The dormitory wing constructed of adobe has been greatly altered. Early drawings indicated that the windows and doors were originally arched. Especially notable is the roof over the dormitory and adjoining loggia. Except for the outer covering of tile its structure has never been disturbed. It is supported on heavy beams of mesquite timber and, as was the general custom, the beams were covered with stalks of ocotillo, leaves and reeds, the cracks then filled with soft adobe, the whole finally forming a solidly reinforced roof. The north wing of the dormitory, although entirely new, harmonizes with the earlier structure. Engineers are working to bring back into line the massive walls of the mission and plan to reinforce the dome and portions of the fine facade which have recently fallen away. Secret processes used in painting the murals are being utilized in restoring the walls of the structure. This process, recently discovered through research at the Smithsonian Institution, solves a problem artists have been attempting for years to achieve through the use of oil paint. The root of the ocotillo plant supplies the red. The pulpy sap of the saguaro (giant) cactus gives the blue. Brown and yellow are made from the first layer of skin under the bark of the palo verde tree, and green comes from sage leaves while mesquite beans make the thick black. The degree of boiling gives the shades desired. The preservation of San Xavier del Bac is a worthy gesture in enabling increasing thousands to see intact this magnificent example of early mission architecture. Bibliography Bancroft, Hubert Howe. _History of Arizona and New Mexico._ San Francisco, The History Company, 1889. Vol. 17 of his _History of the Pacific States of North America_. Bolton, Herbert Eugene. _Kino’s Historical Memoir of Pimería Alta._ Cleveland, Arthur H. Clark Company, 1919. 2 v. ——, _Rim of Christendom_. New York, Macmillan, 1936. ——, _Padre on Horseback_. San Francisco, Sonora Press, 1932. Bonaventure, Father, O.F.M. _Mission San Xavier del Bac._ Topawa, Ariz., Franciscan Fathers of Arizona, San Solano Missions. Duell, Prent. _Mission Architecture Exemplified in San Xavier del Bac._ Tucson, Arizona Archaeological and Historical Society, 1919. Engelhardt, Father Zephyrin. _The Franciscans in Arizona._ Harbor Springs, Mich., Holy Childhood Indian School, 1899. Hallenbeck, Cleve. _Spanish Missions of the Old Southwest._ New York, Doubleday, Page & Company, 1926. Hinton, R. J. _Handbook to Arizona._ New York, Payot, Upham & Company, 1878. Lockwood, Frank C. _With Padre Kino on the Trail._ Tucson, University of Arizona, 1934. Lummis, Charles F. _The Spanish Pioneers._ Chicago, A. C. McClurg & Company, 1914. Lutrell, Estelle. _The Mission of San Xavier del Bac._ Tucson, Acme Press, 1934.