horizontal, or rather with their beds slightly inclined to the horizon, as they should properly be in a true arch. Beyond this the bricks are all on edge, with their beds vertical; this construction, however faulty in an arch of small depth transversely, as in walls, is of great strength when built of bricks cut to shape and of great depth transversely. With stone, especially sedimentary stone which has widely different strengths along and across the layers or plane of cleavage, a mode of construction which brings the line of pressures to bear not perpendicularly, but along the planes of cleavage, it is undoubtedly faulty; but in brick which is homogeneous, the construction of an arch of bricks edge to edge is positively an advantage, as the number of joints of compressible mortar is lessened by the arrangement; the only drawback, lateral weakness, does not come into calculation in long tunnel vaults, which in this direction have more strength than they need.
A cornice runs along three sides of the interior of the sanctum at the springing of the tunnel vaults, but there is no cornice in the back wall; further, the side walls of the chamber are each a little over 8 feet thick, while the fourth wall is 10 feet thick, and the back wall only 6¼ feet; these circumstances, combined with the fact that bricks of three different varieties occur in the temple, show that the tunnel vault is a subsequent addition; for if we, without altering the external dimensions of the temple, make the thickness of the walls all round 6¼ feet, by enlarging the chamber inside, we shall get a square chamber 15 feet square, placed centrically as it ought to be.
The absence of a cornice, too, on the back wall internally, shows that the original building was not cut up into two storeys by the interposition of the vaulted or any roof. It is clear, therefore, that the temple, as originally built, consisted of a chamber 15 feet square, with walls 6¼ feet thick all round; subsequently the vault was added by increasing internally the thickness of the side walls by 1¾ feet nearly, and thickening the front wall by additions internally to 10 feet, thus leaving a square chamber no longer 15 feet, but only 11¼ feet square, and eccentrically placed within the structure.
The walls of the temple internally are ornamented by niches, three on each side, doubtless meant to hold lamps.
The entrance is as usual represented by a great rent or opening in the face of the tower, consisting of vertical sides,
