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274 NEW MATERIALS AND CONCLUSION [CH.

irons; riveted to a vertical plate in the middle of them.’ This
form has become standardised, and the horizontal pieces at the top
and bottom are known as the top and bottom flange, and the
connecting vertical piece is known as the web; since 1866 the
joists or girders have been rolled whole with all the plates in
one'piece. The ‘built’ up girders have also continued in use.

Changes in building materials now take place rapidly and mild
steel has superseded rolled iron for structural purposes; the writer
remembers the hesitation with which it was adopted by architects,
when it began' to take the place of iron, a quarter of a century
ago. The forms of the steel joists followed those which had been
adopted for rolled iron. In the year 1886 it was said that
Bessemer’s process for steel, which dates from the year 1858, was
‘one which may tend to do away .with all mere cast or wrought
iron in building constructionl,’ and the prophecy has'come true
with respect to purely constructional work.

The attitude of architects to constructional ironwork, half a
century ago, when its use was becoming common, may be under-
stood from the following extract from a lecture by Professor George
Aitchison at the Royal Institute of British Architects, in February,
1864. He said: ‘The use of iron has become so general that it
has nearly usurped the place of other materials. In every con-
struction, machine, tool, or article of domestic use, we may find
iron doing duty not unfrequently in the most unexpected ways and
places—Architects, therefore, must not alone refuse to profit by the
advantages it offers, or, when they are absolutely obliged to use it,
give it a sort of grumbling recognition and put it out of sight.
Many have used it with success, but by the profession generally it
is avoided”.’

There is as little finality to the varieties of building materials as
there is to the methods of construction, or to the styles of architec-
ture. At present the constructor of buildings uses the material
which experience has shown to be most suitable at #26 price.
There is a choice of metals in building, as there is of styles for
architectural design, but the choice is more logically exercised.
Lead is used generally for water pipes, often for flashings, fre-
quently for gutters, and sometimes for flats. Wrought iron, the
ancient form of the metal, is still used for the old purposes of hinges
and grilles, and gates and railings. Its use in England has been

1 Dz'rlionary oft/2e Architectural Pub/{ration Safely, 5.7x. Steel. 2 Ibid. $.22. Iron.

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