22 BUREAU OF AMERICAN ETHNOLOGY [bcll. 71 



probability, the greater part of the central portion of the site, necessi- 

 tated tearing down the top of all the walls of Eooms I- VI. The 

 walls widen out in some places at the sides of a doorway. (See the 

 door from Room I to Room II, pi, 4, &.) This is a common feature 

 at Teotihuacan. The sloping walls in the rooms, a feature very com- 

 mon at Teotihuacan, is found here only at one place. Room IX on 

 the northern side of the northern wall. An overhang in the wall, 

 found also at Teotihuacan, is seen here in the northeastern corner 

 of Room IX (pi. 8, d). Adobe is almost exclusively used in the con- 

 struction of the pillars to support the roof. These adobe supports 

 are very common at Teotihuacan. The size of the adobe bricks seems 

 to vary from 0.3 to 0.7 m. long and about 0.1 m. thick. In a few 

 cases adobes were found 0.88 m. long. 



Earthen walls. — The greater number of walls in the Southern 

 Extension (Rooms VII-XI) and Northern Extension (Room XIII) 

 seems to have been built simply of earth with a layer of plaster as a 

 facing. 



Tepetate (from tetl, "stone," and petlafl, "mat"), a geological 

 formation formed by the leaching out of the surface and a redeposit 

 farther down, is used very often in the construction of the walls, and 

 in a few cases as the foundation for floors. It is found in thick beds 

 only a short distance from the site. It is still used for walls by the 

 present inhabitants. When first uncovered it is comparatively soft 

 and is cut into blocks by saws. On exposure to the air it hardens 

 quickly and is very durable. 



No walls were found in place over 1.2 m. in height. It is evi- 

 dent that the upper portions of the walls were destroyed in the 

 rebuilding. Several explorers at San Juan Teotihuacan mention 

 the fact that the walls remaining consist only of the lower portions. 



Floors. — These present much variety in their construction. The 

 best floors are often of hard cement 0.1 to 0.2 m. in thickness. Floor 

 A is an example of this kind. In other cases the floor is made of a 

 very thin layer of plaster over adobe bricks. These floors are most 

 perishable and seem to have been renewed from time to time. The 

 floors of Rooms I and II are of this type. One of the lowest floors 

 (P) is very uneven and made of a mixture of plaster and tepetate. 

 This makes a very hard and very durable substance. 



The floors are built at many different levels. In many cases a floor 

 suddenly ends with no signs of a wall bordering it and another 

 begins at a lower level. Floors run under floors at several different 

 levels. The distance between floors is often less than 0.1 m. There 

 are often sudden breaks in the floor which are difficult to explain. 

 There is an even break around the floor of Room I (pi. 4, h) which 

 illustrates this point. 



