Among the larger rectangular clay tablets in existence are those containing syllabaries. Owing to the deterioration and simplification which the cuneiform characters underwent in the course of ages, the Assyrian scribes found it necessary to make lists of the early Babylonian characters adding what they believed to be the later Assyrian equivalents. Most of these syllabaries consist of three columns; in the middle column the Assyrian sign to be explained is given, on the left the Sumerian value of the same, and in the right-hand column either the Assyrian name for the sign, or else the Assyrian meaning, and occasionally both. These syllabaries are obviously of immense importance in the reconstruction of the old Sumerian language. Other tablets of abnormally large size are those dealing with astrology, magic and medicine: the two latter subjects are inextricably confused owing to the fact that they went hand in hand with each other; the medicine was prescribed and administered, but the medicine alone was by no means sufficient to cure the patient, that could only be effected by the potent spell of the magician. But the largest clay tablets emanate from Babylonia and contain lists of accounts mostly concerning grain, cattle, asses, lambs, sheep. Some of these tablets are perfectly square, and measure as much as a foot each way, while nearly all of them are more square than oblong: the clay of which they are made is of fine quality, and the Babylonian characters with which they are inscribed are singularly clear. Most of them may be assigned to the second half of the third millennium B.C., and many of them are specifically dated in the reign of Dungi, king of Ur about 2400 B.C. But as already mentioned, tablets were not always rectangular; sometimes they assumed a circular form. Tablets of this kind are usually inscribed in the Sumerian language, and contain lists of landed estates and fields, with information regarding their size, their capacity for producing crops and other details. Many of these circular tablets are dated, the year deriving its name after some noteworthy event, as was the regular mode of dating in the early days of Babylonian civilization. Thus many of these lists are dated “in the year after that in which the land of Khukhnuri was laid waste,” and were drawn up in the reign of Bur-Sin and other kings of Ur, i.e. during the second half of the third millennium B.C. The clay of which these tablets are made is of the finest, while the writing is exceedingly clear; they vary from about two to six inches in diameter, and are oval on one side and more or less flat on the other.