Wind p/oducedthe fall ojWati-r ; hyDr. Wal. Pope,n. 2. p. 25.

P-L» l 79*

yhe bfß surrn Oj'Horizontal Saihfor a Mill ; 6v/v.RobHook,ibtl. Coll.

;i. 3. {. ( 51 .

t-'iz. 180.

C;86)

t'.ieir Sc/uare Roots as I have siid above, which Rcots arc 19 and 1, we mayConclude that the Velocjty of Air must Exceed that of Water by 29 Times :and Ib Multiplying 45, the Vclocity of Water, by 29, \ve {hall sind, that theVelccity of the Air driven by the wholc Prcfl'ure of the Atmtfpbere, is about1 zos Foot in a Second.

XIII. In the Brafs-Work,s at Tivoü, the [Vater Bloxvs the Firc, not byMoving the Bellows, but by affording the Wmd. Thus : A, is the River.B, the Fall of it. C, the Tube into which it Falls. LG, a Pipc. G, the O ri-sce of the Pipc, or Hofe of the Bcllows. G K, the Heartb. E, a Hole in thePipc. F, a Stopper to that Hole. D, a place under-ground, by which theWatcr runs away. Stopping the Hole E, there is a perpetual strong Wind, ,iiTuing forth at G: and G being stopt, the [find comes out Ib Vchement-ly at E, that it will, I believe, makc a Ball play, like that at Frcfcati.

f XIV. Whatever Men may imagine conceniing Horizontal Sails , I doubtthere will ne ver be found a better, and more Advantageous way, for recti ving the Strength of the Hstnd, or Motion of the Air, than Perpcndicular Vanesmade of a True Form, Io as every part thereof may Draw alike. But be-causi I find divers have of late attempted Horizontal Vanes for Mills, I fliallexplain a way of making Horizontal Vanes capable of Pcrforming the Meßthat is Pofßblc will, Vanes of equal Extensum.

The Invention is Founded upon.the sime Principle wiih that of th e Saiiingta ' Slips, and other. Vcjfels, tipon the Bea ; namely, blpon Dilpoiing and Or-dering ol the Vane or Sail (0, as to stand in the best Posturc bis postble toMove the Arms rf the Milf, or tbe Bödy of the Sbip, in tbar iVcy it is to beMoved, by tbe Force of the Wind Bloxving thus or thus against tlcm.

The First Principle then common to both, is, That . the. Vane or Sali be asnear as ’tis pollible, a perfect Plain and Smootb Superficies, without any Belly-ing, Bunting, or Curvity in the, Superficies thereof, upon which the Motion,or Force of the Wind is ImprelTcd.

Secondly, That the Air may have as Many Pajfagcs between the parts ofthe Vane or Sail as may be, that the Moved Air may come to it as frcely asmay be, without being Intercepted by a Stagnant Air before it, to Impede orDivert its Force.

Tbirdly, That the Plain of the Vane or Sail be put in the Middle Inclinati-ori, between the Way of the Hind and the Way of the Atm, or that of theBody of the Sbip.

The Contrivance it silf is Tbis.

Lct AB, fignific the Strcam or Current of the-Air or Wind, Movingfrom A to B, and let C represint the Center of the Axis or Spindlc, {Und-ing Perpcndicular to the Horizon, upon which, at theTop, .isfixed at RightAngles, the piece D H, making the two Arms C D, and C H, upon theEnds of which the Vanes M N, are Moved on Spindles ; Ib as that the Plainof the Vane doth always pasi through tue Point D : 1 lay, thesi Vanes Iberdered, {hall be always placed in the tuost Advantageous Posture for Moving