250 Proceedings of the Royal Society of Edinburgh. [Sess. 
magnetic and non- magnetic metals exhibit marked hysteresis, which 
diminishes in amount as the load is increased, and which ultimately 
vanishes. Again, as the load is gradually increased, the maximum value 
is reached in continually diminishing fields; and when the field is kept 
constant and the load varied, the maximum value is reached with continually 
diminishing load. Thus we are led to the two important and fundamental 
facts brought out by the experiments as a whole — first, when rise of 
temperature is produced by an electric current combined with moderate 
longitudinal stress, that there are irreversible variations of Young’s 
Modulus in both magnetic and non-magnetic metals ; and second, that 
the curves exhibiting these variations display a marked similarity in both. 
Finally, I desire to place on record my great indebtedness to Professor 
MacGregor for the loan of books, for access to the libraries of the University 
and the Royal Society, for references to the literature of the subject, and 
also for providing me with two strips of cobalt, as I had found it impossible 
to obtain rods of a size suitable for these experiments. I desire also to 
thank Professor Knott, Professor Peddie, and Mr. James Russell, Edinburgh, 
for many helpful suggestions and advice readily and kindly given at all times. 
( Issued separately , January 13, 1911.) 
