The First Steam-Boat

( 1$ ) Fluids agree in this with folic! Bodies, viz. That they coninW heavy Particles, and have their gravity Proportionable to "ths Quantity of Matter, in any Tout ion of their Parti. Trom this Gravity it fol- lows, That -the Surface of a Fluid con- tained in a Veifel, if it be not p retted from above, or if equally prefs’d (for that makes no Alteration) will become Plain crrTlat, and parallel to the Horizon: for as the Particles yield to any force im- p refs’cl, they will be moved by Gravi- tytill at bft non? of them can cleicend any Lower. The Lower Partsluftain the Upper, and are prelied by them -, ancithig Preffure is in Troportion to the incumbent Matter'? that is, -to the Height of the Liquid above thePatticle that is preffed. But as the upper Surface of the Li^uidis parallel to the Horizon, all the Toints of any Surface which you may conceive with- in the Liquid parallel to the Horizon are equally prefs’d. If therefore in any Part of fitch a Sur- face there is a leffer Treflure than in other Tarts, the Liquid which yields to any Impreflion will aicejndtill th epiefiure be~ comes equal. Take a Glafs-Tube open at both Ends, and ftopping one End -with É 2, your