436 Mr. H. F. Newall on Peculiarities observed 



incline to regard the change going on in iron and steel at 

 high temperatures as partaking of the nature of an explosion, 

 in that once started it continues throughout the mass of the 

 iron, and is evidenced amongst other phenomena by the reglow. 

 Until the " darkening " has taken place the iron is not in a 

 state fit to explode, so to speak ; and hence it is necessary to 

 raise the iron above this temperature in order that reglow 

 may be possible. But before the iron can be raised above 

 this temperature, heat must have passed into it in sufficient 

 quantity to separate the elements producing the explosion. 

 My evidence for this view of the matter I hope to publish 

 in full. 



Briefly, I have shown that reglow is not due to chemical 

 action at the surface of the iron ; that it is not due to occlusion 

 of gases ; that it is not due to differences in conductivity in 

 iron at different temperatures, as suggested by Forbes ; that 

 there is a rise of temperature not only at the surface, as has 

 been shown by Barrett, but also throughout the mass ; that 

 this rise of temperature will partly account for peculiarities — 

 (1) in the thermoelectric properties, observed by Tait ; (2) in 

 the electrical conductivity, observed by Smith, Knott, and 

 Macfarlane ; (3) in the thermal expansion, observed by Gore 

 and by Barrett ; (4) in the rigidity, observed by Toinlinson 

 and independently by myself ; (5) in the viscosity, observed 

 by myself, and probably by Barus and Strouhal, though I 

 cannot find mention of it ; (6) in the possibility of hardening, 

 observed by myself ; (7) in the return of magnetic properties, 

 recorded by many observers. 



My present aim is to find out the cause of this rise in 

 temperature ; and my belief is that it is an internal chemical 

 action ; and the question is, What is this action ? I hope to 

 clear the matter up by experimenting upon specimens of 

 known composition. So far as I have gone I have come 

 across very curious differences in the effects shown by 

 different chance specimens. In some specimens the reglow 

 takes place much more leisurely than in others ; sometimes 

 it is practically a flash, and at other times it is not perceptible 

 at all with the most careful observation. I reserve a detailed 

 account of my observations, and at present will only mention 

 in this connexion that I am not inclined to attribute any 

 important part in the phenomena to the appearance of mag- 

 netic properties ; and I realize how, if my view of the cause 

 of reglow is correct, a difficult field for inquiry is opened out, 

 necessitating the production of evidence that the properties 

 of iron are different above and below the temperature of the 

 reglow phenomena, or, rather, that the temperature-coefficients 



