Properties of an Extensive Series of Alloys of Iron. 5 
The last two of the above alloys 1411 and 1449 were found to have a lower 
intensity of magnetisation when annealed—?.e.when cooled slowly from whiteness— 
than when unannealed: but as was shown in our previous paper,* the effect of slow 
cooling on the alloy, marked 1411, is to render it harder to the file, and this 
again coincides with a worse magnetic condition: the behaviour of 1449 is referred 
to on the next page. 
This difference in hardness probably explains the remarkable magnetic effect 
produced by a high percentage of carbon in manganese steels or in nickel- 
manganese-steels. In our previous paper we pointed out that an excess of carbon in 
high manganese-steels softened them and increased their magnetic susceptibility. 
This fact comes out very strikingly in the foregoing tables. With low carbon a 19, 
or even 18, per cent. manganese-steel is practically non-magnetic, in all ordinary 
magnetic fields, but high carbon-steels, having the same percentage of manganese, 
can be slightly magnetised. Even in an 185 per cent. manganese-steel the 
presence of 14 per cent. of carbon enables a feeble magnetisation to be imparted. 
The same thing is observed in the nickel-manganese-steels. 
The importance of heat treatment, as affecting the magnetic character of steel, 
is well known, but it must be borne in mind (as stated above) that with certain 
steels, especially high manganese-stecls, the effect of slow cooling from a white 
heat is the reverse of that produced in ordinary steel; it softens the latter but 
hardens the former. Sudden quenching of a carbon-steel renders it hard and 
brittle, but causes a high manganese-steel or nickel-manganese-steel to become 
tough and to some extent soft. 
It is hardly necessary to point out the great commercial and_ practical 
importance of non-magnetic steels of considerable tensile strength, if their cost of 
production be not prohibitive, andif they can be machined without much difficulty. 
With regard to the latter point, the high manganese-steels which are non- 
magnetic, even when toughened by sudden quenching in water, are so 
intensely hard that they cannot be planed or turned, and hence can only be 
used rolled or in the form of castings. But several of the non-magnetic 
steels in Table I. are by no means so hard. These specimens can be planed 
or turned, and. are excellent homogeneous alloys, both from a metallurgical 
and mechanical point of view. ‘The least hard of these non-magnetic iron 
alloys was the one marked 13138, a nickel-manganese-steel; but others were 
also workable as judged by the file. 
Though it may not at present be commercially profitable to construct non- 
magnetic ships of one of these alloys, the increase of safety in navigation would 
be great if this could be done. There are, however, many purposes in electrical 
engineering, as well as in the construction of clocks and watches, where non-maguetic 
* Trans. Roy. Dub Soc., vol. vii., p. 97. 
