1905-6.] Electric Oscillations and Magnetic Properties of Iron. 43 
The curves show the results fully. The effects of superposing 
oscillations, as nearly as possible uniform in intensity and 
frequency, at approximately equidistant points all round the cycle, 
are as follows first, the area enclosed is enormously increased 
in comparison with the normal hysteresis loop ; second, it is also 
greater than the hysteresis loop obtained when the oscillations are 
permanently acting (this is in accordance with what has been 
stated under “ Retentivity ” ) ; and third, the amount of instan- 
taneous induction change which occurs upon the superposition of 
oscillations depends entirely at what particular point of the cyclic 
field they are superposed. 
But the above conditions are not those of practical telegraphic 
work. If signals are to he received, the waves must be transmitted 
more or less irregularly. 
Tig. 7 shows what takes place when oscillations are superposed 
and withdrawn somewhat irregularly at various points during two 
complete cycles. The results are obvious. The induction changes 
now caused by the superposition of oscillations are determined 
not only by the particular point at which they are superposed, but 
by previous irregularities. Thus, if the irregularity be a pause in 
the signalling, the effect of succeeding signals may either be 
increased or decreased. If signals are not received when their 
effect is a maximum, the effect of succeeding signals may be 
decreased ; on the other hand, if they are not received when their 
effect is a minimum, the effect of succeeding signals may be 
greatly increased. Note, also, the limitation of the total induction 
change per cycle or half cycle to which the irregular receipt of 
wave signals may give rise. 
Marconi’s first form of magnetic detector appears to owe its 
sensitiveness to the fact that the instantaneous induction change 
which takes place when electric waves are superposed at many 
points of the field cycle is great ; but it is equally certain that it 
owes its imperfections to the fact that the field is varying, signals 
not being superposed at one definite point of the cycle. 
The function of the moving field, therefore, is not to increase 
the sensitiveness of the iron ; it merely renders the receipt of 
signals possible, by removing the iron from that particular cyclic 
position at which the immediately preceding signal was received, 
