230 Mr. S. Bidwell. Effect of Magnetisation upon the [Mar. 1, 



length increased rapidly with the magnetising force, the maximum 

 increment which was obtained in a field (due to the coil) of about 

 140 units being as much as 45 ten-million ths of the length of the 

 wire. The same wire was then carefully annealed, and the experi- 

 ment repeated, with the results indicated in curve (2). It will be 

 seen that the maximum increment had fallen from 45 to about 8 ten- 

 millionths less than one-fifth of its former value and was reached 

 with a force of about 60 units. Finally, the wire was raised to a 

 bright red heat in a blowpipe flame, and dropped into cold water, its 

 subsequent performance being as indicated in curve (3). This last 

 operation was found to have raised the maximum elongation from 8 

 to 25 ten-millionths, while the corresponding magnetising force had 

 increased from 60 to about 110 units. 





Table I. 



