stance, considering its importance, and a reproach to those chemists
who have had it in their power to ascertain its nature.
Calcareous spar crystallized in dodecahedrons sometimes also occurs
in this vein. So I am told does sulphate o f barytes; but I was not
so lucky as to observe any specimens of that rare mineral in Sweden,
though so abundant in Great Britain. Specimens o f mountain cork
likewise occur occasionally. I saw several preserved in a small mineral
cabinet belonging to the mine. There is also a mineral occasionally
met with, (though I did not see it,) which is considered in Sweden as
the Aplome o f Haiiy. Its colour is brown, and it occurs crystallized
in irregular dodecahedrons with trapezoidal sides. It has but little
lustre, and its specific gravity is 3 -902. According to the analysis o f
C. A. Murray, its constituents are as follows;
Silica..........................................34*04
Alumina....................................18*07
Lime. : . . . . 1 ........................... i6*sG
Magnesia.................................. 0*06
Oxide o f manganese. ........... 23*51
Oxide o f iron .................... 10*03
102*77
The ore is broken into small pieces and then roasted. It is then
put into conical-shaped furnaces, constructed o f the slag from cast
iron, which is found to answer the purpose fully as well as bricks, and
to come much cheaper. In these furnaces it is mixed with the requisite
quantity o f charcoal, but the addition o f limestone is seldom
necessary, because it exists already in the ore. Here it is melted and
separated from the slag, which is allowed to run off or cast into
bricks according as it is wanted. The cast iron obtained by this process
is as white as silver, completely crystallized, extremely hard and
brittle, and incapable of being applied to any useful purpose in that
state. It is not liable to rust, and indeed this is a quality which Dan-
nemora iron possesses, both in the state o f cast and malleable iron. I t
is much less liable to rust than any other kind o f iron whatever.
This cast iron is reduced to malleable iron by heating in a bed o f
charcoal and oxide of iron, and hammering it out into bars while hot.
In this state it is whiter than common iron, o f a distinctly fibrous texture,
and much stouter than any other species of iron whatever. It
goes all to England, and indeed the greatest part of it is purchased by a
particular merchant in Hull. In this country it is converted into steel.
I was told in Sheffield, that they have not been able to make cast
steel from any other iron but the iron of Dannemora. The best Dan-
nemora iron is marked by three balls. This is the kind which is
manufactured by Mr. Tamm. He politely supplied me with abundance
of specimens o f his iron in all states, for the purpose o f chemical
examination.
Mr. Tamm has likewise a manufactory o f steel by cementation.
The process seemed to me to be exactly the same with that employed
at Sheffield, and in other parts of Great Britain, for the same
purpose. The steel remains in the. bed of charcoal nine days. The
firewood is birch, which yields more heat than any other species of
wood used as firewood in Sweden. The two steam engines at Dannemora
are at present kept going by means o f wood. But if is intended
to import coals from England for that purpose, which no doubt
would be a considerable saving. The Swedish coals are at such a distance,
so inferior in value, and so high priced, that the employment of
them is out of the question.
The cause o f the superiority o f Dannemora iron has never been explained.
Some conceive it to be owing to the presence o f manganese.
Berzelius ascribes it to the presence of the metal of silica; while a
third party, with some appearance of reason, ascribe the greatest part
of the superiority to the process employed. I was even assured by
one gentleman, who has bestowed particular attention to the subject,
that by following a similar process he has obtained as good iron from
other Swedish ores. But that something is due to the ore itself is evident,
I think, from this circumstance, that the quality o f the iron
(though the same process, is followed, I presume, by all,) differs a good
deal, according to the part o f the vein from which the ore was taken.