In ancient construction, the method of arranging the material varied somewhat. In some cases series 3 was very carefully constructed of straight willow wands laid side by side in contact. This gave a very neat appearance to the ceiling within the room. Examples were seen in Canyon de Chelly, at Mummy Cave, and at Hungo Pavie and Pueblo Bonito on the Chaco. [Illustration: Plate LXXI. Pescado houses.] Again examples occur where series 2 is composed of 2-inch poles in contact and the joints are chinked on the upper side with small stones to prevent the earth from sifting through. This arrangement was seen in a small cluster on the canyon bottom on the de Chelly. The small size of available roofing rafters has at Tusayan brought about a construction of clumsy piers of masonry in a few of the larger rooms, which support the ends of two sets of main girders, and these in turn carry series 1, or the main ceiling beams of the roof. The girders are generally double, an arrangement that has been often employed in ancient times, as many examples occur among the ruins. The purpose of such arrangement may have been to admit of the abutment of the ends of series 1, when the members of the latter were laid in contact. In the absence of squared beams, which seem never to have been used in the old work, this abutment could only be securely accomplished by the use of double girders, as suggested in the following diagram, Fig. 38. [Illustration: Fig. 38. Showing abutment of smaller roof beams over round girders.] The final roof covering, composed of clay, is usually laid on very carefully and firmly, and, when the surface is unbroken, answers fairly well as a watershed. A slight slope or fall is given to the roof. This roof subserves every purpose of a front yard to the rooms that open upon it, and seems to be used exactly like the ground itself. Sheepskins are stretched and pegged out upon it for tanning or drying, and the characteristic Zuñi dome-shaped oven is frequently built upon it. In Zuñi generally upper rooms are provided only with a mud floor, although occasionally the method of paving with large thin slabs of stone is adopted. These are often somewhat irregular in form, the object being to have them as large as possible, so that considerable ingenuity is often displayed in selecting the pieces and in joining the irregular edges. This arrangement, similar to that of the kiva floors of Tusayan, is occasionally met with in the kivas. In making excavations at Kin-tiel, the floor of the ground room in which the circular door illustrated in Pl. C, was found was paved with large, irregular fragments of stone, the thickness of which did not average more than an inch. Its floor, whose paving was all in place, was strewn with broken, irregular fragments similar in character, which must have been used as the flooring of an upper chamber. WALL COPINGS AND ROOF DRAINS.