If the taxation of the subject had stopped here, he would have had no just ground of complaint against his rulers. The population of the Empire cannot be estimated at less than forty millions of souls. The highest estimate of the value of the entire tribute, both in money and kind, will scarcely place it at more than ten millions sterling. Thus far, then, the burthen of taxation would certainly not have exceeded five shillings a head per annum. Perhaps it would not have reached half that amount. But, unhappily, neither was the tribute the sole tax which the crown exacted from its subjects, nor had the crown the sole right of exacting taxation. Persian subjects in many parts of the Empire paid, besides their tribute, a water-rate, which is expressly said to have been very productive. The rivers of the Empire were the king’s; and when water was required for irrigation, a state officer superintended the opening of the sluices, and regulated the amount of the precious fluid which might be drawn off by each tribe or township. For the opening of the sluices a large sum was paid to the officer, which found its way into the coffers of the state. Further, it appears that such things as fisheries--and if so, probably salt-works, mines, quarries, and forests--were regarded as crown property, and yielded large sums to the revenue. They appear to have been farmed to responsible persons, who undertook to pay at a certain fixed rate, and made what profit they could by the transaction. The price of commodities thus farmed would be greatly enhanced to the consumer. By these means the actual burthen of taxation upon the subject was rendered to some extent uncertain and indefinite, and the benefits of the fixed tribute system were diminished. But the chief drawback upon it has still to be mentioned. While the claims of the crown upon its subjects were definite and could not be exceeded, the satrap was at liberty to make any exactions that he pleased beyond them. There is every reason to believe that he received no stipend, and that, consequently, the burthen of supporting him, his body-guard, and his Court was intended to fall on the province which had the benefit of his superintendence. Like a Roman proconsul, he was to pay himself out of the pockets of his subjects; and, like that class of persons, he took care to pay himself highly. It has been calculated that one satrap of Babylon drew from his province annually in actual coin a sum equal to L100,000. of our money. We can scarcely doubt that the claims made by the provincial governors were, on the average, at least equal to those of the crown; and they had the disadvantage of being irregular, uncertain, and purely arbitrary.