PROGRESS IN THE MANUFACTURE OF STEEL'. 813 



an intense white heat. Bessemer at first used extraneous heat to start 

 the process, if not, indeed, during its progress, which shows that he 

 was not then aware that the heat created by merely blowing in air 

 would be sufficient. In his next patent he dispensed Avith the furnace 

 around the crucible, and, instead of tapping the crucible from the bot- 

 tom, he mounted it on trunnions, and, by tipping it up by machinery, 

 poured the contents from the mouth. This apparatus is essentially 

 the same as that used at the present day. It was soon found that, to 

 produce steel by this process which would work properly, manganese, 

 if not originally present, would have to be added. In the absence of 

 manganese, sulphur and oxygen, in anything more than very minute 

 quantities, make the steel crumble when worked at a red heat ; it is 

 said to be " red short." In the case of the oxygen, the manganese 

 combines with it, and passes it into the slag ; but with sulphur the 

 reaction is different ; its injurious effect is simply counteracted by the 

 manfranese : it is not removed from the steel. At first mang^anese was 

 only employed in the form of sj^iegeleisen ; but this use was liable to 

 the difficulty that if enough spiegel was added to impart the requisite 

 quantity of manganese, too much carbon would have been introduced, 

 and alloys richer in manganese known as ferro-manganese have 

 been souo-ht and found. 



By adding at the end of the process a known quantity of spiegel 

 or ferro-manganese, containing a known quantity of carbon, steel of 

 any required hardness could be obtained. 



The year which saw the birth of the Bessemer process was doubly 

 remarkable, for it was at that time that the regenerative system of 

 heating was first introduced by Dr. Siemens. Nothing can be simpler 

 than the principle involved in this method, yet it was destined to play 

 a most important part in the progress of the arts. The idea was to 

 store up the heat escaping in the waste gases from furnaces, and to 

 employ it to raise the temperature of the gas and air previous to their 

 combustion in the furnace. This was accomplished by causing the 

 spent gases to pass through two chambers filled with loose brickwork. 

 "When these chambers have become heated to a high temperature, the 

 waste gases are made to pass through two other similar chambers, and 

 the air and gas necessary for combustion in the furnace are caused to 

 pass through the highly heated regenerators. By causing the ingoing 

 gases to pass alternately, at suitable intervals of time, through each 

 pair of regenerators, a very high and, at the same time, uniform tem- 

 perature can be obtained in the furnace, without any greater con- 

 sumption of fuel than in the older methods. The success of this 

 process depended entirely on the fuel being first converted into a 

 combustible gas. This was done in a chamber to which only sufficient 

 air is admitted to convert the carbon into carbonic oxide, which is 

 then conducted by tubes to one of the regenerators to be heated, and 

 thence to the furnace, where, coming in contact with air which has 



