Kutherford. — On the Magnetization of Iron. 509 



detecting electro-magnetic radiation, and of investigating the 

 waves in free vibrating circuits. 



Before starting this research I was uncertain whether iron 

 was magnetic in very rapidly-oscillating fields or not. The 

 only information I could obtain on the subject is given in 

 the opening pages. What experimental evidence there was 

 seemed vague and contradictory. In this research, starting 

 from the magnetization of iron in ordinary leyden-jar dis- 

 charges, it has been shown that iron is magnetic for frequen- 

 cies up to 500,000,000 per second. On account of the small 

 quantities of electricity set in motion the experiments were 

 not pursued further, but I have no doubt that by the use of 

 very thin steel wires iron may be shown to be strongly mag- 

 netic for the highest frequencies yet obtained. If the mole- 

 cules of iron can follow the changes of magnetic force, which 

 is reversed 1,000,000,000 times per second, there can be very 

 little magnetic viscosity, and the molecules must move as 

 freely as when under the influence of an alternating current 

 of 100 per second. 



Iron has been shown to absorb energy and exhibit high 

 permeability in very rapidly varying fields ; the absorption 

 of energy has also been accurately measured. The resistance 

 of iron wires for leyden-jar discharges has been investigated, 

 and an approximate theory advanced to account for the effects 

 observed. In one case the resistance has been shown to be 

 120 times the resistance for steady currents. 



The division of currents in multiple circuits has been 

 investigated in several cases, and it has been shown that iron, 

 whether solid or finely divided, always increases the im- 

 pedance of a circuit. 



The use of magnetized steel needles as " detectors " and 

 "galvanometers" has been explained, and their possible use 

 also for measurement of the intensity of electro-magnetic 

 waves. 



Information with regard to the nature of the discharges 

 and the damping of vibrations has been obtained in the course 

 of the experiments. 



A more detailed though imperfect note is appended on the 

 " Eesistance of Spark-gaps," a subject on which little seems 

 to be at present known. 



Note on Eesistance of Spark-gaps. 



When a leyden-jar is discharged a bright flash of light is 

 the only apparent result of the energy stored up in the dielec- 

 tric of the jar. The energy of the discharge, however, has 

 been dissipated, due to several distinct causes. 



