Magnetic Permeability of various Alloys of Iron. 87 
curves show the resistances in the wnannealed condition. ‘The effect of annealing 
is to lower the curves in each case. Some of the irregularities observed, notably 
the loop in the manganese steels, are smoothed out by annealing, and the position 
of the copper steels would then be slightly below that of the tungsten steels 
instead of above, as shown in fig. 6. It must be borne in mind that (1) owing to 
small irregularities in the sectional area of the rods, and (2) the disturbing influence 
caused by small variations in the amounts of carbon, silicon, and manganese 
unavoidably present in the alloys, the curves here shown can only be regarded as 
an approximate representation of the effect produced by varying amounts of 
different elements on the conductivity of these alloys of iron. 
CLASS II. 
Effect of two Elements added to Ivon or Steel. 
We now come to specimens which exhibit the effect of two elements added to 
iron or steel; and for the sake of comparison with the last group, which shows 
the effect of copper on the conductivity of steel, we will first give a specimen of 
an iron alloy containing wckel as well as copper. The comparison is of interest, 
as the alloy has practically the same amount of copper and carbon as 1263 C in 
Group 8, only with 5:75 of nickel added to it. 
Group 9.-——NickEL-Coprer STExEt. 
Mark. Percentage Composition. | Conductivity Copper = 100. Raa 
Ni Cu C Unann. | Ann. Unann. | Ann. 
1252 B 5°75 Qo 0:18 4°3 4°5 40:0 38°2 
It will be noticed that the addition of the nickel reduces the conductivity of 
the alloy one-half compared with a similar copper steel without nickel. In like 
manner, the addition of copper to a nickel steel reduces the conductivity of the 
alloy when compared with a similar nickel steel without copper. This may be 
seen upon referring to the nickel steel curve in Plate II. or fig. 6. We will now 
take other double alloys of steel where nickel is one of the elements. 
Here is a group of alloys of nickel and chromium with iron, arranged in order 
of conductivity. Their conductivity, it will be noticed, is considerably lower 
than steels containing corresponding percentages of nickel alone. 
