decomposition continues until the smaller either escapes to its kindred
element or becomes one with its conqueror. And this tendency in bodies to
condense or escape is a source of motion...Where there is motion there must
be a mover, and where there is a mover there must be something to move.
These cannot exist in what is uniform, and therefore motion is due to want
of uniformity. But then why, when things are divided after their kinds, do
they not cease from motion? The answer is, that the circular motion of all
things compresses them, and as 'nature abhors a vacuum,' the finer and more
subtle particles of the lighter elements, such as fire and air, are thrust
into the interstices of the larger, each of them penetrating according to
their rarity, and thus all the elements are on their way up and down
everywhere and always into their own places. Hence there is a principle of
inequality, and therefore of motion, in all time.

In the next place, we may observe that there are different kinds of fire--
(1) flame, (2) light that burns not, (3) the red heat of the embers of
fire. And there are varieties of air, as for example, the pure aether, the
opaque mist, and other nameless forms. Water, again, is of two kinds,
liquid and fusile. The liquid is composed of small and unequal particles,
the fusile of large and uniform particles and is more solid, but
nevertheless melts at the approach of fire, and then spreads upon the
earth. When the substance cools, the fire passes into the air, which is
displaced, and forces together and condenses the liquid mass. This process
is called cooling and congealment. Of the fusile kinds the fairest and
heaviest is gold; this is hardened by filtration through rock, and is of a
bright yellow colour. A shoot of gold which is darker and denser than the
rest is called adamant. Another kind is called copper, which is harder and
yet lighter because the interstices are larger than in gold. There is
mingled with it a fine and small portion of earth which comes out in the
form of rust. These are a few of the conjectures which philosophy forms,