ent are
made use of to make the Eaves of Houses; over these Reeds must be laid a
Plaster of Mortar, made of Sand, to hinder the Drops of Water which may
fall from above from endamaging these _Plat-Fonds_. After which, the
under part must be Plaster'd pretty thick, making all Places equal with
Mortar made of Lime and Sand, that it may be afterwards Polished with
Mortar made with Lime and Marble.

[Sidenote: _Lib. 5. Chap. 10._]

The Ancients sometimes made double Vaults, when they were afraid that
the Humidity which is engender'd, by the Vapours which mount up might
rot the Wood which is upon the Vaults. This Method they principally made
use of in their Baths.

The _Corniches_ which are made use of under the _Plat-Fonds_, ought to
be little, lest their great Jetting out, or Projecture should make them
heavy, and apt to fall. For this Reason they ought to be made of pure
Stuck of Marble, without any Plaster, that all the Work drying at the
same time, may be less apt to break.

ART. VI.

_Of Plastering_.

To make Plaster that it may continue a long time, and not crack; you
must take Care to lay it on Walls that are very Dry; for if the Walls be
Moist, the Plastering being expos'd to the Air, and drying faster than
the Walls, will crack.

To do this Methodically, it must be laid, Bed after Bed, or Lay after
Lay, having a great Care not to lay one Bed till the other be almost
dry. The Ancients put six Lays, three of Mortar made of Lime and Sand,
and three of Stuck. The first Lays or Beds were always thicker than the
last, and they were very careful to make use of no Mortar made either of
Sand or Stuck in their Plastring, that had not been a long time beaten
and mix'd together; especially the Stuck, which must be beaten and mix'd
till it will not stick to the Trowel.

They took likewise a great deal of Pains to run several times over and
beat the Plaster, which gave it a Hardness, a Whiteness, and Polish'd it
so well, that it shin'd like a Mirror.

These Plasterings so made, serve to Paint in _Fresco_ upon; for the
Colours being laid upon the Mortar before it was dry, pierced it, and
Embodied with it; so that the Painting could not be defaced though it
were wash'd; which would easily be wash'd off if the Mortar were dry.

They likewise laid these Plasterings upon Partitions of Wood filled with
fat Earth, nailing Reeds to them, as we do Laths, and daubing it over
with Clay, and then putting on another row of R