504 PROFESSOIi W. X. HAliTLEY AXD ^IR. II. RAM AGE OX THE SPECTRA 
the “ basic” lining of the vessel. Such ignition could only take place at this stage in 
consequence of the combustion of highly heated carbon monoxide or a hydrocai'bon, 
and the presence of tliis latter substance is easily accounted for. 
We conclude that the immediate production of a flame is caused not by the oxida¬ 
tion of material in the bath of metal, but by carbonaceous matter in the lining of the 
converter ; that its luminosity is due partly to the volatilisation of the alkalies or 
alkali metals, but certainly prior to this eflect to the incandescence of a cloud of lime 
dust carried up by the blast into the flame. 
Secondly, volatilisation of metals occurs Largely at an early period in the blow, and 
is due to the diiference in the composition of the metal bloAvn. In the “ acid ” 
la’ocess the crude metal contains much silicon, carbon, and mano-anese. The cornbina- 
tion of the silicon and manganese with oxygen is ihe cause of the high temperature 
attained withoul any indication of the flame which subsequently appears, for both the 
products of combustion of silicon and manganese are liquid slags at that high tem- 
]:)erature. In the “basic” process the combustion of carbon takes place at a much 
eailier period, because there is practically no distinct period "udien siliceous slags are 
formed; with the carbon monoxide the metals are volatilised, the atmosphere being 
a inducing one. 
Thirdly, a very large amount of fume is formed at the close of the second period. 
This arises from the oxidation of metal and of phosphorus in the iron phosphide being 
productive of a high temperature, but little or no carbon remaining in the bath ; the 
flame is comparatively short, and the metallic vapours carried up are burnt by the 
blast. 
Fourthly, the over-blow is characteiised by a very powerful illumination, from 
what ajipears to be a brilliant yellow flame which is generated within the vessel. 
During this over-blow there is a copious production of dense fume, composed of 
oxidised metallic vapours, chiefly iron. The particles forming the fume are undoubt¬ 
edly of very minute dimensions, as is proved by the fact that they scatter the light 
which falls upon them and cast a brown shadow, and the cloud of fume ascends to a 
great height before it is dispersed. Such small particles while within the vessel are, 
doubtless, at the same temperature as the escaping gases. The spectrum of the 
over-blow is continuous and very feeble in the ultra-violet, as it does not extend 
beyond wave-length 4000. This indicates that the source of light is at a compara¬ 
tively low temperature, approacliing that of a jmllowish-white heat. We conclude, 
therefore, that the source of light, or w4iat apparently is a flame, really emanates 
from a torrent of very small particles, liquid or solid, at a yellowish-white heat. 
From the S]3ectrum measurements we have evidence that the source of light during 
the over-blow is at a much lower temperature tlian that which prevails during the 
first period, when the highly heated carbon monoxide is undergoing combustion. This 
is suflicient to account for the feeble character of tlie line spectra of the alkali metals, 
&c., seen at this stage in the band of continuous rays. But a second reason for this 
