Unburnt brick were never regarded by the inhabitants of Mesopotamia as a safe building material, and experience demonstrated the necessity of supplementing with huge but tresses the buildings in which the material was employed, and it is probable from the evidence of those who have explored these ruins that the supplemental supports were more thoroughly and carefully constructed than the buildings, the walls of which they were intended to sustain. The crude brick walls of Chaldean buildings were perforated with numerous ventilating tunnels, through which the warm air could penetrate, and thus dissipate any moisture that might be contained in the brick. Perfora tions of this kind have been discovered in the ruins of Babylon and also in other Chaldean cities ; but in Assyria no such open ings of the kind which we have described for the admission of air have been found. It is the almost unanimous opinion of explorers that sun-dried brick were never left unprotected in Mesopotamia, the material being commonly protected by a thin coat of stucco. It is stated by M. Place, that at Nineveh this stucco was formed by a mixture of burned chalk and plaster, the compound producing a sort of white gum, which adhered intimately to the clay wall. It is probable that many buildings had no outward ornament beyond that imparted by the brilliant whiteness of this stucco, the effect of which is still to be seen even at the present time in the whitewashed houses of the East.
The great perfection to which the ancients carried the art of brick-making is probably due to the abundance of labor, plenty of time to devote to each stage of the work, their great patience and painstaking, and the natural drying and preserving climate of the East. The dry, warm atmospheres of Egypt, Assyria and Babylonia, which countries were the nurseries of the ceramic arts, have kept in a good state of preservation for more than three thousand years the sun-dried brick so common in those countries ; many well-preservad adobes are also found in towns and walls of ancient India.
Brick, burned and unburned, were employed in the con struction of the Great Wall of China, which is the most remark able fortification ever erected by human hands ; millions of men were employed for the space of ten years in its construction, and it was completed in 21[1 B. C. The length was about 125o miles, the height averaging about 22 feet ; each face of the wall was built of hewn stone or brick, and filled in between with earth ; it was wider at the bottom than at the top, which was sufficiently wide for six horsemen to ride abreast ; it was built by the great Emperor of China, Shee-Hoang-Ti, who is the national hero.
In Spain the use of sun-dried brick has more or less con tinued in some portions even to the present day. In Mexico,
sun-dried brick have been continuously employed for many centuries, and the early Spanish-American buildings in Cali fornia were commonly constructed of adobes. The exterior walls of the buildings in Mexico and the Spanish-American buildings in California were often covered with a bluish stucco or enamel, which was sometimes applied after the erection of a building or sometimes before. In the southern portion of Texas, adobes are still often used for the construction of dwell ings. In the southern portion of the State of Kansas, which is often visited with wind storms which destroy frame structures, adobes are often employed for buildings ; the walls are com monly carried up to the height of one story, and the roof has a steep pitch and extends about two feet six inches beyond the faces of the walls. The steep roofs give a half story or attic in the upper portion of the dwelling, and the wide projecting eaves protect the walls. The adobes are made about eighteen inches square and four inches thick, and half brick to correspond. These sun-dried brick, as were those of old, are sometimes made with straw and sometimes without. Buildings constructed of adobes are termed, in the Western States, " dobies," and in Mexico, Texas, Colorado, New Mexico, and Arizona, buildings so constructed are called "adobe houses." It is probable that burned clay did not find great favor with the ancient Greeks, as they possessed an abundance of stone.
The walls of Athens, on the side towards Mount Hymettus, were built of brick, and this is probably the largest undertak ing in which they were employed by the Greeks.
The use of brick for architectural construction was never, at any period, extensive in Greece, but in some few cases they were employed in minor public edifices. Their first applica tion has been attributed to Hyperbius, of Crete, and Euryalus or Ayrolas. The brick were made with a mould, and were named after the number of palms' lengths.
In the first century of the Christian era, while the brick made by the Romans were of a superior quality, those made by the Greeks were very inferior.
But little is known of the material used in the early buildings of the Latin cities ; yet, judging from the great extent and destructiveness of the fires in Rome, it is inferred that wood entered largely into the construction of buildings up to the time of Nero. During his reign, in A. D. 64, two-thirds of the city was destroyed by fire. Augustus, who devoted so much time and thought to beautifying Rome, had restricted the height of buildings to seventy feet, but this height was still further curtailed by Nero after the conflagration, and in the re building a certain portion of the houses were constructed of a fire-proof stone from Gabii and Alba.