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22 On the Magnetic and Electric Properties of an Extensive Series of Alloys of Iron. 
when unannealed. By increasing the strength of the field the resistance to 
molecular change may be partially overcome, and the unannealed body thereby 
made more or less magnetic. The conversion of a magnetic into a non-magnetic 
body by alloying the former with certain metals may, therefore, largely depend 
upon the increase in mechanical hardness of the alloy. And conversely the 
increase in permeability which silicon and aluminium confer upon iron and steel 
is probably due to the greater mechanical as well as magnetic softness of 
the alloy. 
We desire to express our appreciation of the assistance Mr. 8. A. Edmonds, 
a Senior Student in the Physics Faculty of the College of Science for Ireland, has 
rendered us in some of the numerous observations and plotting of curves given in 
this part of our investigation. 
P.S.—Experiments are now in progress with a ring of the aluminium-iron alloy 
(only recently obtained) with which the cyclic curve and hysteresis loss can be 
more accurately determined.* The high permeability of this alloy would doubtless 
be still further increased by reducing the carbon it contains and by aslight altera- 
tion in the amount of aluminium present, and also by careful attention to the heat 
treatment of the alloy. 
* Note added later, June, 1902. The specimen of aluminium-iron of which the ring was made has not 
given at all such good results as the rod of this alloy which was first received, and with which the determina- 
tions given in the foregoing memoir were made. The permeability and hysteresis loss of the ring were found 
to be ¢nfertor to Swedish charcoal-iron. This may arise from some difference in heat treatment—which is 
now being tested—or more probably to a slight difference in the chemical composition of this specimen, 
arising from another casting, or to segregation occurring in some portion of the casting, or possibly to some 
other undiscovered cause. It is desirable to draw attention to this fluctuation in the magnetic character 
of the aluminium alloy, for—although no doubt at all remains in our mind of the accuracy of the 
comparative results given in the foregoing memoir, the experiments speak for themselves,—samples of 
aluminium with alloy may be placed on the market which may be found not to give the high magnetic 
quality we have proved to exist in the particular specimen we employed. A careful investigation is now 
being made with a view to the discovery of the cause of this anomaly. 
