, as a
piece of Cork under it, but it presently _emerges_ or _swims_ as 'twere on
the top; nor can you lay a _heavier_ on the top of it, as a piece of Lead,
but it is immediately _buried_ in Sand, and (as 'twere) sinks to the
bottom. Nor can you make a _hole_ in the side of the Dish, but the sand
shall _run out_ of it to a _level_, not an _obvious property_ of a fluid
body, as such, but this dos _imitate_; and all this meerly caused by the
vehement _agitation_ of the conteining vessel; for by this means, _each_
sand becomes to have a _vibrative_ or _dancing_ motion, so as no other
heavier body can _rest_ on it, unless _sustein'd_ by some other on either
side: Nor will it suffer any Body to be _beneath_ it, unless it be a
_heavier_ then it self. Another Instance of the strange _loosening_ nature
of a violent jarring Motion, or a strong and nimble vibrative one, we may
have from a piece of _iron_ grated on very strongly with a _file_: for if
into that a pin _screw'd_ so firm and hard, that though it has a convenient
head to it, yet it can by no means be _unscrew'd_ by the fingers; if, I
say, you attempt to unscrew this whilst _grated on by the file_, it will be
found to undoe and turn very _easily_. The first of these Examples
manifests, how a body actually _divided_ into small parts, becomes a
_fluid_. And the latter manifests by what means the agitation of heat so
easily _loosens_ and _unties_ the parts of _solid_ and _firm_ bodies. Nor
need we suppose heat to be any thing else, besides such a motion; for
supposing we could _Mechanically_ produce such a one _quick_ and _strong_
enough, we need not spend _fuel_ to _melt_ a body. Now, that I do not speak
this altogether groundless, I must refer the Reader to the Observations I
have made upon the shining sparks of Steel, for there he shall find that
_the same_ effects are produced upon small chips or parcels of Steel by the
_flame_, and by _a quick and violent motion_; and if the body of _steel_
may be thus melted (as I there shew it may) I think we have little reason
to doubt that almost _any other_ may not also. Every Smith can inform one
how quickly both his _File_ and the _Iron_ grows _hot_ with _filing_, and
if you _rub_ almost any two _hard_ bodies together, they will do the same:
And we know, that a sufficient degree of heat causes _fluidity_, in some
bodies much sooner, and in others later; that is, the parts of the body of
some are so _loose_ from one another, and so