Hydro dolomite

( Min. ) A yellowish-white min Comp. Lime 25-22, carbonic acid 33-10, magnesia 24-28, water 17-40. Hydrodynamic, Hydrodynamical, a . [Gr. hudor, water, and dynamikos , powerful, from dynamis , power, force, from dynamai , to be able, strong enough -probably from Sansk. tan , to do, accomplish, create.] Pertaining to the force or pre ure of water. Hydrodynamics, n . pl . [Gr. hudor , water, du nam is, power.] That branch of science which treats of the pre ure, equilibrium, cohesion, and motion of fluids, and also of the machines by which water is raised, or in which water is used as the first mover. The subject is divided into two parts, -hydrostatics and hydraulics. The former includes the pre ure, cohesion, and equilibrium of fluids, while the latter comprehends their motion, together with the machines with which they are connected. Many of the laws of hydrodynamics depend greatly upon the characteristic property of fluids; namely, that of transmitting equally in all directions pre ures applied at their surfaces. As a science, hydrodynamics is, comparatively speaking, modern. It was cultivated with le succe by the ancients than any other branch of mechanical philosophy. The general principles, however, upon which the science of hydrostatics is founded were first given by Arch i me des, about 250 years before the birth of Christ. He maintained that each particle of a fluid in equilibrio is equally pre ed in every direction. He also inquired into the conditions according to which a solid body floating in a fluid should a ume and preserve a position of equilibrium. The first attempts at the construction of hydraulic machinery were made in a Greek school at Alexandria, which flourished under the patronage of the Ptolemies. The fountain of compre ion, the siphon, and the forcing-pump were invented by Cteribus and Hero, about 120 years after the birth of Christ. The siphon, a simple instrument used for emptying ve els, and the forcing-pump, a more complicated machine, will be found described in the articles PUMP, SIPHON. The fountain of Hero (Fig. 1052), as it is usually called, is a machine, the principle of which depends upon the transmi ion of the pre ure sustained by a body of water in one ve el to that in another. by means of the elasticity of air. An apparatus constructed on the principle of the fountain of Hero is employed for draining the water from the mines of Schemnitz, in Hungary. Notwithstanding these inventions of the Alexandrian school, its attention does not seem to have been directed to the motion of fluids. The first attempt to investigate this subject was made at Rome, in the reigns of Nerva and Trajan. From that time very little advance was made in hydrodynamics till the end of the 16th century, when the discoveries of Castelli and Torr i cell i gave a new direction to the science of hydraulics. The discoveries of Sir Isaac Newton and other philosophers have caused this branch of science to progre rapidly in later years. The analytical theory of hydrodynamics resolves itself into the integration of equations of partial differences. Euler, to whom this branch of the calculus is owing, gave the general formulæ for the motion of fluids, founded on the laws of their equilibrium, and thus reduced the whole mechanics of fluid bodies to a single question of analysis. Hydraulic machines are of great variety. They are of two kinds, - machines having a motion of rotation, and machines having an alternate motion. When water acts on a machine as a moving power, it exerts, on the part impinged on, a pre ure. The immediate effect of this pre ure will be to make the part struck move in the direction of the power, or in some constrained direction; in either case the space will be pa ed through by the part. Among the machines having a motion of rotation may be mentioned water-wheels of varied kinds. They may be divided into two cla es, -vertical wheels, with the axis horizontal, and horizontal wheels, with the axis vertical. The hydraulic machines which po e an alternate motion are the water-column machine and the hydraulic ram (which see). The water-column machine consists of a cylinder in which a piston is driven backwards and forwards by the weight of a high column of water contained in an upright pipe. A working-beam is attached to the piston-rod, which transmits a motion to the common pumps. This machine, used in Hungary, is mentioned above as an adaptation of the principle of Hero's fountain. The machines for raising water are pumps , - the Arch i me des' screw, and pail or bucket, machines . Descriptions of the different hydraulic machines are given under the respective names of each.