Page:Micrographia - or some physiological descriptions of minute bodies made by magnifying glasses with observations and inquiries thereupon.djvu/67

Rh or included within any of the other Liquors (by which recited Liquors, may be plainly enough represented the four Peripatetical Elements, and the more subtil Æther above all.) From this property 'tis, that a drop of water does not mingle with, or vanish into Air, but is driven (by that Fluid equally protruding it on every side) and forc't into as little a space as it can possibly be contained in, namely, into a Round Globule. So likewise a little Air blown under the water, is united or thrust into a Bubble by the ambient water. And a parcel of Quick-silver enclosed with Air, Water, or almost any other Liquor, is formed into a round Ball.

Now the cause why all these included Fluids, newly mentioned, or as many others as are wholly included within a heterogeneous fluid, are not exactly of a Spherical Figure (seeing that if caused by these Principles only, it could be of no other) must proceed from some other kind of pressure against the two opposite flatted sides. This adventitious or accidental pressure may proceed from divers causes, and accordingly must diversifie the Figure of the included heterogeneous fluid: For seeing that a body may be included either with a fluid only, or only with a solid, or partly with a fluid, and partly with a solid, or partly with one fluid, and partly with another; there will be found a very great variety of the terminating surfaces, much differing from a Spherical, according to the various resistance or pressure that belongs to each of these encompassing bodies.

Which Properties may in general be deduced from two heads, ''viz. Motion, and Rest''. For, either this Globular Figure is altered by a natural Motion, such as is Gravity, or a violent, such as is any accidental motion of the fluids, as we see in the wind ruffling up the water, and the purlings of Streams, and foaming of Catarracts, and the like. Or thirdly, By the Rest, Firmness and Stability of the ambient Solid. For if the including Solid be of an angular or any other irregular Form, the included fluid will be near of the like, as a Pint-Pot full of water, or a Bladder full of Air. And next, if the including or included fluid have a greater gravity one than another, then will the globular Form be deprest into an Elliptico-spherical: As if, for example, we suppose the Circle A B C D, in the fourth Figure, to represent a drop of water, Quick-silver, or the like, included with the Air or the like, which supposing there were no gravity at all in either of the fluids, or that the contained and containing were of the same weight, would be equally comprest into an exactly spherical body (the ambient fluid forcing equally against every side of it.) But supposing either a greater gravity in the included, by reason whereof the parts of it being prest from A towards B, and thereby the whole put into motion, and that motion being hindred by the resistance of the subjacent parts of the ambient, the globular Figure A D B C will be deprest into the Elliptico-spherical, E G F H. For the side A is detruded to E by the Gravity, and B to F by the resistance of the subjacent medium: and therefore C must necessarily be thrust to G; and D to H. Or else, supposing a greater gravity in the ambient, by whose more then ordinary pressure against the under side of the included globule; B will be forced to F, and by its resistance of Rh