place which was left void is fill'd up with Mortar and Pebbles
thrown in together; after this they bind the Stones of one _Parement_
or _Course_ to those of another with Cramp-Irons fasten'd with melted
Lead. This is done to the end, that the abundance of Mortar which is in
the middle may furnish and communicate a sufficient Humidity to the
Joints of the great Stones which make the _Parements_. See the Figure K.
Table I.

There are many Precautions to be given to make the Masonry more firm and
durable, and these Precautions are common to all the different sorts of
Masonry.

[Sidenote: _Lib. 1. Chap. 5._]

When you would have the Walls very thick, for great and heavy Buildings,
you must strengthen the inner part of the Wall with long Piles of singed
Olive, which serves for Keys and Braces, for this Wood being so prepar'd
never corrupts.

[Sidenote: _Lib. 6. Chap. 11._]

[Sidenote: _Vide Index._]

It is likewise of great Importance for the strength of Walls, that all
be directly Perpendicular, and that the _Chains_, the _Pillars_ and
_Pieds-droits_ or _Piers_ be so situated, that _solid_ always answer'd
to the _solid_; for if there be any part of the Wall or any Pillar that
carrys false, it is impossible the Work should continue long.

There are also two ways of strengthning the Walls, which are either to
ease them of their own weight, or of that of the Earth which they are to
support.

The first way of easing is in those Places where there are void spaces,
as above Doors or Windows. These easements may be made two different
ways; the first is to put over the Lintel which supports the Wall, which
is over the void space of the Gates and Windows, two Beams, which lying
or resting below directly upon _Pieds-droits_ or _Piers_ meet together
above.

The other way is, to make directly over the void spaces Vaulted Arches
with Stones cut corner-ways and tending to one Center. For the Walls be
so strengthned by the means of these easements, that part of the Wall
which is below will not sink at all being easied of the load of the part
that is above, and if some defect should happen by tract of time, it
may be mended without propping that which is above.

The second way of easing, is, for Walls that are made to support the
Earth; for, besides the extraordinary thickness which they ought to
have, they should have likewise Buttresses on that side next the Earth,
so far distant one from another as is the breadth of the Wal