ackwards the whole length of the interior
splay of the window, and, from the marks upon them, have evidently been
hammer-dressed.[53] Internally, in this eastern gable, there is placed
below the window, and in continuation of its interior splay, a recess
about 18 inches in depth, and of nearly the same breadth as the
divergence of the jambs of the window. The broken base or floor of this
recess is in the position of the altar-stone in some small early Irish
chapels.

The accompanying sketch (see woodcut, Fig. 7) of the exterior of the
eastern gable shows that the stones of which it is built have been
prepared and dressed with sufficient care--especially those forming the
angles--to entitle us to speak of it as presenting the type of rude
ashlar-work. The stones composing it, particularly above the line of the
window, are laid in pretty regular horizontal courses; lower down they
are not by any means so equable in size. The masonry of the side walls
is much less regular, and more of a ruble character. The walls are on an
average about 3 feet in thickness.[54] The stones of which the building
is composed are, with a few exceptions, almost all squared sandstone.
The exceptions consist of some larger stones of trap or basalt, placed
principally along the base of the walls. Both secondary trap and
sandstone are found _in situ_ among the rocks of the island. A roundish
basalt stone, 2 feet long, forms a portion of the floor of the building
at its southern corner. At other points there is evidence of a
well-laid earth floor. The whole interior of the building has been
carefully plastered at one time. The surface of this plaster-covering of
the walls, wherever it is left, is so dense and hard as to be scratched
with difficulty. The lime used for building and cementing the walls, as
shown in a part at the west end which has been lately exposed, contains
oyster and other smaller sea-shells, and is as firm and hard as some
forms of concrete.

I have reserved till the last a notice of one of the most remarkable
architectural features in this little building, namely, its arched or
vaulted stone roof,--the circumstance, no doubt, to which the whole
structure owes its past durability and present existence.

Stone roofs are found in some old Irish buildings, formed on the
principle of the horizontal arch, or by each layer of stone overlapping
and projecting within the layer placed below it till a single stone
closes the top. A remar