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Pages of Meteorology

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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



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


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 first.

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

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