Of all the materials put in use by the inhabitants of Mesopotamia, clay was the first and by far the most important. Clay furnished the sun-dried bricks of which the great buildings were constructed, the burnt bricks with which the artificial mounds on which those buildings stood were cased, and the enamelled bricks that enabled certain parts to be covered with a rich polychromatic decoration. The figures of the gods and demons they worshipped and the tombs into which they were thrust after death were both made of this same material. It was upon clay that they learnt to write; it was to slabs of terra-cotta that their kings confided the memory of their victories and acts of devotion, and the private population their engagements and the contracts into which they entered. For thousands of years tablets of clay thus received not only long texts, but those impressions from seals, each one of which represents a signature. While wet and soft, clay readily accepted any symbol that man chose to place upon it; once it was burnt, those symbols became practically indestructible. Accustomed to employ the unrivalled docility of kneaded earth in so many ways, the Chaldæans must, at a very early date, have used it for domestic purposes, for cooking, for holding grain, fruits, and liquids. Like every one else they must have begun by shaping such utensils with their fingers and drying them in the sun. Few remains of these early attempts have been preserved. The invention of the potter’s wheel and firing-oven must have taken place at a very remote period both in Egypt and Chaldæa. The oldest vases found in the country, those taken from tombs at Warka and Mugheir, have been burnt in the oven. Some, however, do not seem to have been ‘thrown’ on the wheel. The thickness of their walls and their irregular shape suggest that the potter fashioned them with the back and palm of his hand (Figs. 163–165). The paste is coarse; it is mixed with chopped straw, which shows here and there on the surface; there is neither ornament nor glaze, and the curves are without grace.[361] [Illustration: FIGS. 163–165.--Chaldæan vases of the first period. British Museum.] [Illustration: FIGS. 166–168.--Chaldæan vases of the second period. British Museum.] Some other vases found in the same cemeteries are ascribed to a later epoch. They give evidence of a real progress in art. We have already figured two examples in our first volume (Figs. 159 and 160); three more are given in Figs. 166–168. The body is finer, and sometimes covered with a slight glaze; there is still no decoration, but the forms are obviously meant, and not without distinction. These objects have been thrown on the wheel, and the dexterity of their maker is further shown by the skill with which their handles are attached. [Illustration: FIG. 169.--Chaldæan vase, about 4 inches high. British Museum.]