82 Mr. R. H. M. Bosanquet on the Magnetic 
us most are those in the initial values of s and those in the 
coefficient of sin 6. We can only conclude, either that the 
iron is of very variable quality, or that the forging of the 
rings is liable to introduce these large discrepancies. 
I may mention here that, in accordance with Rowland’s 
direction, a coating of at least } of an inch was removed in 
the lathe from the rings after forging. The ring K was 
turned out of the very heart of a forged ring originally nearly 
four times its ultimate thickness. 
The Lowmoor iron ring shows low initial permeability and 
a high saturation-point. In both respects it much resembles 
ring F, but the maximum permeability of the Lowmoor is 
greater than that of I’, though considerably less than that of 
Hi or G; in fact the differences due to the type of iron appear 
inconsiderable compared with the differences between different 
rings of the same iron. 
The soft steel ring presents very remarkable results. First 
we notice that the saturation-point is decidedly high ; that is 
to say, by the employment of sufficient force, as shown by the 
low values of the permeability, the induction in the soft steel 
was actually raised to over 18,000. 
The initial permeability is about one third of the average 
value for soft iron; the maximum permeability about one 
fifth of the average value for soft iron. But the strangest 
thing of all is that the variable part of the permeability appears 
to be completely represented by a single term involving the 
sine of the angle proportional to the induction, so that the 
maximum permeability corresponds to an induction of about 
9000 instead of to an induction of between 5000 and 6000 
as is usual in soft iron. 
In the case of the hard steel ring the power employed was 
insufficient to force the steel up to its saturation-point, and 
before the ring could be re-examined with a larger number of 
windings the tubes of the boiler broke down and put a stop 
to work for the present. But the observations already obtained 
are very fairly represented by a formula which would give a 
high saturation-point. The initial permeability is less than 
one half that of the soft steel. The maximum permeability is 
about one third that of the soft steel, and it corresponds to a 
somewhat lower value of the induction than in soft iron, 
instead of to a higher value as in soft steel ; that is to say, 
what we may call the octave term (sin 20), which vanishes 
for the soft steel, has for the hard steel the largest proportional 
value that occurs in any of the ringsexamined. The physical 
meaning of this will be given us by my new theory. 
In Rowland’s paper above referred to he observes that it is 
