284 PROCEEDINGS OF SECTION B. 
until it gets considerably below the obnoxious crust or scaffold. 
Then the blast is taken off the furnace, and the crust is prised off 
with heavy 14-inch diameter-octagon steel bars. The disadvantage of 
the cementation of the crust with the brick walls is then seen. 
The crust being all of a dull, red heat, you may chip pieces off 
with laborious effort, but that is all. If you attempt to clean the 
walls to the original form of the furnace, you find thas the crust 
has become part and parcel of the brick shaft, and the latter gets 
very much damaged in the operation, 
With the water-jacket walls the crust is a very different con- 
cern. Instead of being a solid, tough, and immovable obstruc- 
tion, you find that there is but one place in it that is hard, which, 
naturally, is the face exposed to the heat of the furnace. Behind 
this hard face is a mass of loose ore, which falls away as soon as 
the hard shell on the outside is destroyed. Then the crust does 
not form any sooner on the cold water jacket than it does on the 
brick shaft, because the attrition of the descending ore charge has 
effect on its peculiar form, and it is much more easily removed 
from the cold iron face, usually in six hours, leaving the furnace 
its original size. With the brick shaft this may take twelve to 
eighteen hours, and when left at that is not anything like clean, 
through the fact of the crust having filtered into the pores of the 
brick, and made itself a part of the structure as before described. 
Much has been said against the water-jacket shaft on the ground 
of increased fuel necessary through the amount of caloric carried 
off by the water ; but I think a nice looking mathematical calcu- 
lation is not sufficient to overcome the great advantages which the 
water-jacket shaft has over the brick, and besides that I never 
used more fuel with the water-jacket furnace than with the brick- 
shaft furnace. 
It is no uncommon thing to see a number of the brick-shaft 
furnaces being “burnt out,” as it is called, just above the lower 
jackets. Unskilful work is the natural retort; but I maintain 
that with the irregularity in composition of the ore, this might 
naturally be expected. Such a trouble is never experienced with 
the other style of shaft, and the test of experience has demon- 
strated indisputably that for good, fast, clean, and cheap work, 
the blast furnace which is all water-jacketed is the ideal model 
lead-blast furnace. 
Such a furnace may be described as follows :— 
It is water-jacketed throughout. The top half of the furnace 
consists of hollow wrought steel jackets with a 6-inch water space, 
three jackets being 9 feet 9 inches deep ; the fourth, recessed to 
carry the flue of downcast, is 8 feet deep. The water is fed in 
at the bottom of each jacket, with the view of preventing the 
deposition of any sediment, and the whole of the jackets are con- 
nected to make sure of an equal water circulation through *hem 
