856 REPORT—1899). 
SATURDAY, SEPTEMBER 16. 
The following Paper was read ;— 
1. Erection of the New Alexander III. Bridge in Paris, 
By M. A. Ausy, of Paris. 
[Ordered to be printed in eatenso. | 
See Reports p, 469, 
MONDAY, SEPTEMBER 18. 
The following Papers were read :— 
1. Electrical Machinery on Board Ship. 
By A. Siemens, Jf Jnst.C.£. 
Lo 
On the Electric Conductivity and Magnetic Properties of an Extengive 
Series of Alloys of Iron, prepared by R. A. Haprieup. By Professor 
W. F. Barrett, /.2.8S., and W. Brown, B.Sc. 
During the last five years the authors have been engaged in the determination of 
the physical properties of upwards of 100 alloys of iron, many of them entirely 
new, and some of them presenting remarkable physical characteristics. This 
splendid series of alloys or ‘steels’ has been prepared at considerable expenditure 
by the liberality of Mr. Hadfield, M.I.C.E., Managing Director of the Hecla Steel 
Works, Sheffield, whose researches on the mechanical properties of many of these 
alloys are well known. Myr. Hadfield has also had a chemical analysis of the 
alloys made in the laboratcry attached to his works; the paper may therefore be 
said to be a joint contribution by three authors. 
The jirst part of the paper deals with the electric conductivity of these alloys. 
For the purposes of measurement the specimens were rolled into rods rather over 
a metre long and about half a centimetre diameter, and after their conductivity 
was measured in the unannealed condition they were then carefully annealed and 
re-determined. Annealing was found to increase the conductivity in the case of 
all the alloys. The potential method of measurement of conductivity was 
employed, a comparison being made with a standard rod of pure copper, of known 
conductivity, and also with a standard rod of the purest commercial iron, Full 
details of the method of measurement and the results obtained will be found in 
the forthcoming volume of the Transactions of the Royal Society of Dublin. 
In all the specimens the conductivity decreases as the percentage of the added 
element increases, at first rapidly and then very slowly. But the effect of 
different elements on the conductivity of the alloy varies largely. The addition of 
even small quantities of carbon, silicon, manganese, chromium, or aluminium 
lowers the conductivity of iron considerably, whereas corresponding quantities of 
nickel, copper, and tungsten have a much less effect. The conductivity of the 
aluminium steels is extremely low, a particular specimen having 5} per cent. of 
aluminium (with only 0:2 of carbon and the same amount of silicon) had a con- 
ductivity of only 2:16, pure copper being taken as 100, or a specific resistance of 
75 microhms per c.c., the specimen had also the low temperature coefficient of 
0:063 per cent. per degree Cent. It was a beautiful alloy and very ductile. But 
the highest resistance was found among the nickel manganese steels. Onespecimen 
having 25 per cent. of nickel and 5 per cent. of manganese with 1 per cent, of 
carbon, was found to have the extraordinary specific resistance of 97$ microhms 
per c.c. at 15° C, and a temperature coefficient of 0-085 per cent. per degree Cent. 
This alloy also was easily worked and drawn into wire, but was harder and less 
dyctile than the aluminium alloy just mentioned, 
he 
