Page:Micrographia - or some physiological descriptions of minute bodies made by magnifying glasses with observations and inquiries thereupon.djvu/71

Rh how much of the pressure of the Air is taken off by its ingress into smaller and smaller holes. From the application of which to the entring of the Air into the bigger hole of the Vessel, and into the smaller hole of the Pipe, we shall clearly find, that there is a greater pressure of the air upon the water in the Vessel or greater pipe, then there is upon that in the lesser pipe: For since the pressure of the air every way is found to be equal, that is, as much as is able to press up and sustain a Cylinder of Quicksilver of two foot and a half high, or thereabouts; And since of this pressure so many more degrees are required to force the Air into a smaller then into a greater hole that is full of a more congruous fluid. And lastly, since those degrees that are requisite to press it in, are thereby taken off from the Air within, and the Air within left with so many degrees of pressure less then the Air without; it will follow, that the Air in the less Tube or pipe, will have less pressure against the superficies of the water therein, then the Air in the bigger: which was the minor Proposition to be proved.

The Conclusion therefore will necessarily follow, viz. That this unequal pressure of the Air caused by its ingress into unequal holes, is a cause sufficient to produce this effect, without the help of any other concurrent; therefore is probably the principal (if not the only) cause of these Phænomena.

This therefore being thus explained, there will be divers Phænomena explicable thereby, as, the rising of Liquors in a Filtre, the rising of Spirit of Wine, Oyl, melted Tallow, &c. in the Week of a Lamp, (though made of small Wire, Threeds of Asbestus, Strings of Glass, or the like) the rising of Liquors in a Spunge, piece of Bread, Sand, &c. perhaps also the ascending of the Sap in Trees and Plants, through their small, and some of them imperceptible pores, (of which I have said more, on another occasion) at least the passing of it out of the earth into their roots. And indeed upon the consideration of this Principle, multitudes of other uses of it occurr'd to me, which I have not yet so well examined and digested as to propound for Axioms, but only as Queries and Conjectures which may serve as hints toward some further discoveries.

As first, Upon the consideration of the congruity and incongruity of Bodies, as to touch, I found also the like congruity and incongruity (if I may so speak) as to the Transmitting of the Raies of Light: For as in this regard, water (not now to mention other Liquors) seems nearer of affinity to Glass then Air, and Air then Quicksilver: whence an oblique Ray out of Glass, will pass into water with very little refraction from the perpendicular, but none out of Glass into Air, excepting a direct, will pass without a very great refraction from the perpendicular, nay any oblique Ray under thirty degrees, will not be admitted into the Air at all. And Quicksilver will neither admit oblique or direct, but reflects all; seeming, as to the transmitting of the Raies of Light, to be of a quite differing constitution, from that of Air, Water, Glass, &c. and to resemble most those opacous and strong reflecting bodies of Metals: So also as to the property of cohesion or congruity, Water seems to keep the same order, being Rh