There are small cliff-houses in the same canyon not far from Dolores, but these are smaller and their walls very poorly preserved. An interesting feature of these cliff-houses in Lost Canyon is that they mark the northern horizon of cliff-dwellings of the Mesa Verde type, having kivas similarly constructed. GREAT HOUSES AND TOWERS Great houses and towers differ from pueblos of the pure type but may often be combined with them, forming composite houses arranged in clusters called villages. Castles and towers may be isolated structures without additional chambers, or may have many annexed rooms which are rectangular, round, or semicircular in form. Semicircular towers surrounded by concentric curved walls connected by radial partitions forming compartments are shown in Horseshoe Ruin, to which attention has been called in preceding pages, and possibly in the circular or semicircular ruins on hilltops near Dolores. MASONRY The masonry of the great house and tower type (pl. 11, _a_, _b_) varies in excellence, not only in different examples but also in different portions of the same building. Some of the walls contain some of the best-constructed masonry north of Mexico; others (see pl. 6, _b_) are crudely made. In the Great House of the Holly group, where the walls show superior construction, the lowest courses of rock are larger than those above, but in Hovenweep Castle small stones are found below those of larger size; the Round Tower in McLean Basin shows small and large stones introduced for ornamentation. The ambitious constructors of several towers have built the foundations of these towers on bowlders sloping at a considerable angle, and it is a source of wonder that these walls have stood for so many years without sliding from their bases. Although so well constructed in many instances, the courses were weak from their want of binding to the remaining wall. As a consequence many corners have fallen, leaving the remaining walls intact. The builders often failed to tie in the partitions to the outer walls, by which failure they lost a brace and have sprung away from their attachment. In a general way we may recognize masonry of two varieties. 1. That in which horizontal courses are obscure or absent. This has resulted from the use of stones of different sizes, the intervals between which are filled in with masses of adobe. These stones are little fashioned, or dressed only on one side, that forming the face of the wall.