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LV. On Peculiarities observed in Iron and Steel at a Bright- 

 Red Heat. By H. F. Newall, M.A., Demonstrator of 

 Experimental Physics, Cambridge University* . 



IN the September number (p. 256) of the Philosophical 

 Magazine, which I am sorry not to have seen till last 

 week (Oct. 6), there appears a paper by Mr. Herbert Tom- 

 linson on a " Remarkable Effect on raising Iron when under 

 Temporary Stress or Permanent Strain to a Bright-red 

 Heat." I have been engaged for some time past on experi- 

 ments bearing on the subject of his paper, and as I hope 

 before long to be able to publish a full account of my experi- 

 ments, I will not at present do more than put down a few 

 notes on such of the more definite results that I have obtained 

 as seem to throw light on the interesting phenomena recorded 

 in Mr. Tomlinson's paper. 



First I will describe what I observe as to Reglow or 

 Recalescence. A wire (about 1 mm. diam.) steel or iron, of 

 certain composition, is heated gradually by a strong current 

 or in the name of a Bunsen burner ; it becomes luminous ; 

 the luminosity increases as the temperature rises, until a 

 certain point is reached, when in some cases it pauses in 

 its increase, in others it actually diminishes : this I will refer 

 to as the Darkening ; and then it increases again until the 

 wire melts. However, let the heating be stopped before 

 melting takes place and let the wire cool gradually, or, 

 rather, let it be placed in such circumstances as one would 

 naturally expect would promote gradual cooling : the lumi- 

 nosity decreases until a certain point is reached, roughly 

 speaking about dull red heat, when it ceases to decrease and 

 in some cases only pauses, in others it actually increases : 

 this is spoken of as the Reglow ; and then it diminishes 

 again until the wire is no longer luminous. 



I am still working with a view to finding out to what 

 differences in composition are to be attributed the differences 

 observed in the effects just described. I am fortunate enough 

 to have enlisted the interest of Col. Dyer, of Lord Arm- 

 strong's firm, and of Mr. Jenkins, of the Consett Iron Works, 

 and of Mr. Firth, of Sheffield, who have most kindly supplied 

 me with many specimens of steel of known composition. 

 After a great many experiments and observations, — many of 

 them merely careful repetitions and extensions of Gore's 

 results and of Barrett's, many of them, however, new, — I 



* Communicated by the Author. 



