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takes away and uses up its moisture。 So much for drying。
6
Liquefaction is； first； condensation into water； second； the melting
of a solidified body。 The first； condensation； is due to the cooling
of vapour： what melting is will appear from the account of
solidification。
Whatever solidifies is either water or a mixture of earth and water；
and the agent is either dry heat or cold。 Hence those of the bodies
solidified by heat or cold which are soluble at all are dissolved by
their opposites。 Bodies solidified by the dry…hot are dissolved by
water； which is the moist…cold； while bodies solidified by cold are
dissolved by fire； which is hot。 Some things seem to be solidified
by water； e。g。 boiled honey； but really it is not the water but the
cold in the water which effects the solidification。 Aqueous bodies are
not solidified by fire： for it is fire that dissolves them； and the
same cause in the same relation cannot have opposite effects upon
the same thing。 Again； water solidifies owing to the departure of
heat； so it will clearly be dissolved by the entry into it of heat：
cold； therefore； must be the agent in solidifying it。
Hence aqueous bodies do not thicken when they solidify； for
thickening occurs when the moisture goes off and the dry matter
comes together； but water is the only liquid that does not thicken。
Those bodies that are made up of both earth and water are solidified
both by fire and by cold and in either case are thickened。 The
operation of the two is in a way the same and in a way different。 Heat
acts by drawing off the moisture； and as the moisture goes off in
vapour the dry matter thickens and collects。 Cold acts by driving
out the heat； which is accompanied by the moisture as this goes off in
vapour with it。 Bodies that are soft but not liquid do not thicken but
solidify when the moisture leaves them； e。g。 potter's clay in
process of baking： but those mixed bodies that are liquid thicken
besides solidifying； like milk。 Those bodies which have first been
thickened or hardened by cold often begin by becoming moist： thus
potter's clay at first in the process of baking steams and grows
softer； and is liable to distortion in the ovens for that reason。
Now of the bodies solidified by cold which are made up both of earth
and water but in which the earth preponderates； those which solidify
by the departure of heat melt by heat when it enters into them
again； this is the case with frozen mud。 But those which solidify by
refrigeration； where all the moisture has gone off in vapour with
the heat； like iron and horn； cannot be dissolved except by
excessive heat； but they can be softened…though manufactured iron does
melt； to the point of becoming fluid and then solidifying again。
This is how steel is made。 The dross sinks to the bottom and is
purged away： when this has been done often and the metal is pure we
have steel。 The process is not repeated often because the purification
of the metal involves great waste and loss of weight。 But the iron
that has less dross is the better iron。 The stone pyrimachus； too；
melts and forms into drops and becomes fluid； after having been in a
fluid state it solidifies and becomes hard again。 Millstones； too；
melt and become fluid： when the fluid mass begins to solidify it is
black but its consistency comes to be like that of lime。 and earth；
too
Of the bodies which are solidified by dry heat some are insoluble；
others are dissolved by liquid。 Pottery and some kinds of stone that
are formed out of earth burnt up by fire； such as millstones； cannot
be dissolved。 Natron and salt are soluble by liquid； but not all
liquid but only such as is cold。 Hence water and any of its
varieties melt them； but oil does not。 For the opposite of the dry…hot
is the cold…moist and what the one solidified the other will dissolve；
and so opposites will have opposite effects。
7
If a body contains more water than earth fire only thickens it： if
it contains more earth fire solidifies it。 Hence natron and salt and
stone and potter's clay must contain more earth。
The nature of oil presents the greatest problem。 If water
preponderated in it； cold ought to solidify it； if earth
preponderated； then fire ought to do so。 Actually neither
solidifies； but both thicken it。 The reason is that it is full of
air （hence it floats on the top of water； since air tends to rise）。
Cold thickens it by turning the air in it into water； for any
mixture of oil and water is thicker than either。 Fire and the lapse of
time thicken and whiten it。 The whitening follows on the evaporation
of any water that may have been in it； the is due to the change of the
air into water as the heat in the oil is dissipated。 The effect in
both cases is the same and the cause is the same； but the manner of
its operation is different。 Both heat and cold thicken it； but neither
dries it （neither the sun nor cold dries oil）； not only because it
is glutinous but because it contains air。 Its glutinous nature
prevents it from giving off vapour and so fire does not dry it or boil
it off。
Those bodies which are made up of earth and water may be
classified according to the preponderance of either。 There is a kind
of wine； for instance； which both solidifies and thickens by boiling…I
mean； must。 All bodies of this kind lose their water as they That it
is their water may be seen from the fact that the vapour from them
condenses into water when collected。 So wherever some sediment is left
this is of the nature of earth。 Some of these bodies； as we have said；
are also thickened and dried by cold。 For cold not only solidifies but
also dries water； and thickens things by turning air into water。
（Solidifying； as we have said； is a form of drying。） Now those
things that are not thickened by cold； but solidified； belong rather
to water； e。g。。 wine； urine； vinegar； lye； whey。 But those things that
are thickened （not by evaporation due to fire） are made up either of
earth or of water and air： honey of earth； while oil contains air。
Milk and blood； too； are made up of both water and earth； though earth
generally predominates in them。 So； too； are the liquids out of
which natron and salt are formed； and stones are also formed from some
mixtures of this kind。 Hence； if the whey has not been separated； it
burns away if you boil it over a fire。 But the earthy element in
milk can also be coagulated by the help of fig…juice； if you boil it
in a certain way as doctors do when they treat it with fig…juice；
and this is how the whey and the cheese are commonly separated。
Whey； once separated； does not thicken； as the milk did； but boils
away like water。 Sometimes； however；