1088 
PROFESSOR W. N. HARTLEY ON 
whole remaining period of the blow, this metal being of similar composition to that 
blown at Dowlais. 
It must, however, be remembered that the higher temperature at Dowlais would, if 
acting upon manganese slag, produce a spectrum more similar in character to that 
obtained from ferro-manganese or spiegel-eisen than that obtained at Crewe, but the 
iron lines in these circumstances would also be stronger. 
The connection between the termination of the blow and the drop of the flame is 
to be explained exactly as in the case of the spectrum at Ci’ewe, the difference in the 
two spectra being due to the quantity of vapour of manganese in the flame. 
The Technical As'pect of this Investigation. 
Long experience has shown that in England, in Styria, and at Seraing, in Belgium, 
the use of the spectroscope has rendered substantial service in determining the end of 
the operation in the Bessemer converter, notwithstanding that the nature of the 
spectrum observed was not accurately ascertained, nor the cause of its production 
well understood. The reason of this is not far to seek, when we consider that towards 
the close of the “ fining stage” the indication is particularly distinct, for it culminates 
in the disappearance of the bright lines and flutings of manganese, whether these 
proceed from the pi'esence in the flame of material vaporized directly from the metal 
itself, or from the slag which is formed from the oxidation of elements contained in 
the metal during the first period. The quantity of grey cast iron, of spiegel-eisen, or 
ferro-manganese, which is finally added, determines the hardness of the steel, and the 
composition of the added material is ascertained with exactitude by means of frequent 
analyses. 
By this means a metal is obtained which is much more constant in comj^osition than 
when the process is interrupted before the completion of decarburization, and when, 
after the result of a test of the metal, spiegel-eisen is added and blowing is resumed 
for a few minutes. It was the aim of managers of steel works in the early days of 
the process to cease blowing before complete decarburization, in order that the neces¬ 
sary proportion of carbon might be left in the charge ; but it was found that there 
was no certainty in being able to produce the same quality of metal at each “ blow.’’ 
It will be seen from the results of this investigation that the thermo-chemical 
operation involved in blowing could not be always carried out exactly under the same 
conditions, or within the same precise limits of time; the initial temperature of the 
metal, and even the temperature of the converter into which the charge is allowed to 
flow, can affect the rate of combustion of the carbon, and the oxidation of the man¬ 
ganese and s’dicon; and, furthermore, it must be borne in mind that, with successive 
charges from the same blast-furnace, the composition of the metal varies to an extent 
which can easily upset all previous calculations. When the charges come from 
diflerent furnaces, further complications and increased difficulties arise. As there is 
