Iron . 
449 
faction, as is generally the case in the United States ; but where 
stone coal is employed, for that purpose, as it is in Scotland, it 
might very readily escape notice. 
I shall pass by some of Mr. Mushet’s intermediate observa- 
tions upon this subject, and proceed at once to his conclusion, 
Which I conceive would in many cases produce very injurious ef- 
fects if reduced to practice. « I look upon it” says he “ to be a 
desideratum in the preparation of ironstone, to contrive a mode 
which would either deoxygenate the ore unexposed to external 
air, with a degree of certainty which would preclude the possibili- 
ty of the ore’s attracting more oxygen.” The meaning of which 
appears to be, to exclude as much as possible the action of the at- 
mosphere. 
Before I make any further remarks upon Mr. Mushet’s theory* 
I shall lay down what I consider the objects and rationale of the 
roasting of ores of iron previous to their entrance into the furnace. 
To do this the more readily I shall divide them into two classes. 
1st. Comprehending those ores which do not contain any percep- 
tible portion of sulphur or arsenic. 2d!y. Those ores which are 
considerably mineralized by one or both. 
Now, when ores of the first class are too large to be put into 
the furnace without breaking, and too hard to be broken without 
the assistance of heat— they are roasted ; and although every ma- 
nufacturer may not know the reason of the operation, it is simply 
this, that they may be broken in smaller pieces and with less la- 
bour. The proof of this is, that all the bog ores without exception 
are used raw, although they contain fully as much carbonic acid, 
water and oxygen as any ore whatever. Moreover when moun- 
tain ore occurs small enough to do without breaking, as is some- 
times the case, the operation of roasting is omitted also. I have 
seen instances of this last at Warwick and Ioanna furnaces of this 
state, where they'used their ore without any preparation, and have 
myself in a case of emergency, had a considerable quantity of raw 
ironstone put into the furnace without any bad consequences re- 
sulting from it. Consequently we may safely assume it as a de- 
cided fact that the presence of water and carbonic acid in the ore 
has no injurious effect upon the operation of smelting. 
Let us on the other hand consider torrefaction as applied to an 
ironstone containing a quantity of sulphur. Here we shall have 
to operate upon a substance, known to possess a strong attraction 
to iron in all proportions from 1 to 55 per cent, and in all these 
