In 1831, Neilson's hot blast specification had been published for two
and a half years only. The Butterly Company had tried the hot blast
for the first time in the November preceding the meeting of the
British Association. The heating of the blast was coming very slowly
into use, and the temperature attained when it was employed was only
some 600 degrees. The ordinary blast furnace of those days was 35 to
40 feet high, and about 12 feet diameter at the boshes, and turned out
about 60 tons a week. It used about 2½ tons of coal per ton of iron,
and no attempt was made to utilize the waste gases, whether escaping
in the form of gas or in the form of flame, the country being
illuminated for miles around at night by these fires. The furnaces
were also open at the hearth, and continuous fire poured out along
with the slag.
In 1881, blast furnaces are from 90 ft. to 100 ft. high, and 25 ft. in
diameter at the boshes; they turn out from 500 to 800 tons a week. The
tops and also the hearths are closed, and the blast--thanks to the use
of Mr. E.A. Cowper's stoves--is at 1,200 degrees. The manufacture of
iron has also now enlisted in its service the chemist as well as the
engineer, and among those who have done much for the improvement of
the blast furnaces, to no one is greater praise due than to Mr. Isaac
Lowthian Bell, who has brought the manufacture of iron to the position
of a highly scientific operation. In the production of wrought iron by
the puddling process, and in the subsequent mill operations, there is
no very considerable change, except in the magnitude of the machines
employed, and, in the greater rapidity with which they now run. In
saying this, I am not forgetting the various "mechanical puddlers"
which have been put to work, nor the attempts that have been made by
the use of some of them to make wrought iron direct from the ore; but
neither the "mechanical puddler" nor the "direct process" has yet come
into general use; and I desire to be taken as speaking of that which
is the ordinary process pursued at the present in puddled iron
manufactures. In 1831, a few hundredweights was the limit of weight of
a plate, while in 1881, there may readily be obtained, for
boiler-making purposes, plates of at least four times the weight of
those that were made in 1831. I may, perhaps, be allowed to say that
there is an extremely interesting blue-book of the year 1818,
containing the report of a parliamentary committee which sat on boiler
explosions, and I recommend any mechanical engineer who is interested
in the history of the subject to read that book; he will find it there
stated that in the North of England there was a species of engines
called locomotives, the boilers of which were made of wrought iron,
beaten, not rolled, because the rolled plate was not considered fit;
it was added that if made of beaten iron the boiler would last at
least a year.
In 1831, thirteen years later, the dimensions of rolled plates were no
doubt raised; but few then would have supposed it possible there
should be rolled such plates as are now produced for boiler purposes,
and still fewer would have believed that in the year 1881 we should
make, for warlike purposes, rolled plates 22 inches in thickness and
30 tons in weight. I have said there is very little alteration in the
process of making wrought iron by puddling, and I do not think there
is likely to be much further, if any, improvement in this process,
because I believe that, with certain exceptions, the manufacture of
iron by puddling is a doomed industry. I ventured to say, in a lecture
I delivered at the Royal Institution three years ago on "The Future of
Steel," that I believed puddled iron, except for the mere hand wrought
forge purposes of the country blacksmith, and for such like purposes,
would soon become a thing of the past. Mr. Harrison, the engineer of
the North-Eastern Railway, told me that about eighteen months ago the
North-Eastern Railway applied for tenders for rails in any quantities
between 2,000 and 10,000 tons, and they issued alternative
specifications for iron and for steel. They received about ten
tenders. Some did not care to tender for iron at all; but when they
did tender alternatively, the price quoted for the iron was greater
than for the steel. I have no doubt whatever that, in a short time, it
will be practically impossible to procure iron made by the puddling
process, of dimensions fit for many of the purposes for which a few
years ago it alone was used.
With respect to steel, in 1831 the process in use was that of
cementation, producing blistered steel, which was either piled and
welded to make shear steel, or was broken into small pieces, melted in
pots, and run into an ingot weighing only some 50 lb. or 60 lb. At
that time steel was dealt in by the pound; nobody thought of steel in
tons. In 1881, we are all aware that, by Sir Henry Bessemer's
well-known discovery, carried out by him with such persistent vigor,
cast iron is, by the blowing process, converted into steel, and that
of Dr. Siemens' equally well-known process (now that, owing to his
invention of the regenerative furnace, it is possible to obtain the
necessary high temperature), steel is made upon the open hearth. We
are, moreover, aware that, by both of these processes, steel is
produced in quantities of many tons at a single operation, with the
result that as instanced in the case of the North-Eastern rails, steel
is a cheaper material than the wrought iron made by the puddling
process. One cannot pass away from the steel manufacture without
alluding to Sir Joseph Whitworth's process of putting a pressure on
the steel while in a tried state. By this means, the cavities which
are frequently to be found in the ingot of a large size are, while the
steel is fluid, rendered considerably smaller, and the steel is
thereby rendered much more sound. In conclusion of my observations on
the subject of iron and steel manufacture, I wish to call attention to
the invention of Messrs. Thomas & Gilchrist, by which ores of iron,
containing impurities that unfitted them to be used in the manufacture
of steel, are now freed from these impurities, and are thus brought
into use for steel-making purposes.