METALLURGICAL METHODS AT BROKEN HILL. 291 
in my opinion, to the alumina changing its functions from that of 
a base toan acid. It has been experienced so often on different 
ores as to leave no doubt in my mind that its action is as stated. 
After a furnace has been at work for a day or two all trouble 
arising from the ‘‘ blowing-in” operation is gone if care has been 
exercised. The “ blowing-in” crust is some trouble if allowed to 
form ; but as a rule it is great want of attention that allows this 
to make. It is due to the ashes of the wood which was thrown 
in at first to ignite the coke, forming into a solid mass, through 
the first slag formed chilling in it. The mischief of it is that it 
prevents the lead reduced or added to the “blowing-in” charges 
from getting into the well, and unless holes can be driven through 
it into the lead underneath, the latter will most assuredly chill 
and cause endless trouble, worry, and expense. When the furnace 
has been running slag for about an hour, the ashes inside can be 
broken up by introducing an inch round bar through either tap- 
hole and running it well into the furnace in all directions with 
the aid of seven or eight men. The ashes then float out with the 
slag, and if this is done fairly often for the first hour or two all 
danger of a “blowing-in” crust is avoided. The blast pressure is 
gradually risen to the point settled on, 10 to 15 cz. usually, and the 
temperature of the lead in the well soon increases until at the end 
of twenty-four hours it is usually bright-red. With good ore and 
plenty of water free from lime or magnesia, the furnace should 
have a long and successful run. 
The largest output of lead that I know of from one furnace for 
twenty-four hours was 26 tons ; 166 tons of charge being smelted 
to produce this. The ore smelted consisted of carbonate of lead 
averaging about 35 per cent. to 45 per cent., and was, of course, 
the easiest smelting ore to be had. This happened at the British 
Mine when I had charge of the furnaces. The week’s output of 
lead at the same time was 167 tons. Carbonate lead ore is no longer 
found in any large quantities, and it is now carefully hoarded, so 
that if a furnace produces from 5 to 7 tons of lead a day it is quite 
equal to the average output. 
COST OF SMELTING. 
This varies from half-year to half-year; but, on the whole, has 
has steadily decreased, until at present it costs about 25s. a ton, 
including costs for superintendence, labour, repairs, water, fluxes, 
fuel, light, &c. In 1888 the cost of smelting amounted to 36s. 5d. 
per ton, with the pick of the ore to smelt. The costs given do not, 
of course, cover desilverisation expenses, insurance, carriage on 
bullion, &c., but are simply the actual expenses incurred on a ton 
of ore in the blast furnace department from the time the ore is 
received from the mine until the bullion is made and put in the 
railway trucks ready to be despatched for further treatment. 
