1895.] Iron and Steel at Welding Temperatures. 351 



III. " Iron and Steel at Welding Temperatures." By THOMAS 

 WRIGHTSON, Memb. Inst. C.E. Communicated by Pro- 

 fessor ROBERTS- AUSTEN, C.B., F.R.S. Received Feb- 

 ruary 2, 1895. 



(Abstract.) 



The object of this paper is to demonstrate that the phenomenon of 

 welding in iron is identical with that of regelation in ice. 



The author recapitulates experiments made by him in 1879-80, 

 described in the proceedings of the Iron and Steel Institute for those 

 years. 



These experiments were upon cast iron, and proved the fact that 

 this form of iron possessed the property of expanding while passing 

 from the liquid to the plastic state during a small range of tempera- 

 ture, and then contracted to the solid state, and that the expansion 

 amounted to about 6 per cent, in volume. 



The experiments were carried out under two distinct methods, the 

 first being by the suspending of a cast-iron ball on a spiral spring, 

 and lowering the ball under the surface of a vessel filled with molten 

 iron of the same quality ; the change of volume was registered by 

 the contraction of the spring as the varying displacement of the ball 

 varied its buoyancy. 



The second method was by casting 15-in. spheres of cast iron, 

 and measuring the changing diameter as the sphere cooled, then 

 laying down on paper a curve of changing volume, which in general 

 character was found to be similar to the curves produced by the 

 instrument used in the first method. 



This property of iron resembles the similar property of water in 

 freezing, which, within a range of about 4 C., expands about 9 per 

 cent, of its liquid volume, and then contracts as the cooling proceeds. 



This property of water was investigated by Professor James 

 Thomson and by Lord Kelvin. The former showed that from 

 theoretical considerations there was reason to expect that in the case 

 of a body exhibiting the anomalous property of expanding when 

 cooled and contracting when heated, it should be cooled instead of 

 heated by pressure or impact. 



Lord Kelvin investigated the problem experimentally as affecting 

 freezing water, and completely demonstrated the truth of his brother's 

 reasoning. 



The experiments made by the author in 1879 and 1880 suggested 

 the view that this property of ice was connected with the property of 

 welding in iron, but this was only hypothetical, as the experiments 

 had been made on cast iron, which, probably on account of the 



