The Register itself, as well as the office for its maintenance and for pensionary account, was called the DEWÂN or Department of the Exchequer. The State had by this time, as we have seen, an income swollen by the tribute of conquered cities, the poll-tax of subjugated peoples, the land and other regular assessments, the spoil of war, and the tithes. The first charge was for the revenue and civil administration; the next for military requirements, which began soon to assume a sustained and permanent form; the surplus remained (as has been now set forth) for pensionary and eleemosynary distribution. The whole revenues of Islam were thus expended as soon, almost, as received; and Omar took a special pride in seeing the treasury, in accord with this principle, emptied to the last dirhem.[354] The accounts of the various provinces were at the first kept by natives of the country in the character to which they were accustomed--in Syria by Greeks, and in Irâc by Persians. At Kûfa the use of Pehlevi was maintained till the time of Hajjâj, when, an Arab assistant having learned the art from the chief treasurer, the Arabic system of record and notation was introduced. [Sidenote: Vast extent of Arab exodus.] We are not told the numerical result of the Dewân of Omar, but the population of Kûfa and Bussora may give us a standard to judge of the vast exodus in progress from Arabia, and the rapid strides by which the crowded harems multiplied the race. Arab ladies, as a rule, married only Arab husbands; but the other sex, besides unlimited indulgence in servile concubinage, were free to contract marriage with the women of conquered lands, whether converts or ‘people of the Book;’ for marriage is lawful between a Moslem and females of the Jewish and Christian faith. And although the wives of Arab blood took precedence in virtue of rank and birth, the children also of every Arab father, whether the mother were slave or free, Moslem, Jew, or Christian, were equal in legitimacy. And so the nation multiplied. Looking to these considerations and to the new drain upon Arabia to meet the conquests in Egypt and Persia (of which anon), we shall not greatly err if we assume that before Omar’s death the number of Arabs beyond the limits of Arabia proper, reached to Half a million, and eventually doubled, perhaps quadrupled. [Sidenote: Provincial administration.] Civil administration followed in the wake of conquest. In Chaldæa, the great network of canals was early taken in hand. The long-neglected embankments of the Euphrates were placed under charge of a special officer, and those of the Tigris under another. Syria and Irâc were measured field by field; and the assessment of the lands, both crown and provincial, established on a uniform system. In Irâc, the agency of the Dihcâns, or great landholders, was taken advantage of, as under the Sassanide dynasty, to aid in the police and revenue administration. [Sidenote: Reserves of cavalry.]