2l6

Mechanics.

the Axis on a fine Point moves in the Pivot Hole in thePart of the Frame at T ; on the upper Part of theFrame is a Hole thro' which the Spindle passes, as alsothro' the round circular Piece P fix’d on the said Frame ;on the upper Part of the Spindle is fix’d another roundcircular Piece O, which represents the upper move-able Stone of the Mill. Qjs a Spout of Water fillingthe Tube or Trunk, and giving Motion thereto, andconsequently to the Axis and upper Stone, by the hori-zontal Jets of Water from each End cf the Trunk IK,thro’ Holes made at each End on contrary Sides.

32. While the Holes continue stopped, the Trunkwill be at rest, because then the Pressure is equal overall the Parts: hut when the Holes are open, the Pres-sure of the Water (by its having Liberty to issue out)will be less on that Part where the Hole is, than onthe other Part opposite to it; which stronger Pressurewill prevail, and carry round the Trunk and Tubewith the Axle and Stone, in a contrary Direction ; andeach Hole contributes to produce this Motion, whichwill be greater or lesser in Proportion to the Momentaof the Jets of Water, or greater or lesser Aperture ofthe Holes.

33. For it is easy to understand, that the Power ofthis Machine is derived from, or depends upon, threeThings: (1.) The Velocity of the Spouting Water ;(2.) The Quantity thereof; and (3.) The Distance atwhich the Water spouts from the Axis of Motion. Thetwo first make the Momentum arising from the Pressureof the Fluid, which is proportional to the Altitude, orHeight of the Tube ; the last is of a Mechanical Na-ture, for the Trunk is in this respect exactly of the Na-ture of the Lever.

34. In the Lecture of Hydrostatics it will be shewn,that the Velocity of the Spouting Fluid will be as theSquare Root of the Altitude of the Fluid ; whence thisPart of the Force will be in the Subduplicate Ra to of theHeight of the Tube. The Quantity of the spoutingFluid will be also in the same Ratio, while the Aper-tures are the fame ; but if these vary their Magnitude,it will be directly as the Aperture, the Altitudes beinggiven. Therefore the whole Momentum arising from

these