Properties of an Extensive Series of Alloys of Iron. 15 
when plotted, gave the B-H curves shown in fig. 5, where the abscisse are 
magnetising forces, and the ordinates the induction produced. 
It will be seen that, in a field of 10 units, the silicon-iron alloy crosses 
the Swedish charcoal-iron, whereas the aluminium-iron retains its pre-eminence 
up to the highest field here employed. The experiments were several times 
repeated with the same results, the rods being heated to whiteness and cooled 
between each experiment. In fig. 5 the sloping vertical axis indicates the 
correction for the demagnetising reaction of the ends, estimated for rods of 
260 diameters in length, according to Ewing’s experiments on iron wires.* 
That is to say, in estimating the induction B in any given field, the magnetising 
force H must be reckoned from the sloping, and not the vertical, axis. This 
has been done in the accompanying table, which gives the induction B, and 
permeability, », of these rods in fields up to 10 units, deduced from the 
curves shown on a reduced scale in fig. 5. 
TABLE IX. 
PERMEABILITY OF SrLicon-[Ron (898 E) anp Atuminium-Iron (1167 H) Attoys 
COMPARED witH Brest ANNEALED SwEDISH CHarcoal-Iron (S.C. I.), ann In THE 
FORM OF SLENDER RODS, LENGTH = 260 DIAMETERS. 
SI Gs Th 898 E. 1,167 H. 
H B o B. a B re 
| 
2 7,400 3,700 10,200 5,100 12,000 6,000 
4 11,150 2,790 12,300 3,075 13,800 3,450 
6 12,600 2,100 13,400 2,238 14,500 2,416 
8 13,600 1,700 13,800 1,725 14,900 1,862 
10 14,400 1,440 14,200 1,420 15,200 1,520 
The remarkable fact is here revealed that a permeability of 6000 is attained 
by the specimen 1167 H in a field of 2 units, But even this does not express 
the maximum permeability of the aluminium-iron alloy. In order to exhibit the 
permeability of this alloy, relatively to silicon-iron and Swedish charcoal-iron, the 
* The extreme magnetic softness of the aluminium-iron may require a greater correction than is here 
shown. It would be desirable to have some experiments on this point with various lengths of aluminium- 
iron wire, or long ellipsoids, compared with ring experiments. At present, however, the only specimen of 
aluminium-iron alloy we have to work with is the one slender rod. 
