TRANSACTIONS OF SECTION A. 903 
I have also experimented on hydrogen and oxygen gases in this apparatus in a 
way precisely similar to that described above. The chamber was very carefully 
exhausted, and the Volta contact effect tested with the electrometer. Hydrogen 
was then admitted, and while it was entering, which it was forced to do slowly, 
the electrical testing was repeated several times. 
A second and a third exhaustion were made, and hydrogen admitted a second 
and a third time. 
The same was subsequently done with oxygen, except that it was, of course, 
sufficient to admit the oxygen a single time. The result of my investigation, so 
far as it has gone, is that the Volta contact effect, so long as the plates are clean, 
is exactly the same in common air, in a high vacuum, in hydrogen at small and 
great pressure, and in oxygen. My apparatus, and the method of working during 
these experiments, was so sensitive that I should certainly have detected a varia- 
tion of 1 per cent. in the value of the Volta contact effect, if such a variation 
had presented itself. To do away with all question as to the dependence of the 
Volta effect on ‘ancient air sheets,’ I propose to modify my apparatus by making 
the vacuum chamber much longer, and finally of combustion tubing. I shall then 
apply great heat to the plates while they are contained in a vacuum as high as I 
cancommand, If then there be any ancient air-sheets existing, they must either 
be driven off or else absorbed into the plates. If any gas be driven off, it will be 
removed by the pump. The plates will then be tested when they have perfectly 
cooled, and the value of the contact difference determined. That being done, the 
atmosphere air or some other gas will be admitted, and the contact difference will 
be again determined. The effect of the presence of the atmosphere or other gas 
will, I think we may safely suppose, be thus ascertained. 
In conclusion, I have to express my indebtedness to Mr. J. Rennie, assistant to 
the Professor of Natural Philosophy in the University of Glasgow, for most 
valuable aid during my investigation. 
10. On a Specimen of almost Unmagnetisable Steel. 
By J. T. Borromisy, M.A., F.R.S.£. 
The author has examined a specimen of steel presented to Sir William Thomson 
by Mr. R. R. Eadon, of the firm of Moses Eadon & Sons, Sheffield. This steel is 
made under Hadfield’s patent, and contains 15 per cent. of manganese, and one 
side of the specimen bar has been polished, and shows that the steel is capable of 
taking a very high finish. The present specimen has probably a tensile strength of 
forty-five tonsto the square inch. To test it magnetically, the bar was first touched 
with steel magnets, and such preliminary trials seemed to show that the magnets 
had not the slightest effect upon it. It was then placed between the poles of a 
powerful Rhumkorf electro-magnet, which was excited by forty large tray 
Daniells, arranged in fours for quantity and ten in series; and the process for 
magnetising which is always used in the Glasgow University laboratory, and 
which is very satisfactory, was proceeded with. It was very astonishing to find 
the bar of steel absolutely unaffected by the electro-magnet, so far as could be 
perceived by the hand. 
After magnetisation the bar was carefully tested by the magnetometer method, 
a mirror magnetometer being used for the purpose. The weight of the bar is 
192:09 grammes, its length is 14:29 centims, it is of square section, and is 1°5 
centim thick. ‘The effective length of the bar as a magnet was estimated at 10 
centims, The magnetometer determination gave for the magnetic moment 
p= 2°55 ©.g.8. 
Dividing by the weight of the bar we find for the magnetisation per gramme of 
this specimen of steel, 0°013 c.g.s. 
To compare this with other specimens of steel we find in many specimens that 
magnetisation of 40, 50, or even 60 c.g.s. per gramme can be obtained. In some 
specimens as much as 90 or even 100 c.g.s. per gramme has been obtained. 
. P.S. The author has been informed that Dr. Hopkinson has already experi- 
