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XVI] NEW MATERIALS AND CONCLUSION 277

sheets are cast ‘on a very large casting frame I 7 feet long by
some 16 feet wide‘.’

Milled lead was invented during the last quarter of the seven-
teenth century, that time of change, when the modern period began
in building construction. Early milled lead was rolled in lengths
of 34 feet, which was twice the length of the largest casting table,
but the manufacturers made the easily understood mistake of rolling
it too thin. At Greenwich Hospital, which had been covered with
milled lead, ‘it rained in almost all over the hospital,’ in the year
1700, from which it would appear that milled lead was used by Sir
Christopher Wren. ‘Parliament sent the master and wardens of
the Plumbers’ Company to view it, and they unanimously declared
that milled lead was not fit to be used’ on buildings“. The
prejudice against it lingered on until the nineteenth century.

Lead seems to have always been laid upon boarding, as it is
at present, and in the Middle Ages in the North such boards were
known as sarking boards, and the word has survived in the dialect
of Northumberland. The word ‘ sark’ is an Old English word for
shirt, and is used with that meaning in Beowulf, so that sarking
was that which clothed the building like an under-garment, and
was an apposite simile of the early builders.

The favourite joint or seam between laid sheets of lead was
formed by wrapping the edges of the two sheets together into a
kind of semicircle, and in the year 1736 the one piece of lead was
called ‘orlop’ (probably o’erlap), and the other the ‘stander,’ and
the tools used to make the joint were a ‘dresser’ and a ‘seaming
mallet.’

Concrete is another material of which the use on a large scale
is a modern development. Although we have seen that various
forms which approached it were used in the past, such as walls
roughly built of mortar and small rubble, and ‘lime ash’ used in
floors, the use of concrete proper only arose with the increase of
large engineering works during the nineteenth century.

I Dance, in the year I 770 ‘having to sink the principal founda-
tions of Newgate prison to a depth of 40 ft., in consequence of
their site being partly on the ancient ditch of London wall, threw
into the bog cartloads of whole and broken bricks and cartloads of

1 ‘ External Leadwork ’ in The Arts Connected with Building, p. 191.
Dictionary oft/1e A ro/zitectural Publication .S'ociety, 5.7). Lead.

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