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Meteorology By Aristotle

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Author Topic: Meteorology By Aristotle  (Read 1169 times)
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« Reply #90 on: August 31, 2009, 12:07:35 am »

This then is the nature of concoction: but inconcoction is an imperfect
state due to lack of proper heat, that is, to cold. That of which
the imperfect state is, is the corresponding passive qualities which
are the natural matter of anything.

So much for the definition of concoction and inconcoction.

Part 3

Ripening is a sort of concoction; for we call it ripening when there
is a concoction of the nutriment in fruit. And since concoction is
a sort of perfecting, the process of ripening is perfect when the
seeds in fruit are able to reproduce the fruit in which they are found;
for in all other cases as well this is what we mean by 'perfect'.
This is what 'ripening' means when the word is applied to fruit. However,
many other things that have undergone concoction are said to be 'ripe',
the general character of the process being the same, though the word
is applied by an extension of meaning. The reason for this extension
is, as we explained before, that the various modes in which natural
heat and cold perfect the matter they determine have not special names
appropriated to them. In the case of boils and phlegm, and the like,
the process of ripening is the concoction of the moisture in them
by their natural heat, for only that which gets the better of matter
can determine it. So everything that ripens is condensed from a spirituous
into a watery state, and from a watery into an earthy state, and in
general from being rare becomes dense. In this process the nature
of the thing that is ripening incorporates some of the matter in itself,
and some it rejects. So much for the definition of ripening.

Rawness is its opposite and is therefore an imperfect concoction of
the nutriment in the fruit, namely, of the undetermined moisture.
Consequently a raw thing is either spirituous or watery or contains
both spirit and water. Ripening being a kind of perfecting, rawness
will be an imperfect state, and this state is due to a lack of natural
heat and its disproportion to the moisture that is undergoing the
process of ripening. (Nothing moist ripens without the admixture of
some dry matter: water alone of liquids does not thicken.) This disproportion
may be due either to defect of heat or to excess of the matter to
be determined: hence the juice of raw things is thin, cold rather
than hot, and unfit for food or drink. Rawness, like ripening, is
used to denote a variety of states. Thus the liquid and solid excreta
and catarrhs are called raw for the same reason, for in every case
the word is applied to things because their heat has not got the mastery
in them and compacted them. If we go further, brick is called raw
and so is milk and many other things too when they are such as to
admit of being changed and compacted by heat but have remained unaffected.
Hence, while we speak of 'boiled' water, we cannot speak of raw water,
since it does not thicken. We have now defined ripening and rawness
and assigned their causes.
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« Reply #91 on: August 31, 2009, 12:07:53 am »

Boiling is, in general, a concoction by moist heat of the indeterminate
matter contained in the moisture of the thing boiled, and the word
is strictly applicable only to things boiled in the way of cooking.
The indeterminate matter, as we said, will be either spirituous or
watery. The cause of the concoction is the fire contained in the moisture;
for what is cooked in a frying-pan is broiled: it is the heat outside
that affects it and, as for the moisture in which it is contained,
it dries this up and draws it into itself. But a thing that is being
boiled behaves in the opposite way: the moisture contained in it is
drawn out of it by the heat in the liquid outside. Hence boiled meats
are drier than broiled; for, in boiling, things do not draw the moisture
into themselves, since the external heat gets the better of the internal:
if the internal heat had got the better it would have drawn the moisture
to itself. Not every body admits of the process of boiling: if there
is no moisture in it, it does not (for instance, stones), nor does
it if there is moisture in it but the density of the body is too great
for it-to-be mastered, as in the case of wood. But only those bodies
can be boiled that contain moisture which can be acted on by the heat
contained in the liquid outside. It is true that gold and wood and
many other things are said to be 'boiled': but this is a stretch of
the meaning of the word, though the kind of thing intended is the
same, the reason for the usage being that the various cases have no
names appropriated to them. Liquids too, like milk and must, are said
to undergo a process of 'boiling' when the external fire that surrounds
and heats them changes the savour in the liquid into a given form,
the process being thus in a way like what we have called boiling.

The end of the things that undergo boiling, or indeed any form of
concoction, is not always the same: some are meant to be eaten, some
drunk, and some are intended for other uses; for instance dyes, too,
are said to be 'boiled'.

