On Coefficients of Induction. 329 



towards condensation. That the silver haloids are similarly 

 affected by the same agencies. That a remarkable parallelism 

 is noticeable between the two actions, especially if we take 

 into account that in the haloids the influence of energy is to 

 some extent restrained by the strong affinity which the 

 halogens show for atomic silver. There is therefore reason- 

 able ground to suppose that in the silver haloids silver may 

 exist in the allotropic form. 

 Philadelphia, February 1891. 



XXXVII. On Coefficients of Induction. By A. ANDERSON, 

 M.A., Professor of Natural Philosophy in Queen s College, 

 Galway.* 



-j npHE following method of measuring the coefficient of 

 J- self-induction of a coil is somewhat similar to that of 

 Maxwell ('Electricity and Magnetism,' vol. ii. art. 778), in- 

 asmuch as a condenser is employed. But it is not a null 

 method ; and, although not absolutely necessary for rough 

 determinations, it is desirable to use a ballistic galvanometer 

 on account of the ease with which the throws of the needle 

 can be observed, and because less adjustments and observa- 

 tions have to be made. 



In fig. 1, E is the coil whose inductance is to be found. 



One pole of the condenser F is joined to D, and the other to 

 a mercury-cup r. G x and G 2 are mercury-cups forming the 



* Communicated by the Author. 



