This splendid ruin is built of a natural concrete called culeche. The external walls are rough, but are smoothly plastered within, showing the marks of human hands. Two pairs of small holes in the walls opposite others in the central room have occasioned much speculation. Two look east and west; the others, also on opposite walls, look north and south. Some persons conjecture that observations were made through them of the solstices, and perhaps of some star, to establish the seasons for these primitive people. "The foundation for this unwarranted hypothesis," Doctor Fewkes writes, "is probably a statement in a manuscript by Father Font in 1775, that the 'Prince,' 'chief' of Casa Grande, looked through openings in the east and west walls 'on the sun as it rose and set, to salute it.' The openings should not be confused with smaller holes made in the walls for placing iron rods to support the walls by contractors when the ruin was repaired." TUMACACORI NATIONAL MONUMENT One of the best-preserved ruins of one of the finest missions which Spanish priests established in the desert of the extreme south of Arizona is protected under the name of the Tumacacori National Monument. It is fifty-seven miles south of Tucson, near the Mexican border. The outlying country probably possessed a large native population. The ruins are most impressive, consisting of the walls and tower of an old church building, the walls of a mortuary chapel at the north end of the church, and a surrounding court with adobe walls six feet high. These, like all the Spanish missions, were built by Indian converts under the direction of priests, for the Spanish invaders performed no manual labor. The walls of the church are six feet thick and plastered within. The belfry and the altar-dome are of burned brick, the only example of brick construction among the early Spanish missions. There is a fine arched doorway. [Illustration: TUMACACORI MISSION] [Illustration: _From a photograph by T.H. Bate_ MONTEZUMA CASTLE] For many reasons, this splendid church is well worth a visit. It was founded and built about 1688 by Father Eusebio Francisco Kino, and was known as the Mission San Cayetano de Tumacacori. About 1769 the Franciscans assumed charge, and repaired and elaborated the structure. They maintained it for about sixty years, until the Apache Indians laid siege and finally captured it, driving out the priests and dispersing the Papagos. About 1850 it was found by Americans in its present condition. NAVAJO NATIONAL MONUMENT The boundary-line which divides Utah from Arizona divides the most gorgeous expression of the great American desert region. From the Mesa Verde National Park on the east to Zion National Monument on the west, from the Natural Bridges on the north to the Grand Canyon and the Painted Desert on the south, the country glows with golden sands and crimson mesas, a wilderness of amazing and impossible contours and indescribable charm.