234 -THE SCIENTIFIC PAPERS OF 



A fire space is provided surrounding each hopper, through 

 which flame ascends from the furnace, and is allowed to escape in 

 regulated quantities near the upper extremity of the retort, the* 

 object being to heat the latter and the ore contained in it to a red 

 heat. A wrought-iron pipe descends into each hopper from a 

 general gas-tube above, through which a current of ordinary pro- 

 ducer gas is forced in amongst the heated ore. The propulsion of 

 the gas is effected most conveniently by means of a steam-jei 

 in the gas-tube leading from the main gas-channel to the top of 

 the furnace, care being taken to effect a total condensation 

 of the steam by passing the gas finally through a small 

 scrubber, in which water trickles over pieces of coke. In this 

 way the gas is at the same time purified from sulphurous acid, 

 the sulphur of which might otherwise combine with the reduced 

 ore. 



The furnace is charged in the following manner : 



The hoppers and gas-pipes being placed in position, about \ cwt. 

 of charcoal is charged through each hopper to form a basis for the 

 ore with which these are afterwards filled. 



About 10 cwt. of pig-metal is charged through the ports at the 

 back or front of the furnace, which, upon being melted, forms a 

 metallic bath below the hoppers. In the meantime, the ore in 

 the lower parts of the hoppers, being heated in an atmosphere of 

 reducing gas, has become partially reduced into metal sponge, 

 which, in reaching the metallic bath, is readily dissolved in it, 

 making room for the descent of the superincumbent ore, which is 

 likewise reduced in its descent and dissolved in due course, fresh 

 ore being continually supplied on the charging platform. The 

 dissolution of the reduced ore proceeds with extraordinary 

 rapidity, but is practically limited by the time necessary to 

 effect the reduction of the ore in the hopper which occupies 

 several hours. It is, however, not essential that the ore should 

 be thoroughly reduced before reaching the bath, because the 

 carbon contained in the cast metal serves also to complete the 

 operation. 



I prefer to employ a mixture of hematite and spathic ore, 

 containing the elements for forming a fusible slag, which will 

 accumulate on the surface of the metallic bath, and may be from 

 time to time removed through the centre door. If the ore con- 



