14 Barrett, Brown, & Haprienp—On the Magnetic and Electric 
desirable to submit the matter to more careful examination, and this we now 
proceed to describe. 
The chemical composition of the Swedish charcoal-iron S. C. I. has already 
been given, it contains 99:9 per cent. of iron and had a density of 7-84. 
- The aluminium-iron alloy, 1167 H, contains 97°3 per cent. of iron, 2:25 
per cent. of aluminium, and 0:24 per cent. of carbon, and had a density 
of 7:56. 
As was done in the case of the silicon-iron alloy, the specimen of aluminium- 
iron 1167 H, containing 24+ per cent. of aluminium, was turned down to a 
16000 
Fie. 5.—Permeability curves obtained from slender rods by the magnetometric method. 
slender rod 0°3914 cm. diameter, its length remaining as before, 102 cms., the 
length was therefore 260 diameters. The rod was then annealed in the same 
way, and simultaneously with the similarly turned rods of silicon-iron and 
Swedish charcoal-iron.* The heat treatment of the three rods being exactly 
similar, they were then compared magnetically by the magnetometric method, 
the same reflecting magnetometer being employed as before, and described above. 
The magnetising solenoid, 20 ems. longer than the rods, was fixed vertically 
70 cms. distant from the magnetometer. 
The relative permeability of the rods was first determined, and the results, 
* In the first instance the silicon-iron and pure iron rods were turned to 0:4 cm. diameter, but as the 
aluminium-iron when turned was found to be slightly smaller in diameter, the two former rods were now 
further reduced so as to make all three rods of exactly similar dimensions. 
