METALLURGICAL METHODS AT BROKEN HILL. 283 
At this point the expenses incurred are then charged to the ore- 
smelting account. They serve to show what the bare furnace, and 
starting it in work, costs without building, engine, fuel, or stack. 
No estimate has been given of these, because the condition of one 
furnace by itself does not exist in Broken Hill ; all the smelting 
works there being on a much larger scale, with everything to 
correspond as regards building, flue, and stack capacity. 
[A general design of a complete plant with two brick-shaft 
furnaces and space for others was exhibited. | 
THE WORK ON THE FURNACE. 
The old style of oval-shaped (horizontal section) 30-ton blast 
furnace, with a short iron stack through the roof to carry off the 
smoke—with which the era of lead-smelting was inaugurated at 
Broken Hill—is now obsolete, and the sight of three or four of 
these old furnaces on the scrap heap of the mine forcibly brings 
home the advancement which has been made in the general con- 
struction of the lead-blast furnace. 
The first radical change in design was made when Mr. H. H. 
Schlapp, late Metallurgist of the Broken Hill Proprietary, intro- 
duced the present furnaces at Broken Hill. Alterations were 
made in these by Mr. Schlapp, which improved them and at the 
same time made them “ handier” furnaces, and since Mr. Schlapp’s 
departure from Broken Hill, other small improvements, such as 
the introduction of the Matthewson matte separator, have assisted 
toward more economical work, which the fall in the silver market 
and assay contents of the ore demanded. 
At the British Mine, a more important change was made in the 
design by Mr. John Howell, who substituted mild steel jackets 
for the brick shaft of the furnace of Mr. Schlapp’s design ; and 
for ores which contain sulphide of lead, my experience has un- 
doubtedly shown that this change has been a most important one. 
One great trouble in a lead furnace when smelting sulphide ore, 
with or without zinc, is the manner in which the sulphide causes 
the formation of “crusts” or ‘ scaffolds” in the furnace at a 
point about 12 inches to 18 inches below the level of the top of 
the ore charges in the furnace. As the Jead sulphide reaches 
the smelting zone of the furnace, part of it sublimes and ascends 
through the loose ore and deposits again on the cooler walls of 
the furnace. With a brick furnace, the walls of the shaft are 
never so cool, of course, as the water-jacketed shaft mentioned, 
and the sulphide of lead and zinc seems to incorporate itself with 
the bricks, as if it were a part of the original erection. When 
this crust grows to such a size as to materially interfere with the 
working of the furnace, it is usual to “‘run the furnace down,” to 
use a technical term, or, in other words, stop putting fresh charges 
into the furnace and allow the level of the ore and fluxes to sink 
