SLATE AND GRANITE BEAMS.
These are plentifully found in all the enclosures. Sections and splinters of slate beams are found in entrances which have portcullis grooves, one still standing in position 8 ft. above the floor. Slate beams used as entrance posts in portcullis grooves were erected before the building of the entrance, as the enclosing blocks follow the irregularities of the beams. Wood posts found in some portcullis grooves in poorer built walls are not considered ancient, and their comparative modernity is testified to by experienced builders who have very recently examined a collection of such posts. Mopani hard wood and mahobohobo have not been used in all such instances, some of the posts being of soft wood. Wooden posts have not so far been found in well-built entrances. The posts outside the clay huts of old Makalanga are older in appearance and condition than the majority of the posts found in the poorer entrances, though they very closely resemble one another in measurements and in the wood used. In one instance the groove was too large for the wooden post which had been wedged in with granite splinters, the granite being only slightly weathered.
Slate and granite beams were also employed for the bonds and ties of walls, also for ties in sharply curved walls, also for supporting the roofs over covered passages.
The nearest point to the slate formation is seven miles in a north-easterly direction. It is believed that the long granite beams were brought from the Lumbo Rocks, one and three-quarter miles to the south, where a great quantity of exactly similar shaped beams are to be seen lying scattered round the high perpendicular column of granite, the sides of which split off into the shape of the long monoliths found on the Acropolis.