﻿with Coloured Glasses and with the Spectroscope, 3 



In the second period the discharge of slag increases, and the 

 flame is very bright and illuminating with occasional dark 

 streaks. Through the glasses at the beginning of this period 

 the flame is of an ashy-blue colour with streaks and flashes of 

 crimson, the edges being sometimes of a purplish hue. At 

 this point surrounding objects are illuminated, and the converter 

 becomes distinctly visible. A wreath of crimson is seen sur- 

 rounding the flame where it strikes the chimney. By the middle 

 of this period the crimson almost entirely disappears from the 

 body of the flame, leaving only a slight cone at its base, and a 

 border of greenish hue makes its appearance and gradually 

 grows more decided. Streaks of a dark blue colour are also 

 seen in the body of the flame. 



The beginning of the third period is scarcely indicated to the 

 naked eye, though the flame becomes somewhat weakened, and 

 after a few minutes shows dark streaks running through it. 

 Through the glasses, at the commencement of this period the rose- 

 coloured cone begins to expand and deepen, the greenish sheath 

 is more decided, while streaks of dark and green are visible. 

 After a few minutes the change becomes very rapid, a few 

 seconds only being required to reduce the flame from rose- 

 colour to the deep crimson non-illuminating gas as at first, and 

 again the converter is lost to view, by which time the blast 

 should have been turned off. 



The gradual fading of the crimson from the beginning of 

 the blow and its deepening at the termination of the process, as 

 well as the crimson band at the base of the flame and the 

 wreath of crimson surrounding the flame at the chimney, tend 

 to confirm Mr. Rowan's views, which are that the different 

 shades of crimson are due to changes of temperature. The 

 stream of gas which comes from the mouth of the converter 

 at the beginning of the process being illumined from within, 

 derives its colour from the metallic bath, the temperature of 

 which, owing to the combustion of silicon, increases more ra- 

 pidly during this period than at any other. 



The crimson band at the base of the flame and the wreath of 

 crimson at the chimney might also be accounted for by this 

 theory. The flame rushing from the mouth of the converter 

 has a tendency to create a vacuum at its base around the con- 

 verter's edge, and thus to cause a wreath of flame to pass over 

 this surface, and by consequent cooling produce the crimson 

 band. The wreath of crimson at the chimney may be also clue 

 to the cooling of the flame consequent upon deflection. 



It is true we have a seeming contradiction to this theory in 

 the rose-coloured cone extending from the base at the centre, 

 which we should naturally consider the hottest part of the flame ; 



B 2 