All those things then admit of 'boiling' which can grow denser, smaller,
or heavier; also those which do that with a part of themselves and
with a part do the opposite, dividing in such a way that one portion
thickens while the other grows thinner, like milk when it divides
into whey and curd. Oil by itself is affected in none of these ways,
and therefore cannot be said to admit of 'boiling'. Such then is the
pfcies of concoction known as 'boiling', and the process is the same
in an artificial and in a natural instrument, for the cause will be
the same in every case.
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« Reply #92 on: August 31, 2009, 12:08:08 am »

Imperfect boiling is the form of inconcoction opposed to boiling.
Now the opposite of boiling properly so called is an inconcoction
of the undetermined matter in a body due to lack of heat in the surrounding
liquid. (Lack of heat implies, as we have pointed out, the presence
of cold.) The motion which causes imperfect boiling is different from
that which causes boiling, for the heat which operates the concoction
is driven out. The lack of heat is due either to the amount of cold
in the liquid or to the quantity of moisture in the object undergoing
the process of boiling. Where either of these conditions is realized
the heat in the surrounding liquid is too great to have no effect
at all, but too small to carry out the process of concocting uniformly
and thoroughly. Hence things are harder when they are imperfectly
boiled than when they are boiled, and the moisture in them more distinct
from the solid parts. So much for the definition and causes of boiling
and imperfect boiling.

Broiling is concoction by dry foreign heat. Hence if a man were to
boil a thing but the change and concoction in it were due, not to
the heat of the liquid but to that of the fire, the thing will have
been broiled and not boiled when the process has been carried to completion:
if the process has gone too far we use the word 'scorched' to describe
it. If the process leaves the thing drier at the end the agent has
been dry heat. Hence the outside is drier than the inside, the opposite
being true of things boiled. Where the process is artificial, broiling
is more difficult than boiling, for it is difficult to heat the inside
and the outside uniformly, since the parts nearer to the fire are
the first to get dry and consequently get more intensely dry. In this
way the outer pores contract and the moisture in the thing cannot
be secreted but is shut in by the closing of the pores. Now broiling
and boiling are artificial processes, but the same general kind of
thing, as we said, is found in nature too. The affections produced
are similar though they lack a name; for art imitates nature. For
instance, the concoction of food in the body is like boiling, for
it takes place in a hot and moist medium and the agent is the heat
of the body. So, too, certain forms of indigestion are like imperfect
boiling. And it is not true that animals are generated in the concoction
of food, as some say. Really they are generated in the excretion which
putrefies in the lower belly, and they ascend afterwards. For concoction
goes on in the upper belly but the excretion putrefies in the lower:
the reason for this has been explained elsewhere.
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« Reply #93 on: August 31, 2009, 12:08:23 am »

We have seen that the opposite of boiling is imperfect boiling: now
there is something correspondingly opposed to the species of concoction
called broiling, but it is more difficult to find a name for it. It
would be the kind of thing that would happen if there were imperfect
broiling instead of broiling proper through lack of heat due to deficiency
in the external fire or to the quantity of water in the thing undergoing
the process. For then we should get too much heat for no effect to
be produced, but too little for concoction to take place.

We have now explained concoction and inconcoction, ripening and rawness,
boiling and broiling, and their opposites.

Part 4

We must now describe the forms taken by the passive qualities the
moist and the dry. The elements of bodies, that is, the passive ones,
are the moist and the dry; the bodies themselves are compounded of
them and whichever predominates determines the nature of the body;
thus some bodies partake more of the dry, others of the moist. All
the forms to be described will exist either actually, or potentially
and in their opposite: for instance, there is actual melting and on
the other hand that which admits of being melted.

Since the moist is easily determined and the dry determined with difficulty,
their relation to one another is like that of a dish and its condiments.
The moist is what makes the dry determinable, and each serves as a
sort of glue to the other-as Empedocles said in his poem on Nature,
'glueing meal together by means of water.' Thus the determined body
involves them both. Of the elements earth is especially representative
of the dry, water of the moist, and therefore all determinate bodies
in our world involve earth and water. Every body shows the quality
of that element which predominates in it. It is because earth and
water are the material elements of all bodies that animals live in
them alone and not in air or fire.
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« Reply #94 on: August 31, 2009, 12:08:38 am »

Of the qualities of bodies hardness and softness are those which must
primarily belong to a determined thing, for anything made up of the
dry and the moist is necessarily either hard or soft. Hard is that
the surface of which does not yield into itself; soft that which does
yield but not by interchange of place: water, for instance, is not
soft, for its surface does not yield to pressure or sink in but there
is an interchange of place. Those things are absolutely hard and soft
which satisfy the definition absolutely, and those things relatively
so which do so compared with another thing. Now relatively to one
another hard and soft are indefinable, because it is a matter of degree,
but since all the objects of sense are determined by reference to
the faculty of sense it is clearly the relation to touch which determines
that which is hard and soft absolutely, and touch is that which we
use as a standard or mean. So we call that which exceeds it hard and
that which falls short of it soft.

