STEEL 



905 



being dependent on the quantity of air passed throiigh it; other circumstances being 

 alike. When, therefore, the desired quantity of air has passed through the metal, 

 the vessel is turned on its axis, and the fluid steel is poured out, as shown &tjig. 1910. 



1910 



It is then received in the casting-ladle, which is attached to the arm of a hydraulic 

 crane so as to be brought readily over the moulds. The ladle is provided with a fire- 

 clay plug at the bottom, the raising of which, by means of a suitable lever, allows 

 the fluid steel to descend in a clear, vertical stream into the moulds. As soon as the 

 first mould is filled, the plug valve is depressed, and the metal is prevented from 

 flowing until the casting-ladle is moved over the next mould, when, by raising the 

 plug, the second mould is filled in a similar manner ; and so on, until all the moulds 

 are filled. After the discharge of the metal from the vessel, the process should bo 

 repeated without delay, since the temperature of the interior of the vessel is greater 

 after the first charge than it was before, and consequently it is in a better condition 

 for the process. The vessel may be moved on its axis by suitable gearing, but it is 

 considered preferable to use hydrostatic pressure to effect every movement of the 

 crane and of the vessel; so that when operating on from 5 to 10 tons at a single 

 charge, the director of the process can, from a distant point, and with his own hands, 

 effect every movement required, by merely working the handles which turn on, or 

 off, the pressure of the water. He has also charge of the blast-cock, whilst the dial 

 for registering the number of cubic feet of air is before him ; and thus, by the 

 control of one responsible man, charges of several tons of crude cast iron may be 

 converted into malleable iron, or into steel, in a few minutes, and be cast into ingots 

 of any desired form and weight, suitable for large shafts, or for rolling into rails, 

 merchant bars, or plates. 



The slags of the Bessemer process vary considerably in composition from those of 

 the puddling furnace, being much more acid and approximate to the pyroxene formula. 

 At Horde, in Westphalia, a crystallised slag has been obtained which yielded, by 

 analysis : silica, 44'73 ; protoxide of iron, 20'59 ; protoxide of manganese, 32'74 ; 

 lime, 1-53; magnesia, 0-17 = 9976. 



Oxygen-ratio of silica to bases = 23 - 85 : 12'43. 



Specific gravity, 3 '08. 



The crystals were found to be of the regular augite form, the angles being inter- 

 mediate between those of the natural minerals, Pajsbergite and Babingtonite, as is 

 also their composition. 



The enormously high temperature developed by the action of cold air on molten 

 cast iron in the Bessemer process is obviously due to the extreme rapidity with which 

 the operation takes place, and the advantageous form of the converter for concentra- 

 ting the heat developed. For, although the reactions and consequently the heat pro- 

 duced ane in no way different from those of other finery processes, whether in the open 



