increase in mutual indu. ; lir of 



coils was arranged, one in the prii d the c the 



secondary circuit, so that the mutual induction, ai i dl, 



might IK- \aricd from h .lount mca-i 



dimensions and positions ,,f tin coiN. This third mutual induction 

 MM 10 arranged that it exactly neutralised the current di:> 

 the insertion of the liijiiid, and so the \alue of the nurease 

 47r/f.47rNN / A/2/ was known, and K was determinate. '1 

 showed that Foucault currents in tin- jar c<>uld not have an 

 appreciable effect. 



The value of 10** for water was found to be 0'77, agreeing 

 closely with Curie's value - The su M cptibilr salt 



solution iu water arises partly from the water and partly t 

 the salt, so that, if * is the s,,sceptibilit v of the sohr 

 K + 0-77 X 10-* is that of the salt alone I : old iron 



salts this was found to depend only on the weight of iron in tin- 

 salt and not on the nature of the acid radicle, U-ing proportional 

 to the weight of iron NY per c.c. of solution, thoi 

 for eijual weights in tin I and ii .-trie salts. The 



values obtained for t em }>eratures about 1" re: 



10* 



Fe.C'e - 



Fed, aoc\\ 



The values obtained for the dry salts were approximatel 

 same. 



All the salts showed a fall in *, with rise of temperature of the 



order of i per cent, per degree C. 