Part 5

A body determined by its own boundary must be either hard or soft;
for it either yields or does not.

It must also be concrete: or it could not be so determined. So since
everything that is determined and solid is either hard or soft and
these qualities are due to concretion, all composite and determined
bodies must involve concretion. Concretion therefore must be discussed.

Now there are two causes besides matter, the agent and the quality
brought about, the agent being the efficient cause, the quality the
formal cause. Hence concretion and disaggregation, drying and moistening,
must have these two causes.

But since concretion is a form of drying let us speak of the latter
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« Reply #95 on: August 31, 2009, 12:09:25 am »

As we have explained, the agent operates by means of two qualities
and the patient is acted on in virtue of two qualities: action takes
place by means of heat or cold, and the quality is produced either
by the presence or by the absence of heat or cold; but that which
is acted upon is moist or dry or a compound of both. Water is the
element characterized by the moist, earth that characterized by the
dry, for these among the elements that admit the qualities moist and
dry are passive. Therefore cold, too, being found in water and earth
(both of which we recognize to be cold), must be reckoned rather as
a passive quality. It is active only as contributing to destruction
or incidentally in the manner described before; for cold is sometimes
actually said to burn and to warm, but not in the same way as heat
does, but by collecting and concentrating heat.

The subjects of drying are water and the various watery fluids and
those bodies which contain water either foreign or connatural. By
foreign I mean like the water in wool, by connatural, like that in
milk. The watery fluids are wine, urine, whey, and in general those
fluids which have no sediment or only a little, except where this
absence of sediment is due to viscosity. For in some cases, in oil
and pitch for instance, it is the viscosity which prevents any sediment
from appearing.

It is always a process of heating or cooling that dries things, but
the agent in both cases is heat, either internal or external. For
even when things are dried by cooling, like a garment, where the moisture
exists separately it is the internal heat that dries them. It carries
off the moisture in the shape of vapour (if there is not too much
of it), being itself driven out by the surrounding cold. So everything
is dried, as we have said, by a process either of heating or cooling,
but the agent is always heat, either internal or external, carrying
off the moisture in vapour. By external heat I mean as where things
are boiled: by internal where the heat breathes out and takes away
and uses up its moisture. So much for drying.
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« Reply #96 on: August 31, 2009, 12:09:46 am »

Part 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.
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« Reply #97 on: August 31, 2009, 12:09:59 am »

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.

Part 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.
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« Reply #98 on: August 31, 2009, 12:10:13 am »

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,
there is little or no cheese in milk, and such milk is not nutritive
and is more like water. The case of blood is similar: cold dries and
so solidifies it. Those kinds of blood that do not solidify, like
that of the stag, belong rather to water and are very cold. Hence
they contain no fibres: for the fibres are of earth and solid, and
blood from which they have been removed does not solidify. This is
because it cannot dry; for what remains is water, just as what remains
of milk when cheese has been removed is water. The fact that diseased
blood will not solidify is evidence of the same thing, for such blood
is of the nature of serum and that is phlegm and water, the nature
of the animal having failed to get the better of it and digest it.
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« Reply #99 on: August 31, 2009, 12:10:27 am »

Some of these bodies are soluble, e.g. natron, some insoluble, e.g.
pottery: of the latter, some, like horn, can be softened by heat,
others, like pottery and stone, cannot. The reason is that opposite
causes have opposite effects: consequently, if solidification is due
to two causes, the cold and the dry, solution must be due to the hot
and the moist, that is, to fire and to water (these being opposites):
water dissolving what was solidified by fire alone, fire what was
solidified by cold alone. Consequently, if any things happen to be
solidified by the action of both, these are least apt to be soluble.
Such a case we find where things have been heated and are then solidified
by cold. When the heat in leaving them has caused most of the moisture
to evaporate, the cold so compacts these bodies together again as
to leave no entrance even for moisture. Therefore heat does not dissolve
them (for it only dissolves those bodies that are solidified by cold
alone), nor does water (for it does not dissolve what cold solidifies,
but only what is solidified by dry heat). But iron is melted by heat
and solidified by cold. Wood consists of earth and air and is therefore
combustible but cannot be melted or softened by heat. (For the same
reason it floats in water-all except ebony. This does not, for other
kinds of wood contain a preponderance of air, but in black ebony the
air has escaped and so earth preponderates in it.) Pottery consists
of earth alone because it solidified gradually in the process of drying.
Water cannot get into it, for the pores were only large enough to
admit of vapour escaping: and seeing that fire solidified it, that
cannot dissolve it either.

