538 Mr. Warington on a lle'arrangemeni of the Molecules, SfC. 



communicates itself to the surface before the fixing and cool- 

 ing." The alteration in the internal arrangement of the par- 

 ticles, as proved by the surfaces of fracture, is not however 

 noticed, and the explanation is defective, as it supposes the 

 interior not to have assumed the solid state until the evolution 

 of the heat occurs. If such were the case it would be seen on 

 breaking it in the first instance. The phcenomena can only 

 be accounted for by admitting a certain degree of mobility 

 among the particles, and that a second molecular arrange- 

 ment takes place after the metal has solidified ; this may arise 

 from their not having assumed in the first state that direction 

 in which their cohesion was the strongest. 



That a very mai'ked and extraordinary alteration in the 

 characters and properties of various substances arises entirely 

 from this change in the position of their component particles, 

 effected either by the communication or abstraction of heat after 

 solidification, there can be no doubt. And these changes are 

 applied to many very important purposes in the arts and ma- 

 nufactures ; such as the hardening and tempering of steel, the 

 rolling of commercial zinc, and rendering that metal perma- 

 nently malleable, the annealing of glass, and a variety of other 

 uses, particularly in crystallization, which might be adduced. 



I'he following experiments were made to ascertain to what 

 extent the emission of latent heat takes place. The melted 

 alloy was poured in a perfectly fluid state on the bulb of a 

 thermometer placed in a small platinum crucible, having a 

 capacity equal to about "70 grain measures of water, and stand- 

 ing in a vessel of cold water or mercury. The thermometer 

 surrounded by the solidified metal and crucible was removed 

 from the cooling medium before it had reached its stationary 

 point, and the greatest decrease of temperature noted. The 

 heat then rose rapidly again, and the maximum effect was 

 registered. The fusing point of the alloy was 202° Fahr. 

 the following results were obtained: — 



