HYDRAULICS

, the science of the motion of water and other fluids, with its application in artificial water-works of all sorts.—As to what respects merely the equilibrium of fluids, or their gravitation or action at rest, belongs to Hydrostatics. Upon removing or destroying that equilibrium, motion ensues; and here Hydraulics commence. Hydraulics therefore suppose Hydrostatics; and many writers, from the near relation between them, like mechanics and statics, join the two together, and treat of them conjointly as one science.

The laws of Hydraulics are given under the word Fluid. And the art of raising water, with the several machines employed for that purpose, are described under their several names, Fountain, Hydrocanisterium Pump, Siphon, Syringe, &c.

The principal writers who have cultivated and improved Hydraulics and Hydrostatics, are Archimedes, in his Libris de Insidentibus Humido; Hero of Alexandria, in his Liber Spiritualium; Marinus Ghetaldus, in his Archimedes promotus; Mr. Oughtred; Jo. Ceva, in his Geometria Motus; Jo. Bap. Balianus, De Motu Naturali Gravium, Solidorum et Liquidorum; Mariotte, in his treatise of the Motion of Water and other fluids; Boyle, in his Hydrostatical Paradoxes; Fran. Tertius de Lanis, in his Magisterium Naturæ et Artis; Lamy, in his Traité de l'Equilibre des Liqueurs; Rohault; Dr. Wallis, in his Mechanics; Dechales; Newton, in his Principia; Gulielmeni, in his Mensura Aquarum Fluentium; Herman; Wolsius; Gravesande; Musschenbroek; Leopold; Schottus, in his Mechanica Hydraulico Pneumatica; Geo. Andr. Bockler, in his Architectura Curiosa Germanica; August. Rammilleis; Lucas Antonius Portius; Sturmy, in his treatise on the Construction of Mills; Switzer's Hydrostatics; Varignon, in the Mem. Acad. Sci.; Jurin; Belidor; Bernoulli; Desaguliers; Clare; Emerson; Ferguson; Ximenes; Bossu; D'Alembert; Buat; &c, &c.

HYDRAULICO-Pneumatical, a term applied by some authors to such engines as raise water by means of the weight or spring of the air.

HYDROGRAPHICAL Charts or Maps, more usually called sea-charts, are projections of some part of the sea, or coast, for the use of navigation-

In these are laid down all the rhumbs or points of the compass, the meridians, parallels, &c, with the coasts, capes, islands, rocks, shoals, shallows, &c, in their proper places, and proportions. |

The making and selling these charts was for some time the employment of Columbus, the first discoverer of America. The story goes, that happening to be heir to the memoirs and journals of one Alonzo Sanchez de Huelva, a noted pilot and captain of a ship, who by chance had been driven by a storm to the island of St. Domingo, and dying at Columbus's house soon after his return, this gave Columbus the first hint to attempt a discovery of the West Indies.

For the construction and use of the several kinds of Hydrographical Maps, see Chart, and Sailing.