Fig. 73 represents one of the earliest forms of _a double gutter_, placed across a trough or reservoir designed to receive the water. A partition is formed in the center, and two openings made through the bottom on each of its sides, through which the water that is raised escapes. The machine is worked by one or more men, who alternately plunge the ends into the water, and thus produce a continuous discharge. [Illustration: FIG. 73.] Sometimes, openings are made in the bottom next the laborers, and covered by flaps, to admit the water without the necessity of wholly immersing those ends; machines of this kind probably date from remote antiquity; they are obviously modifications of the _Jantu_ of Hindostan and other parts of Asia. The jantu is a machine extensively used in parts of India, to raise water for the irrigation of land, and is thus described: “It consists of a hollow trough of wood, about fifteen feet long, six inches wide, and ten inches deep, and is placed on a horizontal beam lying on bamboos fixed in the bank of a pond or river. One end of the trough as shown in the figure rests upon the bank where a gutter is prepared to carry off the water, and the other end is dipped in the water, by a man standing on a stage, plunging it in with his foot. A long bamboo with a large weight of earth at the farther end of it, is fastened to the end of the jantu near the river, and passing over the gallows, poises up the jantu full of water, and causes it to empty itself into the gutter. This machine raises water three feet, but by placing a series of them one above another, it may be raised to any height, the water being discharged into small reservoirs, sufficiently deep to admit the jantu above, to be plunged low enough to fill it;” water is thus conveyed over rising ground to the distance of a mile and more. In some parts of Bengal, they have different methods of raising water, but the principle is the same. _The Tympanum._ This is a water raising current wheel originally made in the form of a drum, hence the name. It is now a circular open frame wheel, fitted with radial partitions as shown in Fig. 74, so curved as to point upward on the rising side of the wheel and downward on the descending side. The wheel is so suspended that its lower edge is just submerged and is turned by the current (or by other power), the partitions scooping up a quantity of water which, as the wheel revolves, runs back to the axis of the wheel where it is discharged; or it may discharge at some point of the periphery; while one of the most ancient forms of water lifting machines it is still used in drawing works. [Illustration: FIG. 74.] A little study of the figure (74) will explain its operation.