Peirce. — Magnetization in Iron. 



Plate 1. 



Figure 3. A switch in the main circuit so arranged that if it be suddenly 

 thrown over, the energy in the medium wliich accompanied the old ciu-rent is 

 spent largely in heating an auxiliary coil. 



Jk 



Figure 4. The long period ballistic galvanometer. 



Proc, Amer. Acad. Arts and Sciences. — Vol, XLIX. 



