The Digital Ark: Early Modern Collections of Curiosities in England and Scotland, 1580-1700
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References in Documents:Architecture. A Geometrick
FLAT FLOOR.
Given by the
neated (a) by Dr. Geometry at
Who was pleas'd to give me the following
Account, as an
Abstract of that he hath formerly published hereof.
(a)
a) See his
Book
tu, Cap. 6.
Prop. 10.
Fig. 243
I did first, saith the Doctor, Contrive and Delineate It in
the
Year, 1644. at
afterwards I was made Professor of Geometry at
about the Year, 1650. I caused it
to be framed of small
pieces of Wood,
representing so many pieces of Timber;
prepar'd by Mr. Joyner in
ther by my self.
This I shewed soon after to divers in
larly to Dr.
Warden of
another to be made for himself,
according to that Pattern.
Which he kept by him for many years,
and afterwards pre
sented to the
After the Restauration, I caus'd another to be
made;
and, in the Year, 1660. presented it to
who was well pleas'd with it, and caused
it to be reposited in
his Closet.
On the Model first mention'd, I Read two Publique
Lectures at Vespers
of the Publique Act: the
one, in the Year,
1652. as to the Construction of it; the
other, in the Year, 1653.
as to the computation of what
weight every Joynt of it sustains;
whereby it might be the
better judged how far it may be safely
practised. The
greatest weight charged on any one Joynt, doth not
amount to Ten-times the weight of one Beam: And the
greatest
weight bor'n by any one Beam; not to seventeen
times its own
weight: and even this, not laid all on the
same part, but
distributed to several parts of it. The sum
of these two Lectures, is to be seen in the Sixth Chapter of
my Book
A Third Lecture, much to the same purpose, I read,
May, 1699
Duke of
Visit,
and me with his Presence at that Lecture. After
which, he was pleased very particularly to consider both
the
Delineation and Model, and declared himself very well
pleased with
it,
The contrivance is obvious to the Eye. The outsides re
present the Walls of the Building on which this Flat Floor
or
Roof is to be laid. The Beams next adjoyning to the
sides, have
one end lodged on those Walls; the other end
sustained by another
Beam, lying cross; both ends of
which, are in like manner
sustained by other cross Beams;
and those again by others; till
they reach the other Walls.
So that no one of them can fall,
unless the Walls fail, or the
Beams break: all mutually sustaining
each other without
any Pillar or Prop to support them, besides the
outer
Walls.
The Models I caused to be made, and that of the
Society
as much as the Length of
the longest Beam. But may be
continu'd, at pleasure, to farther
breadth, as shall be thought
fit. With this Caution: That the
farther the Work is
continu'd, the greater Weight will be charged
on every
Joynt; especially near the middle. And though in this
Model, no one Beam is charged with so much as seventeen
times its own weight: yet if the Work be continu'd to a
greater
breadth, the proportional Weight will be thereby
increased. And
therefore must be limited, according to
the strength of Timber,
able to bear more or fewer times
its own weight.
I do not know, that yet it hath been reduced to practise,
in more
than four Pieces, in this Form. Such is
one of the Floors in the
Tower of the Publique
Schools at
Length of the Beams, is as three to two. But
may doubtless be continu'd much further: especially in
such a Roof
or Floor, as is not to bear much more than its
own weight.
Thus, for instance, a Bowling-Green of near an
Acre of
Ground, may be cover'd with a Frame of long slender
Vines, or other like Plants to run upon, so as to shade the
whole.
Note here, That whereas the ends of the several pieces
are to lie
upon those that cross them, about the middle
thereof; it will be
necessary at every Joynt to abate both
pieces half way, or near
it; that one may be thus let into
the other, and the whole reduced
to a Flat. But whether
such piece, so abated doth end even with
that on which it
lies, or doth lie over somewhat beyond it; is
indifferent.
And though That may seem more elegant; This, perhaps,
may be fitter for use.
Each piece, I say, must be so abated half way, or near
it. For,
whereas those Beams, especially if of a considera
ble
length, will, with the weight, bow a little; if this abate
ment be somewhat less than half way, (whereby without
such
bowing, the whole would somewhat rise in the mid
dle) it
will by such bowing be reduced to a Flat.
Note also, That a Frame thus contriv'd, needs neither
Nail nor Pin; the several
pieces fastening, as well as support
ing one another.
Yet, if it be to bear a great weight more than
its own; it will be
convenient to fasten each Joynt with
Pins; and, if need be, to strengthen it with Iron-Plates, or
line it with other pieces
of Timber, to be fasten'd with Iron- Bolts; to make amends for what is weaken'd by the
abate
ments at the
Joynts:which will make the whole Frame
exceeding strong.