712

THEORY AND PRACTICE OF ENGINEERING.

Book IX.

sequence of the great pressure that has been made use of; the clay, being more compact,dries on the outside long before the centre parts with its humidity, and in consequence thesurface is apt to peel oft*. This machine does not exercise more than a slight pressure, andthe bricks made with it are uniform in size and quality.

The Marble 'Tiles , which covered the Greek and Roman temples, have been imitated inclay, and when properly made have an elegant effect: flat tiles with raised sides extend

rig. 595.

ROHAN Til.

from rafter to rafter, the upper ends having a rib that enters a groove formed on the under-side of the tile placed above it; after these are laid, the joints in the direction of therafters are covered with other tiles, formed like the half of a frustum of a cone, and madeto lap over each other; the ends over the eaves or cornice are closed by an ornament, as aneagle, honeysuckle, or flower.

In other examples the long joints are covered by rib tiles, with a fine arris or edge at thetop, which is calculated to produce considerable strength, and keep out the weather equallywell.

fig. 596.

GREER TILES.

The architects in Paris have made use of such to cover both public and private buildings,and some of the manufacturers produce them in all their varied forms by machines of avery simple kind: those which covered the temple of Jupiter Stator at Rome were ofmarble, and of considerable dimension, and since their discovery they have served asmodels for imitation.

The Sunk Tile, with its lateral raised fillets, being laid side by side, had the upper edgeoverlapped by the succeeding course; the longitudinal joints, or those in the directionof the rafters, were covered by a rib, cut on the underside to saddle the fillets of the twotiles with the joint between them. The lower ends were covered by a perpendicular orna-mental tile or antifissa, the sculpture of which constantly varied : on some of those at theTemple of Vesta at Rome , which the writer discovered, is the representation of an eagle,and on others the honeysuckle.

In Flanders, where moulding in clay was at a very early period carried to great perfec-tion, are many varieties of pattern ; and they are contrived not only to produce a goodeffect as they lie, but to keep out the weather: the wavy, which is the most common,are laid on or taken off with very little trouble; they are made with a projecting knob