The exterior walls rise to a height of from 20 to 25 feet above the ground. This height accommodated two stories, but the top of the wall is from 1 to 2 feet higher than the roof level of the second story. The middle room or space was built up three stories high, and the walls are still standing to a height of 28 to 30 feet above the ground level. The tops of the walls, while rough and greatly eroded, are approximately level. The exterior surface of the walls is rough, as shown in the illustrations, but the interior walls of the rooms are finished with a remarkable degree of smoothness, so much so that it has attracted the attention of everyone who has visited the ruin. Plate CXV shows this feature. At the ground level the exterior wall is from 31/2 to 41/2 feet thick, and in one place over 5 feet thick. The interior walls are from 3 to 4 feet thick. At the tops the walls are about 2 feet thick. The building was constructed by crude methods, thoroughly aboriginal in character, and there is no uniformity in its measurements. The walls, even in the same room, are not of even thickness; the floor joists were seldom in a straight line, and measurements made at similar places (for example, at the two ends of a room) seldom agree. Casa Grande is often referred to as an adobe structure, but this use of the term is misleading. Adobe construction consists of the use of molded brick, dried in the sun, but not baked. The walls here are composed of huge blocks of rammed earth, 3 to 5 feet long, 2 feet high and 3 to 4 feet thick. These blocks were not molded and then laid in the wall, but were manufactured in place. Plate CXVI shows the character of these blocks. The material employed was admirably suited for the purpose, being when dry almost as hard as sandstone and nearly as durable. A building with walls of this material would last indefinitely, provided a few slight repairs were made at the conclusion of each rainy season. When abandoned, however, sapping at the ground level would commence and would in time bring down all the walls; yet in the two centuries which have elapsed since Padre Kino's visit to this place--and Casa Grande was then a ruin--there has been but little destruction from the elements, the damage done by relic hunters during the last twenty years being, in fact, much greater than that due to all causes in the preceding two centuries. The building was well provided with doorways and other openings, arranged in pairs, one above the other. There were doorways from each room into every adjoining room, except that the rooms of the middle tier were entered only from the east. Some of the openings were not used, and were closed with blocks of solid masonry, built into them long prior to the final abandonment of the structure. CONDITION OF CASA GRANDE IN 1891