439 Polarity,

110 Scab in sheep,

403

411SH GRAMMAR,

1343

German costumes,

562 Interjection, the,

196

Gd Gas manufacture,

GEOMETRY,

665 Inference,

666 Inflection,

476 Inks,

49

Hot water apparatus,

659

544

Hours,

593

248 House on fire,

644

683

646

406 House-keeping,

647

40 Human figure drawing,

232

Ploughs,

127 Plum, the,

Pneumatics,

Poison, reinedies for,
Polarity,

71 Platinum,

639

61

439

266 Pine and fir, the,

78 Planetariums,

46

Plantations, ornamental,

450 Plants, propagation of,

739 Plate,

744 Plate-glass,

601 Safety-cape,

405 Salads,

372 Salt,

647 Salts,

762 Salt-mines,
79 Saltpetre,

324 Salmon-fishing,

305 Sand-glasses,

42 Savings'-banks,

110 Scab in sheep,

402

643

362

96

71

751

525

645 Saxon architecture,

NUMBER 51.

PRICE 14d.

NATURAL PHILOSOPHY is a term of wide import, and has
a reference to all those branches of physical science
which treat of existing substances, their motions, their
mutual connexion, and their influence on each other.
In this enlarged sense it may be considered as embrac-
ing astronomy, mathematics, dynamics, hydrostatics,
geology, chemistry, opties, botany, in short, a vast range
of human knowledge, which for the sake of convenience
is usually divided into distinct branches of science. In
its more limited and ordinary meaning, the term applies
only to inorganic substances, and the laws which regu-
late their connexion with each other, but without alte-
ration of character; and it is this most important branch
of knowledge, which in reality is the basis of all others,
of which we now propose treating. We shall commence
with an explicit definition of the meaning of the term
substances or matter, it being necessary that this be
clearly understood.

MATTER AND ITS PROPERTIES.

Matter-or that of which all bodies are composed
whose existence is made known to us by means of the
senses or by the test of philosophic experiment-is pos-
sessed of various properties, some of which are essential
to its existence, while others are only accidental or con-
tingent. The essential properties of matter are Im-
penetrability, Extension, Figure, Divisibility, Inertia,
and Attraction.

Impenetrability is that quality of bodies, in virtue of
which each occupies a certain portion of space, and ex-
cludes other bodies from existing in the same place at
the same instant. In the usual sense, we call any hard
body, such as a stone, impenetrable, because it firmly
resists our efforts to pierce it. But as it is understood
philosophically (although we can condense, pierce, and
remove the greater number of them), all bodies are
alike impenetrable, because they equally possess the
property of excluding other substances from the spaces
which they occupy. This, in fact, is saying no more
than that two things cannot be in the same place at
once, which is a self-evident truth, whether we apply
it to a single particle of matter or a large mass.

Every body, or portion or particle of matter, pos-
sesses a certain extension or magnitude. It is impos-
sible to form a conception of matter, however minute
may be the particle, without connecting with it the idea
of its having a certain bulk, and filling a certain extent
of space. In common phraseology, we express this pro-
perty of bodies by the word size or volume.

The next property demanding our attention is the
figure of bodies. Figure or form is the result of ex-
tension, for we cannot have the idea of a body possess
ing length and breadth, without its having some kind
of figure, however irregular. The volume of a body
has no relation to its figure. Bodies which have the
zame figure may possess very different volumes; and

bodies may have the same volume, but possess very
different figures. Thus, two masses of matter may have
the same volume, although the one be round and the
other be square.

Matter is divisible into parts, and these parts may
again be subdivided into other parts. By this is meant
divisibility or separability. To the practical subdivision
of matter there seems to be no assignable limit; and
many of the instances of it which may be found in phi-
losophical investigations almost exceed credibility. The
thinnest part of a soap-bubble, which is a thin shell of
water and the matter of soap, does not exceed in thick-
ness the 2,500,000th part of an inch. The useful arts,
also, furnish many striking examples; but it is in the
organised world that the most astonishing proofs of the
extreme divisibility of globules, or particles of matter,
are to be found.

Animalcules that is, animals which are so small as
to be invisible to the naked eye, and which, by means
of microscopes, are seen floating in water-are in some
cases so minute, that it would require a million of them
to form the bulk of a grain of sand. As these animal-
cules possess, in every case, a perfect organisation to
enable them to perform all the functions of life, the
smallness of their different parts, and the extreme
minuteness of the particles of matter which compose
them, are too exquisite to be made the subject of cal-
culation: the imagination is lost in the contemplation
of their wonderful economy. The effluvium or odour
which excites the sensation of smell, consists of an in-
calculable number of particles of matter floating in the
atmosphere, and so minute as to be altogether invisible
to the eye. These particles are not more remarkable
for their inconceivably small size than for the length
of time which they will remain in suspension in the
atmosphere, or in connexion with some particular place.
The effluvium given forth by a single grain of musk has
been known to perfume a large apartment for twenty
years, and yet at the expiry of that period there was no
sensible diminution of the little mass of matter from
which the smell had proceeded.

The diffusion of particles of matter invisible to the
naked eye, is also obvious in the case of the melting of
a piece of sugar in our tea; the solid mass of the sugar
disappears, and the particles of which it was composed
are diffused in the liquid. There is a similar diffusion
of particles of salt in the ocean. When we look through
a glass full of sea water, we perceive that it is pure and
limpid; but if we pour the water into a vessel on the
fire, and boil it, we shall at length discover that, while
the liquid has escaped in the form of vapour, the par-
ticles of salt it held in solution remain incrusted on the
vessel.

Particles of matter are never destroyed or lost, al-
though they may disappear from our immediate obse
vation. Under certain circumstances, the particl