It was more than an ancient observation that came down to Pliny’s time for record, that water would rise to a level with its source. The observation, however, was put into practical use in his time and long before without a knowledge of its philosophical cause. Nothing in Egyptian sculpture portraying the arts in vogue around the cradle of the human race is older than the long lever rocking upon a cleft stick, one arm of the lever carrying a bracket and the other arm used to raise a bucket from a well. Forty centuries and more have not rendered this device obsolete. Among other machines of the Egyptians, the Carthaginians, the Greeks, and the Romans for raising water was the _tympanum_, a drum-shape wheel divided into radial partitions, chambers, or pockets, which were open to a short depth on the periphery of the wheel, and inclined toward the axis, and which was driven by animal or manual power. These pockets scooped up the water from the stream or pond in which the wheel was located as the wheel revolved, and directed it toward the axis of the wheel, where it ran out into troughs, pipes, or gutters. The _Noria_, a chain of pots, and the screw of Archimedes were other forms of ancient pumps. The bucket pumps with some modifications are known in modern times as scoop wheels, and have been used extensively in the drainage of lands, especially by the Dutch, who at first drove them by windmills and later by steam. The division of water-wheels into overshot, undershot and breast wheels is not a modern system. In the _Pneumatics of Hero_, which compilation of inventions appeared in 225 B. C., seventy-nine illustrations are given and described of simple machines, between sixty and seventy of which are hydraulic devices. Among these, are siphon pumps, the force pump of Ctesibius, a “fire-pump,” having two cylinders, and two pistons, valves, and levers. We have in a previous chapter referred to Hero’s steam engine. The fact that a vacuum may be created in a pump into which water will rise by atmospheric pressure appears to have been availed of but not explained or understood. The employment of the rope, pulley and windlass to raise water was known to Hero and his countrymen as well as by the Chinese before them. The chain pump and other pumps of simple form have only been improved since Hero’s day in matters of detail. The screw of Archimedes has been extended in application as a carrier of water, and converted into a conveyor of many other materials. Thus, aqueducts, reservoirs, water-wheels (used for grinding grain), simple forms of pumps, fountains, hydraulic organs, and a few other hydraulic devices, were known to ancient peoples, but their limited knowledge of the laws of pneumatics and their little mechanical skill prevented much general progress or extensive general use of such inventions.