186 Proceedings of the Royal Society of Edinburgh. [Sess. 
X. — The Variation of Young’s Modulus under an Electric Current. 
By Henry Walker, M.A., D.Sc. ( Communicated by Professor J. G. 
MacGregor, F.R.S.) 
(MS. received May 16, 1910. Read June 6, 1910.) 
Part III. 
The results of the investigations on four metals, viz. steel, iron, copper, 
and platinum, form the subject of my two first papers. In Parts I. and II. 
the effects on the modulus when the wire was stretched with a small load, 
and also with a much greater load, were examined. In this, my third 
paper, the investigation of these metals has been extended in several 
directions. The scope of the whole work has also been widened by 
subjecting nickel and cobalt to examination. 
As the question of temperature still seemed doubtful, and as the 
justification given near the beginning of the second paper might not be 
altogether convincing, I thought it better to put the matter beyond all 
question. I therefore adopted the following method. Using the double- 
walled tube already described, the wires were passed through it and over 
the wheel in the same way as in the main experiments. The resistance 
of each wire was then determined at the temperature of the room, and at 
those of boiling sulphuric ether, ethyl-alcohol, amyl-alcohol, and steam. 
Also, at each of these temperatures each wire was subjected to the same 
loads as in the experiments in which the variations of the modulus were 
investigated. In all cases the difference between the resistance of the 
wire unstretched and stretched was small, even with the greatest load. 
In some cases the difference between the stretched and unstretched wire 
did not exceed what would have been produced by an increase in the 
temperature of 0*5° C. On the scale on which the curves are drawn, this 
difference in the temperature is inappreciable, so that there was no necessity 
to redraw the graphs in the two preceding papers. In this paper the 
temperature has been determined from the graph showing the resistance 
of the wire when subjected to the same load as in the experiment. 
The investigation of the behaviour of soft iron, steel, copper, and 
platinum has been continued by subjecting each wire to various loads 
intermediate to the two loads employed in the experiments described in the 
second paper. As stated there, it was found that when the load was 
considerably increased the modulus diminished uniformly in value, a 
