ON THE MAGNETIC QUALITIES OF IRON. 
1021 
other, in a coil which had the same dimensions as the magnetizing coil of the 
first ring, but wliich was wound non-inductively. Hence, whatever heating effect the 
magnetizing current had on one ring, it also had on the other, though one ring only 
became magnetized. Both rings were subjected to precisely the same thermal 
influence, except that in the active ring the magnetism of the core was periodically 
reversed, and in the inactive ring a special heating current was used to balance the 
heat generated in the other by these magnetic reversals. The arrangements were in 
all cases such that the inactive ring could be made magnetically active and vice versd, 
without any change in the winding or structure of the rings, by merely changing the 
electrical connections of the divided coils which were wound in identical fashion on 
each. In those of the experiments that dealt with rings which had a core of 
insulated iron wire, the heating current was caused to pass through the wire of the 
core itself in the inactive ring—a particularly satisfactory arrangement, inasmuch as 
the heat generated by this current in the inactive ring was then distributed through¬ 
out the core in just the same way as the heat generated by magnetic reversals in the 
active ring. In experiments dealing with sheet metal cores a special coil was wound 
as close as possible to the core of the inactive ring to take the heating current. 
This method of measuring the heat due to magnetic hysteresis by securing a thermal 
balance between two rings, alike in all respects, was originally devised to give an 
answer to the question whether, when a transformer is in action, the heating of the 
core through magnetic hysteresis is the same when the transformer is “ loaded,” or 
when it is not; in other words, wBether the taking of current from the secondary coil 
has any inflnence on the amount of heat generated in the core, the limits of magne¬ 
tization and the frequency of the reversals being unaltered. Independent experiments 
by Professor Byan, Mr. Morley, and Professor Ayrton, on the efficiency of trans¬ 
formers, had apparently agreed on showing a marked reduction in the loss of energy 
due to magnetic reversals when the “ load ” was put on. Adding a secondary coil to 
each of our rings to make it into a transformer, we applied the above balance method 
to compare the rate of magnetic heating when the secondary was open with the rate 
when the secondary was closed through a low resistance, so as to apply a heavy 
“ load,” arrangements being at the same time used to keep the magnetic range and 
frequency unchanged. The result was that no change could be detected in the rate 
at which heat was produced by the reversal of magnetism when the “load” on the 
secondary coil was varied from nothing to an amount greatly in excess of any “ load ” 
used in practical transformers.* The conclusion being of this negative kind, a very 
short account of the experiments will suffice. 
The electrical connections are shown in fig. 24. On each ring of the pair a primary 
coil was wmund in two layers, and a secondary coil, also in two layers. In each coil 
* Since these experiments were made (and briefly published in ‘ The Electrician’ of Dec. 4, 1891), 
later tests of transformers, by Professor FLEiiiNa and others, have borne out our conclusion that the 
amount of “ load ” has no influence on the waste of energy through magnetic hysteresis 
