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ME. H. WILDE’S EXPERIMENTAL RESEARCHES 
itself in the electro-helices, with a decreasing intensity, simultaneously with the decreasing 
flux of magnetism in the iron itself. 
50. It is this important retentive property of the electro-magnet which maintains its 
attractive force unimpaired, notwithstanding the intermittent character of the electricity 
transmitted through the electro-helices ; for, as is well known, no current whatever is 
produced from the armature of the magneto-electric machine when in certain positions 
during its revolution. These positions correspond, in some measure, with the dead 
points of the crank of a steam-engine, the fly-wheel of which performs the same function 
dynamically , as that which the electro-magnet performs statically, in the case of the 
magneto-electric machine. 
51. That the charge retained by the electro-magnet is, as has already been observed, 
much more powerful than that which the magneto-electric machine is of itself capable 
of producing, is evident from the severe shock which is felt when the body forms part 
of the circuit, and also from the more voluminous spark which appears at the point of 
disjunction of the wires when contact with the machine is broken. 
52. That this increase of electric force in the electro-magnet is the consequence or 
effect of a certain number of electrical waves transmitted through the electro-helices, and 
succeeding each other with sufficient rapidity to sustain the increasing flux of magnetism 
in the iron, is manifest from the time which elapses before the electricity transmitted 
through the helices attains a permanent degree of intensity, and before the electro- 
magnet acquires its greatest amount of magnetism (45)*. 
53. That the length of time which was observed to elapse, and the number of waves 
which required to be transmitted through the electro-helices before the current from the 
magneto-electric machine attained a permanent degree of intensity, and the electro- 
magnet acquired its greatest amount of magnetism, are dependent upon the magnitude 
of the waves of electricity transmitted through the electro-helices, is evident from the 
fact that the same degree of intensity of the current (as measured by the balance), and 
the same amount of magnetism in the electro-magnet, were obtained with a much 
smaller number of waves, and in a shorter time, from a large electromotor, than could 
be obtained with a much greater number of waves from a small electromotor (46). 
These observations will be further confirmed by experiments to be hereafter adduced. 
54. The cause of the great difference between the attractive force of a permanent 
magnet and that of an electro-magnet excited through its agency, and also the agreement 
of the phenomena with the principle of the conservation of force, now become sufficiently 
manifest to render it unnecessary, at the present time, to institute a more rigorous com- 
parison between the quantities of magnetism and electricity of the magneto-electric 
machine, and the quantities of the same forces developed in the electro-magnets (23, 33). 
The general conclusion which may, however, be drawn from a consideration of the pre- 
ceding experiments is, that when an electro-magnet is excited through the agency of a 
permanent magnet, the large amount of magnetism manifested in the electro-magnet, 
* Philosophical Transactions, 1846, p. 6. 
