8The different species of walls are, the RETICULATUM (net-like), a method now in general use, and the INCERTUM (uncertain), which is the antient mode. The reticulatum is the most beautiful, but is very liable to split, from the beds of the stones being unstable, and its deficiency in respect of bond. The incertum, on the contrary, course over course, and the whole bonded together, does not present so beautiful an appearance, though stronger than the reticulatum.
8There are two styles of walls: “opus reticulatum,” now used by everybody, and the ancient style called “opus incertum.” Of these, the reticulatum looks better, but its construction makes it likely to crack, because its beds and builds spread out in every direction. On the other hand, in the opus incertum, the rubble, lying in courses and imbricated, makes a wall which, though not beautiful, is stronger than the reticulatum.