438 Mr. R. S. Willows on the Variation of t/ie 



another cycle gave a curve parallel but not coincident with 

 B. From the shape of the two curves it seems very probable 

 that they should coincide above 40° instead of being merely 

 parallel. In amalgams containing more than 10 per cent, of 

 zinc this coincidence above a certain temperature does actually 

 take place. A probable explanation is as follows : — In the 

 case of the lower percentages of zinc the amalgam consists of 

 an intensely crystalline mass surrounded by a fluid containing 

 less zinc. In the case of the next amalgam tested, containing 

 9"5 per cent, zinc, the amount of this fluid was very small 

 indeed, while for the higher percentages of zinc none was 

 present as far as could be seen. When the temperature is 

 raised, those containing small amounts of zinc ha\ r e their 

 crystalline structure greatly modified or entirely destroyed. 

 On being cooled, the structure they assume is slightly 

 different from that they possessed originally, and the re- 

 sistance is altered accordingly, while on again being heated 

 the modifications they undergo are nearly of the same order 

 as in the first case, thus giving a parallel curve. 



Several different spirals were filled with amalgam having 

 this composition with the same results. Those which contain 

 more zinc than 10 per cent, have curves which differ greatly 

 from those given in fig. 1, and along certain parts the two 

 curves obtained from the same amalgam coincide, probably 

 because, the melting-points being higher, the crystalline 

 structure is not so greatly altered. 



Fig. 2. — Resistance of an Amalgam containing 9-5 per cent, of Zinc. 



Fig. 2 represents the results for an amalgam containing 

 9*5 per cent. zinc. As in the previous case A was obtained 

 directly after the spiral had been heated several times, while 

 curve B represents the results of measurements made after 

 allowing the spiral to stand lor some weeks at the temperature 

 of the room. 



