Nevertheless, this useful invention, which we could not now dispense with, made so little progress during four centuries that princes thought it a duty to protect, by several laws, those establishments, still rare, but which people began to appreciate. Honorius and Arcadius decreed, in 398, that any person who turned the water from mills for his own profit, should be punished by a fine of five pounds weight in gold; and that any magistrate encouraging such an act should pay a like sum.[III-36] The Emperor Zeno[III-37] maintained this law, and rendered it still more stringent by adding, that the edifices or land into which the water had been turned should be confiscated.[III-38] It is to be regretted that the precise origin of the miller’s profession cannot be traced; but, alas! in almost all the arts which tend to preserve life, we discover the same uncertainty: we are ignorant of the period of their discovery, and it frequently happens that but few traces of their development remain. On the contrary, the dates of battles, or scourges which have decimated the human race, are certain enough: the stain of blood leaves an impression which can never be effaced. In the midst of the conflicting opinions of the writers of antiquity, what appears most probable is, that watermills were invented in Asia Minor, and that they were not really used in Rome till the reign of Honorius and Arcadius. Under the rule of the Emperor Justinian, when the Goths besieged the Roman city,[III-39] the celebrated Belisarius thought of constructing some on the Tiber. The means which he employed were simple and ingenious. Two boats firmly fixed, at two feet distance from each other, caused the stream to give a rapid motion to the hydraulic wheel, suspended by its axle between these lateral points of support; and this wheel turned the mills.[III-40] This system differed but little from that of Vitruvius, which he described more than five centuries before, and is explained in a few words. A little wheel, fixed to the axle of the hydraulic wheel, turned a third wheel, adhering to the axle of the upper grindstone, and the corn fell between the two stones in passing from the hopper placed above.[III-41] These grindstones were made of a kind of porous lava, which retained its roughness, or rather, its roughness was renewed, by the continual friction.[III-42] The introduction of watermills, however, did not prevent the use of those worked by hand, which habit, cheapness, and facility of removal recommended: these antique mills of the Hebrews, the Egyptians, and the Greeks of the heroic times, were only five feet high. Each family was supplied with as many as they might require. In the residence of Ulysses, that great king of little Ithaca, there were as many as twelve. Women turned the mills, and were obliged to deliver a certain quantity of flour before leaving the task imposed on them.[III-43]