266 Mr. H. Tomlinson on raising Iron under Temporary 



(1) The phenomenon is entirely absent in very well- 

 annealed iron wire which has not, after annealing, suffered 

 strain, nor is at the time under stress. 



(2) It is not sensible unless the temperature of the wire 

 has been previously raised to a bright red "*. 



(3) It becomes more and more sensible as the temperature 

 at which the sudden jerk occurs in the wire becomes lower 

 and lower, and is most pronounced in those wires in which 

 the jerk does not take place until the wire suddenly loses its 

 magnetic properties. 



(4) It is not sensible unless there is a sudden jerk ; the 

 jerk and recalescence occur at the same instant. 



Gore's phenomenon and the phenomenon of recalescence 

 do not occur in pure, or nearly pure, specimens of nickel or 

 cobalt; though, as is well known, nickel loses its magnetic 

 properties at a much lower temperature than iron, namely 

 from about 350° C. to 400° C. A most careful examination 

 of three different specimens of nickel wire, procured from 

 Messrs. Johnson and Matthey, was madej. Unfortunately 

 pure nickel wire cannot be drawn ; but two out of the three 

 specimens showed no trace whatever of the phenomena. The 

 third specimen showed very obvious signs of both phenomena; 

 but when tested was found, like iron, to lose its magnetic 

 properties at a dull red heat instead of at the lower tempera- 

 ture at which pure nickel loses its magnetic properties, and 

 therefore probably contained rather a large quantity of iron. 

 The other two specimens lost their magnetic properties at a 

 temperature of about 400° C. Only one specimen of cobalt 

 was examined. Cobalt has not been drawn into wire as yet, 

 though both Messrs. Johnson and Matthey, and Mr. W. 

 Wiggin, jun., have kindly attempted to do so for me. Mr. 

 Wiggin was, however, so good as to have rolled for me a spe- 

 cimen of cobalt, which is very nearly pure, in a strip about 

 J millim. thick, 12 millim. broad, and 60 centim. long. This 

 strip was tested with a Bunsen-burner and with a large 

 blowpipe, and showed no trace at any temperature of either 

 phenomenon when subjected to bending-stresses of various 

 amounts. Unlike nickel and iron, cobalt does not lose its 

 magnetic properties at any temperature at which it has been 

 tested. 



* This is not the case as regards the phenomenon of iron suddenly 

 losing its magnetic properties at a dull red heat. 



t Professor Barrett had previously shown the phenomenon to be absent 

 in nickel. 