So solidification and melting, their causes, and the kinds of subjects
in which they occur have been described.

Part 8
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« Reply #100 on: August 31, 2009, 12:10:46 am »

All this makes it clear that bodies are formed by heat and cold and
that these agents operate by thickening and solidifying. It is because
these qualities fashion bodies that we find heat in all of them, and
in some cold in so far as heat is absent. These qualities, then, are
present as active, and the moist and the dry as passive, and consequently
all four are found in mixed bodies. So water and earth are the constituents
of homogeneous bodies both in plants and in animals and of metals
such as gold, silver, and the rest-water and earth and their respective
exhalations shut up in the compound bodies, as we have explained elsewhere.

All these mixed bodies are distinguished from one another, firstly
by the qualities special to the various senses, that is, by their
capacities of action. (For a thing is white, fragrant, sonant, sweet,
hot, cold in virtue of a power of acting on sense). Secondly by other
more characteristic affections which express their aptitude to be
affected: I mean, for instance, the aptitude to melt or solidify or
bend and so forth, all these qualities, like moist and dry, being
passive. These are the qualities that differentiate bone, flesh, sinew,
wood, bark, stone and all other homogeneous natural bodies. Let us
begin by enumerating these qualities expressing the aptitude or inaptitude
of a thing to be affected in a certain way. They are as follows: to
be apt or inapt to solidify, melt, be softened by heat, be softened
by water, bend, break, be comminuted, impressed, moulded, squeezed;
to be tractile or non-tractile, malleable or non-malleable, to be
fissile or non-fissile, apt or inapt to be cut; to be viscous or friable,
compressible or incompressible, combustible or incombustible; to be
apt or inapt to give off fumes. These affections differentiate most
bodies from one another. Let us go on to explain the nature of each
of them. We have already given a general account of that which is
apt or inapt to solidify or to melt, but let us return to them again
now. Of all the bodies that admit of solidification and hardening,
some are brought into this state by heat, others by cold. Heat does
this by drying up their moisture, cold by driving out their heat.
Consequently some bodies are affected in this way by defect of moisture,
some by defect of heat: watery bodies by defect of heat, earthy bodies
of moisture. Now those bodies that are so affected by defect of moisture
are dissolved by water, unless like pottery they have so contracted
that their pores are too small for the particles of water to enter.
All those bodies in which this is not the case are dissolved by water,
e.g. natron, salt, dry mud. Those bodies that solidified through defect
of heat are melted by heat, e.g. ice, lead, copper. So much for the
bodies that admit of solidification and of melting, and those that
do not admit of melting.

The bodies which do not admit of solidification are those which contain
no aqueous moisture and are not watery, but in which heat and earth
preponderate, like honey and must (for these are in a sort of state
of effervescence), and those which do possess some water but have
a preponderance of air, like oil and quicksilver, and all viscous
substances such as pitch and birdlime.
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« Reply #101 on: August 31, 2009, 12:11:09 am »

Part 9

Those bodies admit of softening which are not (like ice) made up of
water, but in which earth predominates. All their moisture must not
have left them (as in the case of natron and salt), nor must the relation
of dry to moist in them be incongruous (as in the case of pottery).
They must be tractile (without admitting water) or malleable (without
consisting of water), and the agent in softening them is fire. Such
are iron and horn.

Both of bodies that can melt and of bodies that cannot, some do and
some do not admit of softening in water. Copper, for instance, which
can be melted, cannot be softened in water, whereas wool and earth
can be softened in water, for they can be soaked. (It is true that
though copper can be melted the agent in its case is not water, but
some of the bodies that can be melted by water too such as natron
and salt cannot be softened in water: for nothing is said to be so
affected unless the water soaks into it and makes it softer.) Some
things, on the other hand, such as wool and grain, can be softened
by water though they cannot be melted. Any body that is to be softened
by water must be of earth and must have its pores larger than the
particles of water, and the pores themselves must be able to resist
the action of water, whereas bodies that can be 'melted' by water
must have pores throughout.

(Why is it that earth is both 'melted' and softened by moisture, while
natron is 'melted' but not softened? Because natron is pervaded throughout
by pores so that the parts are immediately divided by the water, but
earth has also pores which do not connect and is therefore differently
affected according as the water enters by one or the other set of
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« Reply #102 on: August 31, 2009, 12:11:24 am »

Some bodies can be bent or straightened, like the reed or the withy,
some cannot, like pottery and stone. Those bodies are apt to be bent
and straightened which can change from being curved to being straight
and from being straight to being curved, and bending and straightening
consist in the change or motion to the straight or to a curve, for
a thing is said to be in process of being bent whether it is being
made to assume a convex or a concave shape. So bending is defined
as motion to the convex or the concave without a change of length.
For if we added 'or to the straight', we should have a thing bent
and straight at once, and it is impossible for that which is straight
to be bent. And if all bending is a bending back or a bending down,
the former being a change to the convex, the latter to the concave,
a motion that leads to the straight cannot be called bending, but
bending and straightening are two different things. These, then, are
the things that can, and those that cannot be bent, and be straightened.

