were dressed more or less carefully, according to the positions they were to occupy.  When the walls were of medium thickness, as in most partition walls, they are well wrought on all sides.  When the wall was thick, the core blocks were roughed out as nearly cubic as might be, and piled together without much care, the hollows being filled up with smaller flakes, pebbles, or mortar.  Casing stones were carefully wrought on the faces, and the joints dressed for two-thirds or three-quarters of the length, the rest being merely picked with a point (Note 6).  The largest blocks were reserved for the lower parts of the building; and this precaution was the more necessary because the architects of Pharaonic times sank the foundations of their temples no deeper than those of their houses.  At Karnak, they are not carried lower than from 7 to 10 feet; at Luxor, on the side anciently washed by the river, three courses of masonry, each measuring about 2-1/2 feet in depth, form a great platform on which the walls rest; while at the Ramesseum, the brickwork bed on which the colonnade stands does not seem to be more than 10 feet deep.  These are but slight depths for the foundations of such great buildings, but the experience of ages proves that they are sufficient.  The hard and compact humus of which the soil of the Nile valley is composed, contracts every year after the subsidence of the inundation, and thus becomes almost incompressible.  As the building progressed, the weight of the superincumbent masonry gradually became greater, till the maximum of pressure was attained, and a solid basis secured.  Wherever I have bared the foundations of the walls, I can testify that they have not shifted.

[Illustration:  Fig. 52.—­Masonry in temple of Seti I. at Abydos.]

The system of construction in force among the ancient Egyptians resembles in many respects that of the Greeks.  The stones are often placed together with dry joints, and without the employment of any binding contrivance, the masons relying on the mere weight of the materials to keep them in place.  Sometimes they are held together by metal cramps, or sometimes—­as in the temple of Seti I., at Abydos—­by dovetails of sycamore wood bearing the cartouche of the founder.  Most commonly, they are united by a mortar-joint, more or less thick.  All the mortars of which I have collected samples are thus far of three kinds:  the first is white, and easily reduced to an impalpable powder, being of lime only; the others are grey, and rough to the touch, being mixtures of lime and sand; while some are of a reddish colour, owing to the pounded brick powder with which they are mixed.  A judicious use of these various methods enabled the Egyptians to rival the Greeks in their treatment of regular courses, equal blocks, and upright joints in alternate bond.  If they did not always work equally well, their shortcomings must be charged to the imperfect mechanical means at their disposal.  The enclosure walls, partitions, and secondary facades