448 
Iron . 
much heated) is never liable to this fallacy. The objefet of this 
experiment is obvious. It is well known that a solution of sul- 
phat of iron (and indeed of all the salts of iron) deposits its base 
after standing* some time, because the iron becomes too much 
oxyded to remain in solution, and yet after this spontaneous pre- 
cipitation had taken place, the iron is only what is called an ochre, 
is perfectly magnetic after slight roasting, and is the same in ef- 
fect as the bog ores in the greater part of all countries which 
abound in pyritous stone coal. (Vide Henckel’s Pyritologia). 
Therefore it is evident that the ore in this experiment did not 
contain a full dose of oxygen, or else it would have been insoluble, 
still less could it contain a quantity of it destructive to its pro- 
ducts in the blastfurnace, since it actually contained less than the 
class of bog ores, which are acknowledged to be among the easiest 
worked, of all the ores of iron. 
It is to be lamented that a man of such perseverance, expe- 
rience and skill in the manipulations of the assay furnace, should 
have entertained so strong an impression of the injurious tendency 
of oxygen, and overlooked so obvious and powerful a mineralizer as 
sulphur is known to be. Perhaps the reason was that he conceiv- 
ed no notable portion of sulphur could exist in combination with 
the one unless it appeared plainly in the roasting, for he says ex- 
pressly that if the pulverized ironstone be thrown into a red hot 
vessel, the presence of sulphur (if any !) will instantly be mani- 
fested by a dark lambent flame and a suffocating vapour. Now 
1 can assert, upon my own experience, that an ironstone which 
contains so much sulphur as to produce but little and extremely 
bad iron in the furnace and in the assay crucible, may notwith- 
standing be thrown to the quantity of four ounces upon a red hot 
iron plate without exhibiting any flame or emitting any percepti- 
bly sulphureous odour. That consequently, this mode of disco- 
vering sulphur cannot in my opinion be at all relied on. Certain 
it is indeed, that where these appearances are present, the ore 
must be exceedingly sulphureous, but it is equally certain that 
ironstone may be contaminated with sulphur to a very mischievous 
excess, without shewing any such appearances whatever when 
tried in the mode which he recommends ; although when a very 
large quantity is burnt in a pile and for several days together as at 
furnaces, the sulphureous acid gas can be readily perceived even 
at several yards distance. The cause of this odour, cannot be mis- 
taken where wood and charcoal are used for the purpose of torre- 
