582 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



kilograms of very soft, varnished iron wire, about one tenth of a milli- 

 meter in diameter. The curves OHD, PDXU were taken when the 



Y 



TIME. R 



FiGUKE 38. ODHQ represents the curve of growth of a current in the 

 exciting coil of the toroid DN, if the circuit was suddenly closed when its 

 resistance was r. If the circuit was first closed with a higher resistance {r+s), 

 which corresponded to a steady current of intensity OT, and if the resistance 

 s was suddenly shunted out, the current rose to the intensity OP in the man- 

 ner indicated by the curve EZQ, which, as Figure A shows, is of exactly the 

 same form as the upper portion of ODHQ. 



cores had been thoroughly demagnetized just before the experiment; 

 the curves MNC, QCZB after the core had been put a number of times 



TIME. 



Figure 39. 



through the cycle corresponding to the excitation used. The toroids 

 were in simple circuit with a storage battery, an oscillograph, and a 



