Reservoir, a place artificially constructed for the collection and retention of water, in order that it may be conveyed to distant places, by means of pipes.

Reservoirs are at present chiefly employed for the supply of fountains, jets d'eau, and similar volumes of water. Although such contrivances heighten the picturesque scenery of plantations, yet we conceive that they might be rendered productive of greater advantage to agriculturists, by forming them in certain situations, for the reception of flood-waters, and the prevention of many accidents, that happen in consequence of land-floods. Where the soil is naturally porous, and the strata, lying beneath, are so open as to absorb the rain-water during its descent, no floods will easily occur; because the fissures or pores operate as regulators for conducting the streams ; and the discharge becomes so equal, that the humidity remains nearly in the same state throughout the year. In clay, and similar retentive lands, however, a very small portion of water is absorbed, and such large quantities speedily glide off the sur-I face, so that eithier extreme scarcity or superfluity is the necessary result. With a view to remedy these inconveniencies in such soils, it has been proposed to form reservoirs of any depth, and breadth, that may be best adapted to the purpose ; and, as during the heat of summer, the water would be absorbed to the depth of eight or nine inches, this diminution of its volume may be obviated, by raising the top so many inches higher than might otherwise be found -expedient. Farther, such reservoirs may communicate, by means of subterraneous pipes or channels, with some rivulet or brook, that in summer is nearly dry ; but which in the winter is swoln into torrents. In consequence of these hydraulic measures, a regular supply of water will be obtained at all seasons, tor the irrigation of fields or meadows ; and also for turning mills, or other machinery, where a certain velocity is required ; so that the extensive damage frequently occasioned by sudden floods, will thus be effectu-ally prevented.