PROPAGATION OF MAGNETIZATION OF TRON. 113 
In fig. 20a we have plotted the amperes per sq. centim. at the different radii, and for 
the several epochs, and in each case, by drawing a curve fairly through these points, 
as shown in the figure, we are able to produce areas in fair correspondence with the 
areas obtained by means of the given cyclic curve. The comparative areas are given 
in Table VII. 
The results shown in fig. 22 are by no means so satisfactory as the results given by 
other figures, but we have thought it better to insert them here, as we do not wish 
to make any selection of results which might give an idea of average accuracy greater 
than these experiments are entitled to. 
Referring now to the summary of results in Table V., we note the marked effect of 
change of frequency upon the average induction per unit area of the innermost coil 
No. 1, when dealing with comparatively small maximum inductions. Compare the 
results given in figs. 19 and 20. The maximum force per centim. linear due to the 
current in the copper coils is 4°8 in each case, but the average induction per 
sq. centim. of coil No. 1 is reduced from 7690 to 1630 by a change of frequency from 
go to 35. Thisis, of course, not the case on the higher portion of the induction curve, 
as is shown by the results of figs. 21 and 22, although the resultant force H is 
reduced by the induced currents. 
In fig. 23 the maximum amperes in the copper coils is ‘24, and the periodic time is 
reduced to 4. An inspection of these curves shows the marked effect of change of 
frequency, coil No. 2 being exceedingly diminished in amplitude as compared with 
No. 3. 
Asan example of the practical bearing of this portion of the paper, suppose we 
have a transformer core made out of iron wire, 1 millim. in diameter, the wires 
being perfectly insulated from one another. The outside diameter of our outer tube 
: rs (oushs : 3 6 be Ne 
is 101°6 millims. Similar events will therefore happen at times, varying as Gia) : 
Take the case of fig, 19, in which the periodic time is 80 seconds, and the maximum 
average induction per sq. centim. is about 7000. 
(101-6)? 
a 
practice. The ergs dissipated per cycle per cub. centim. are 3820 by induced currents, 
and about 3000 by magnetic hysteresis. We see further, from fig. 20, that at 500 
periods per second only the outside layers of our 1 millim. wire are really useful. 
= 129 periods per second, and this is an example which might arise in 
As another example, take the case of an armature core of a dynamo electric 
machine in which a frequency of 1000 complete periods per minute might be taken. 
In fig. 21 the periodic time is 80, and the maximum average induction per 
sq. centim. is 15,000. 
We have 
sy = SO) (o/ LOS) 
8 
I 
e 
i=) 
— 
S 
eo 
36 = nearly 3 millims. 
MDCCCXCV.—A. Q 
