Archimedes Texts

Of the Girders of Stone, of the Ligament and Fortification of the Cornices,
and how to unite several Stones for the strengthening of the Wall.

A mong the Girders we reckon those Cour
ses of large Stone which tie the out
ward Shell to the Inward, and which bind the
Ribs one into the other, such as are those
which we said in the last Chapter ought to be
made every five Foot. But there are other
Girders besides, and those principal ones,
which run the whole Length of the Wall to
embrace the Corners and strengthen the whole
Work: But these latter are not so frequent,
and I do not remember ever to have seen
above two, or at most three in one Wall.
Their Place is the Summit of the Wall, to be
as it were a Crown to the Whole, and to per
form the same Service at the Top which the
other more frequent Girders at the Distance
of every five Foot do in the Middle, where
smaller Stones are allow'd; but in these other
Girders, which we call Cornices, as they are
fewer and of more Importance, so much the
larger and the stronger Stones they require. In
both according to their different Offices, the
best, the longest, and the thickest Stones are
necessary. The smaller Girders are made to
answer to the Rule and Plum-line with the
rest of the Shell of the Wall: but these great
ones, like a Crown, project somewhat forwards.
These long, thick Stones must be laid exactly
plum, and be well link'd with the under
Courses, so as to make a Kind of Pavement
at Top to shadow and protect the Substruc

ture. The Way of placing these Stones one
upon the other, is to let the Middle of the
Stone above answer exactly to the Juncture of
the two in the Course below, so that its Weight
is equally pois'd upon them both; as (A.)
Which way of Working, as it ought not in
deed to be neglected in any Part of the Wall,
ought to be particularly followed in the Gir
ders. I have observed that the Ancients in
their checquer'd Works used to make their
Girders of five Courses of Bricks, or at least of
three, and that all of them, or at least one
Course was of Stone, not thicker than the rest,
but longer and broader; as (B.) But in their
ordinary Sort of Brick-work, I find they were
content for Girders to make at every five Foot
a Course of Bricks two Foot thick as (C)

I KNOW some too have interspers'd Plates or
Cramps of Lead of a considerable Length,
and as broad as the Wall was thick, in order
to bind the Work. But when they built with
very large Stone, I find they were contented
with fewer Girders, or even only with the
Cornices. In making the Cornices, which are
to girt in the Wall with the strongest Liga
ture, we ought to neglect none of the Rules
which we have laid down about the Girders;
namely, we should use in them none but the
longest, thickest, and strongest Stones, which
we should put together in the most exact and
regular Order, each laid nicely even and level
by the Square and Plum-line. And we ought
to be more diligent and careful in this Part of
the Work, because it is to gird in the Whole
Wall, which is more apt to ruinate in this Part
than in any other. The Covering too has its
Office with relation to the Wall; whence it
is laid down as a Rule, that to a Wall of crude
Bricks we are to make a Cornice of baked
ones, to the Intent that if any Water should
chance to fall from the End of the Covering,
or from the Gutters, it may be it may do no
Mischief, but that the Wall may be defended
by the Projecting of the Cornice. For which
Reason we ought to take Care that every Part
of the Wall have a Cornice over it for a
Covering to it, which ought to be firmly
wrought and well stucco'd over to repel all the
Injuries of the Weather. We are here again
to consider in what Manner we are to unite
and consolidate a Number of seperate Stones
into one Body of Wall; and the principal
Thing that offers itself to our Thoughts as
necessary, is good Lime; though I do not
take it to be the proper Cement for every Sort
of Stone: Marble, for Instance, if touch'd
with Lime, will not only loose its Whiteness,
but will contract foul bloody Spots. But Mar
ble, is so delicate and so coy of its Whiteness,
that it will hardly bear the Touch of any
Thing but itself; it disdains Smoke; smear'd