The Repair of Casa Grande Ruin, Arizona, in 1891 | Page 3

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 3? to 4? 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
The south and east fronts of Casa Grande seem to have suffered, particularly from the weather, and here rainstorms have probably caused some of the damage. The outer faces of the walls are of the same material as the wall mass, all the masonry being composed of earth from the immediate site. In the construction of the walls this soil was laid up in successive courses of varying thickness, whose limits form clearly defined and approximately horizontal joints. The northeast and southeast corners of the building have entirely fallen away, and low mounds of their debris still show many knobs and lumps, parts of the original wall mass.
The destruction of the walls was due mainly to undermining at the ground level. The character of this undermining is shown in many of the illustrations to this report, especially in plate CXVI, and its extent is indicated on the accompanying ground plan (plate CXVII) by dotted lines within the wall mass. Although the material of which the walls are composed is very hard when dry, and capable of resisting the destructive influences to which it has been subjected for a long time, yet under certain conditions it becomes more yielding. The excessively dry climate of this region, which in one respect has made the preservation of the ruin possible, has also furnished, in its periodic sandstorms, a most efficient agent of destruction. The amount of moisture in the soil is so small as scarcely to be detected, but what there is in the soil next to the walls is absorbed by the latter, rising doubtless by capillary attraction to a height of a foot or more from the ground. This portion of the wall being then more moist than the remainder, although possibly only in an infinitesimal degree, is more subject to erosion by flying sand in the windstorms so frequent in this region, and gradually the base of the wall is eaten away until the support becomes insufficient and the wall falls