incongruous then _Air_ (and thereby being put into a _Glass-pipe_, will not adhere to it, but by the more _congruous air_ will be forced to have a very _protuberant_ surface, and to rise higher in a greater then a lesser Pipe) this _Quicksilver_ to clean _Metal_, especially to _Gold_, _Silver_, _Tin_, _Lead_, &c. _Iron_ excepted, is more _congruous_ then _Air_, and will not only stick to it, but have a _concave_ Surface like _water_, and rise higher in a less, then in a greater Pipe. In all these Examples it is evident, that there is an _extraordinary_ and _adventitious force_, by which the _globular_ Figure of the contained _heterogeneous_ fluid is altered; neither can it be imagined, how it should otherwise be of any other Figure then _Globular_: For being by the _heterogeneous_ fluid equally _protruded_ every way, whatsoever part is _protuberant_, will be thereby _deprest_. From this cause it is, that in its effects it does very much resemble a _round Spring_ (such as a _Hoop_.) For as in a _round Spring_ there is required an additional _pressure_ against two opposite sides, to reduce it into an _Oval_ Form, or to force it in between the sides of a _Hole_, whose _Diameter_ is less then that of the _Spring_, there must be a considerable force or _protrusion_ against _the concave_ or inner side of the _Spring_; So to alter this _spherical_ constitution of an included fluid body, there is required more pressure against opposite sides to reduce it into an _Oval_; and, to press it into an _Hole_ less in _Diameter_ then it self, it requires a greater _protrusion_ against all the other sides, What degrees of force are requisite to reduce them into longer and longer _Ovals_, or to press them into less and less _holes_, I have not yet experimentally calculated; but thus much by experiment I find in general, that there is alwayes required a greater pressure to close them into longer _Ovals_, or protrude them into smaller _holes_. The necessity and reason of this, were it requisite, I could easily explain: but being not so necessary, and requiring more room and time then I have for it at present, I shall here omit it; and proceed to shew, that this may be presently found true, if Experiment be made with a _round Spring_ (the way of making which trials is _obvious_ enough.) And with the fluid bodies of _Mercury_, _Air_, _&c._ the way of trying which, will be somewhat more difficult; and therefore I shall in brief describe it. He therefore that would try with _Air_, must first be provided of a _Glass-pipe_, made of the shape of that in the _fifth Figure_, whereof the side AB, represents a straight _Tube_ of about three foot long, C, represents another part of it, which consists of a _round Bubble_; so ordered, that there is left a _passage_ or _hole_ at the top, into which may be fastened with _cement_ several _small Pipes_ of determinate _cylindrical_ cavities: as let the _hollow_ of