TRANSACTIONS OF SECTION G. 857 
The second part of the paper deals with the magnetic properties of the alloys ; 
complete B and Hf curves were made in the case of a large number of the speci- 
mens. The magnetometric method of measurement was employed, each specimen 
being taken through a magnetic cycle, with a maximum magnetising force of 
45 C.G.S. units. The induction, the retentivity and coercivity of each specimen 
are shown by the curves, and the permeability for a given magnetising force was 
estimated in each case. Mr. R. L. Wills, who, with Mr. R. G. Allen, assisted in the 
experiments, has also measured the areas enclosed by the curves, and thus deter- 
mined the energy dissipated per cycle in ergs per cubic cent. Some elements 
were found to affect the hysteresis very differently to others and to very different 
extents, depending upon the percentage of the element present. Annealing in 
the case of some of the nickel and of the chromium-nickel and chromium- 
manganese alloys converted a practically non-magnetic alloy into a strongly 
magnetic one. For magnetising forces up to about 8 COGS. units, the addition 
of 24 per cent. of aluminium actually increases the permeability of iron; very 
small percentages of nickel also have the same effect for lower magnetising forces. 
As the percentage of nickel increases, the induction and permeability rapidly 
decrease and the hysteresis increases, but between 243 and 314 per cent. of 
nickel in the alloy the hysteresis falls, owing to the rapid decrease in coercive 
force between these percentages. The 31 percent. nickel steel had in fact an 
exceptionally low coercive force, and a permeability greater than the best iron for 
very low magnetising forces. Mechanical tests, made by Mr. Hadfield, show a 
similar result, the curve representing the tensile strength of nickel steels rising 
rapidly from 7 to a 12 per cent. nickel steel, then remaining nearly stationary 
till 20 per cent. is reached, after which it falls rapidly to the highest per cent. 
nickel steel tried, viz. 314 per cent. This is exactly analogous to the curve 
representing the coercive force of nickel steels, These interesting results were 
obtained independently. Still more remarkable was the magnetic effect produced 
by silicon when alloyed with iron and steel; this is now under investigation. 
3. Some Recent Applications of Electro-Metallurgy to Mechanical Engineer- 
ing. By Suerarp Cowrer-Coues, Assoc.MInst.C.£., M1IM.L., 
MIELE. 
The author commenced by pointing out the prominent position electro-metal- 
lurgy is now taking in many workshops, and enumerated the uses to which electro- 
metallurgy is being applied. He then proceeded to give a description of an 
electro-galvanising plant as used for coating the tubes of water-tube boilers 
and the plates of torpedo-boat destroyers, and also gave details of the anode and 
cathode bars used for suspending the electrodes, and information as to the thick- 
ness of zinc applied and the current density and voltage employed. Estimates 
were given as to the cost and output of various-sized plants, and the advantages of 
electro-galvanising over hot galvanising were compared. The regenerative or 
recuperative process and methods of circulation were also described. 
Particulars were then given of various electro-chemical processes for cleaning 
iron and removing magnetic oxide and scale, and a model was shown of a mag- 
netic scale collector for collecting the scale from the acid solution after its removal 
from the iron or steel, so as to prevent the further unnecessary waste of acid. 
Experiments made in this direction tended to show that a considerable proportion 
of the acid is consumed by dissolving the scale after it has left the iron or steel. 
An electrolytic process for the manufacture of reflectors was then described, 
suitable for making parabolic reflectors for search-lights. The various steps of the 
process were given in detail. Briefly, the process consists in using a glass convex 
mould on which is chemically deposited a coating of metallic silver, and then 
polished so as to ensure the copper backing being adherent to the silver. The 
mould thus prepared is placed in a suitable ring and frame and immersed in an 
electrolyte of copper sulphate, the mould being rotated in a horizontal 
position, the number of revolutions being about fifteen per minute. The 
