ASCENT OF FLUIDS

ASCENT OF FLUIDS,is particularly understood of their rising above their own Level between the Surfaces of nearly contiguous Bodies, or in slender capillary Glass Tubes, or in Vessels filled with Sand, Ashes, or the like porous Substance, See FLUID. This Effect happens as well in vacuo as in the open Air, and in crooked as well as straight Tubes. — Some Liquids, as Spirit of Wine, and Oil of Turpentine, ascend swifter than others; and some rise after a different manner from others. Mercury does not ascend at all, but rather subsides. The Phenomenon, with its Causes, etc. in the instance of Capillary Tubes, will be spoke of more at large under the Article Capillary Tube. As to Planes—Two smooth polished Plates of Glass, Metal, Stone, or other Matter, being so disposed as to be almost contiguous, have the Effect of several parallel capil- lary Tubes; and the Fluid rises in them accordingly, the like may be said of a Vessel filled with Sand, etc. the divers little Interstices whereof form, as it were, a kind of Capil- lary Tubes. So that the same Principle accounts for the Appearance in them all. And to the same may probably be ascribed the Ascent of the Sap in Vegetables.
See VEGETABLE and VEGETATION.
Thus Sir I. Newton— If a large Pipe of Glass be filled with sifted Ashes well pressed together, and one End dipped into stagnant Water, the Fluid will ascend slowly in the Ashes, so as in the Space of a Week or Fortnight, to reach the Height of 30 or 40 Inches above the stagnant Water. This Ascent is wholly owing to the Action of those Particles of the Ashes which are upon the Surface of the elevated Water; those within the Water attracting as much downwards as upwards: It follows, that the Action of such Particles is very strong; though being less dense and close than those of Glass, their Action is not equal to that of Glass, which keeps Quicksilver suspended to the Height of 60 or 70 Inches, and therefore acts with a Force which would keep Water suspended to the Height of above 60 Feet.—By the same Principle, a Sponge sucks in Water, and the Glands in the Bodies of Animals, according to their several Natures and Dispositions, imbibe various Juices from the Blood. Opticks, p. 367.
If a Drop of Oil, Water, or other Fluid, be laid on a Glass Plane perpendicular to the Horizon, so as to stand without breaking or running off; and another Plane inclined to the former, so as to meet a-top, be brought to touch the Drop; then will the Drop break, and ascend towards the touching End of the Planes: And it will ascend the fa- ster in proportion as it is higher, by reason the Distance be- tween the Planes is constantly diminishing —After the same manner, the Drop may be brought to any part of the Planes, either upward or downward, or sideways, by altering the Angle of Inclination.
Lastly, if the same perpendicular Planes be so placed, as that two of their Sides meet and form a small Angle, the other two being only kept apart by the Interposition of some thin Body; and thus immersed in a Fluid tinged with some Colour: The Fluid will ascend between the Planes and this the highest where the Planes are nearest; so as to form a Curve Line, which is found to be a just Hyperbola, one of the Asymptotes whereof, is the Line of the Fluid, the other being a Line drawn along the touching Sides.



The physical Causein all these Phenomena, is the same Power of Attraction. See ATTRACTION.

ASCENT OF FLUIDS