Some things can be both broken and comminuted, others admit only one
or the other. Wood, for instance, can be broken but not comminuted,
ice and stone can be comminuted but not broken, while pottery may
either be comminuted or broken. The distinction is this: breaking
is a division and separation into large parts, comminution into parts
of any size, but there must be more of them than two. Now those solids
that have many pores not communicating with one another are comminuible
(for the limit to their subdivision is set by the pores), but those
whose pores stretch continuously for a long way are breakable, while
those which have pores of both kinds are both comminuible and breakable.
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« Reply #103 on: August 31, 2009, 12:11:42 am »

Some things, e.g. copper and wax, are impressible, others, e.g. pottery
and water, are not. The process of being impressed is the sinking
of a part of the surface of a thing in response to pressure or a blow,
in general to contact. Such bodies are either soft, like wax, where
part of the surface is depressed while the rest remains, or hard,
like copper. Non-impressible bodies are either hard, like pottery
(its surface does not give way and sink in), or liquid, like water
(for though water does give way it is not in a part of it, for there
is a reciprocal change of place of all its parts). Those impressibles
that retain the shape impressed on them and are easily moulded by
the hand are called 'plastic'; those that are not easily moulded,
such as stone or wood, or are easily moulded but do not retain the
shape impressed, like wool or a sponge, are not plastic. The last
group are said to be 'squeezable'. Things are 'squeezable' when they
can contract into themselves under pressure, their surface sinking
in without being broken and without the parts interchanging position
as happens in the case of water. (We speak of pressure when there
is movement and the motor remains in contact with the thing moved,
of impact when the movement is due to the local movement of the motor.)
Those bodies are subject to squeezing which have empty pores-empty,
that is, of the stuff of which the body itself consists-and that can
sink upon the void spaces within them, or rather upon their pores.
For sometimes the pores upon which a body sinks in are not empty (a
wet sponge, for instance, has its pores full). But the pores, if full,
must be full of something softer than the body itself which is to
contract. Examples of things squeezable are the sponge, wax, flesh.
Those things are not squeezable which cannot be made to contract upon
their own pores by pressure, either because they have no pores or
because their pores are full of something too hard. Thus iron, stone,
water and all liquids are incapable of being squeezed.
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« Reply #104 on: August 31, 2009, 12:11:58 am »

Things are tractile when their surface can be made to elongate, for
being drawn out is a movement of the surface, remaining unbroken,
in the direction of the mover. Some things are tractile, e.g. hair,
thongs, sinew, dough, birdlime, and some are not, e.g. water, stone.
Some things are both tractile and squeezable, e.g. wool; in other
cases the two qualities do not coincide; phlegm, for instance, is
tractile but not squeezable, and a sponge squeezable but not tractile.

Some things are malleable, like copper. Some are not, like stone and
wood. Things are malleable when their surface can be made to move
(but only in part) both downwards and sideways with one and the same
blow: when this is not possible a body is not malleable. All malleable
bodies are impressible, but not all impressible bodies are malleable,
e.g. wood, though on the whole the two go together. Of squeezable
things some are malleable and some not: wax and mud are malleable,
wool is not. Some things are fissile, e.g. wood, some are not, e.g.
potter's clay. A thing is fissile when it is apt to divide in advance
of the instrument dividing it, for a body is said to split when it
divides to a further point than that to which the dividing instrument
divides it and the act of division advances: which is not the case
with cutting. Those bodies which cannot behave like this are non-fissile.
Nothing soft is fissile (by soft I mean absolutely soft and not relatively:
for iron itself may be relatively soft); nor are all hard things fissile,
but only such as are neither liquid nor impressible nor comminuible.
Such are the bodies that have the pores along which they cohere lengthwise
and not crosswise.

Those hard or soft solids are apt to be cut which do not necessarily
either split in advance of the instrument or break into minute fragments
when they are being divided. Those that necessarily do so and liquids
cannot be cut. Some things can be both split and cut, like wood, though
generally it is lengthwise that a thing can be split and crosswise
that it can be cut. For, a body being divided into many parts fin
so far as its unity is made up of many lengths it is apt to be split,
in so far as it is made up of many breadths it is apt to be cut.
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