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LECTURE I.
Of Matter and Motion.
By Matter, my dear friends, we mean the substance of all things, or that of
which all bodies are composed, in what
ever form or manner they may present
themselves to our senses: for this top, Tom Wilson's ivory ball, the hill before us,
that orange on the table, and all
things you see, are made of matter differently
formed.
As to Motion, I may save myself and
you the trouble of explaining that; for
every boy who can whip his top knows what
motion is as well as his master.
Matter, or Body, is indifferent to motion or rest. As for example, now I whip my
top, and it runs round, or is in motion;
but when I no longer whip it, the top
falls down, as you see, and is at rest.
When a body is in motion, as much force is required to make it rest, as was requiredrequired, while it was at rest, to put it in motion. Thus, suppose a boy strikes a
trap-ball with one hand, and another stands
close by to catch it with one of his hands,
it will require as much strength or force
to stop that ball, or put it in a state of rest,
as the other gave to put it in motion;
allowing for the distance the two boys
stand apart.
No body or part of matter can give itself either motion or rest: and therefore a
body at rest will remain so for ever, unless
it be put in motion by some external cause;
and a body in motion will move for ever,
unless some external cause stops it.
This seemed so absurd to Master Wilson,
that he burst into a loud laugh. What,
says he, shall any body tell me that my
hoop or my top will run for ever, when I
know by daily experience that they drop
of themselves, without being touched by
any body? At which our little Philosopher
was angry, and having commanded silence,
Don't expose your ignorance, Tom Wilson,
for the sake of a laugh, says he: if you
intend to go through my Course of Phi
losophy, and to make yourself acquainted
with the nature of things, you must pre
than this. When you say that nothing
touched the top or the hoop, you forget
their friction or rubbing against the ground
they run upon, and the resistance they
meet with from the air in their course,
which is very considerable though it has
escaped your notice. Somewhat too might
be said on the gravity and attraction be
tween the top or the hoop, and the earth;
but that you are not yet able to compre
hend, and therefore we shall proceed in
our Lecture.
A body in motion will always move on in a strait line, unless it be turned out of it by some external cause. Thus we see
that a marble shot upon the ice, if the
surface be very smooth, will continue its
motion in a strait line, till it is put to rest
by the friction of the ice and air, and the
force of attraction and gravitation.
The swiftness of motion is measured by distance of place, and the length of time in which it is performed. Thus if a
cricket-ball and a fives-ball move each of
them twenty yards in the same time, their
motions are equally swift; but if the fives-
ball moves two yards while the cricket-ball
fives-ball twice as swift as the other.
But the quantity of motion is measured by the swiftness of motion, as above described, and the quantity of matter moved considered together. For instance, if the
cricket-ball be equal in bulk and weight
to the fives-ball, and move as swift, then
it hath an equal quantity of motion. But
if the cricket-ball be twice as big and as
heavy as the fives-ball, and yet moves
equally swift, it hath double the quantity
of motion; and so in proportion.
All bodies have a natural tendency, attractions, or gravitation towards each other.
Here Tom Wilson, again laughing, told the
Company that Philosophy was made up of
nothing but hard words. That is because
you have not sense enough to enquire into,
and retain the signification of words, says
our Philosopher. All words, continued
he, are difficult till they are explained;
and when that is done, we shall find that
gravity or gravitation will be as easily
understood as praise or commendation,
and attraction as easily as correction;
which you deserve, Tom Wilson, for your
impertinence.
Gravity, my dear friends, is that universal disposition of matter which inclines or carries the lesser part towards the centre of the greater part; which is called weight or gravitation in the lesser body, but at
traction in the greater, because it draws, as it were, the lesser body to it. Thus all bodies on or near the earth's surface have
a tendency, or seeming inclination, to des
cend towards it middle or centre;
and but for this principle in nature, the
earth (considering its form and situation
in the universe) could not subsist as it is:
for we all suppose the earth to be nearly
round, (nay we are sure it is so, for my
Lord Anson and many other gentlemen,
you know, have sailed around it) and as it
is suspended in such a mighty void or
space and always in motion, what should
hinder the stones, water, and other parts
of matter falling from the surface, but the
almighty arm of God, or this principle or
universal law of nature, of attraction and
gravitation, which he has established to
keep the universe in order. To illustrate
and explain what I have said, let us sup
pose the following figure to be the earth
and seas. Let Tom Wilson stand at this
point of the globe or earth where we are, Hal Thompson at the opposite part of
the earth, with his feet (as they must be)
towards us: if Tom drop an orange out of
his hand, it will fall down towards Hal;
and if Hal drop an orange, it will fall
seemingly upwards (if I may so express
myself) towards Tom: and if these oranges
had weight and power sufficient to displace
the other particles of matter of which the
earth is composed, so as to make way to
the centre, they would there unite toge
ther and remain fixed; and they would
then lose their power of gravitation, as be
ing at the center of gravity and unable to
This occasioned a general laugh; and Tom Wilson starting up, asked how Master Thompson was to stand with his feet up
wards, as here represented, without hav
ing anything to support his head? Have
patience, says the little Philosopher, and I
will tell you; but pray behave with good
manners, Master Wilson, and don't laugh
at every thing you cannot comprehend.
This difficulty is solved, and all the seem
ing confusion which you apprehend of bo
dies flying off from each other is removed,
by means of this attraction and gravita
tion. Ask any of the sailors who have
been around the world, and they will tell
you that the people on the part of the
globe over-against us do not walk upon
their heads, though the earth is round;
and though their heels are opposite ours,
they are in no more danger of falling into
the mighty space beneath them, than we
are of falling (or rather rising I must call
it here) up to the moon or the stars.
But besides this general law of attraction
and gravitation, which affects all bodies
equally and universally, there are parti
cular bodies that attract and repel Magnet or Loadstone, which has not only the property
of directing the nedle of the mariner's
compass when touched with it to the north,
but also of attracting or bringing
iron to it with one end, and repelling or
forcing it away with the other end: and Sam Jones's knife, which was whet on a
Loadstone some years ago, still retains the
power you see of picking up needles and
small pieces of iron.
Glass, Sealing-Wax, Amber, and Precious Stones, when chafed or rubbed till they
are warm, will likewise both attract and
repel feathers, hairs, straw &c. which is
sufficient to prove that each of these bodies
has a sphere of arractiuopm assined it, be
yond which it will repel the same body it
would otherwise attract.
When bodies are so attracted by each
other as to be united or brought into close
contact, they then adhere or cohere toge
ther so as not to be easily separated, and
this is called in Philosophy the Power of Cohesion, and is undoubtedly that principle
which binds large bodies together; for all
large bodies are made up of atoms or par
ticles inconceivably small. And this co
hesion will always be proportioned to the
face of bodies that come into contact or
touch each other: for those bodies that
are of spherical form will not adhere so
strongly as those that are flat or square;
because they can only touch each other
at a certain point; and this is the reason why
the particles of water and quicksilver,
which are globular or round, are so easily
separated with a touch, while those
of metals and some other bodies are not to be
parted but with great force. To give us
a familiar instance of this cohesion of mat
ter, our Philosopher took two leaden balls,
and filing a part off each so that the two
flat parts might come into close contact,
he gently pressed them together and they
united so firmly that it required consider
able force to get them asunder.
One thing I must tell you of magnetism,
which seems pretty extraordinary. Master Brown took his uncle's sword, and sup
ported it with the point downwards, by
resting the shell of the hilt on the top of
his two forefingers; and Master Smith was
placed with his father's amber-headed
cane at about three or four feet distance,
where he kept rubbing the amber head
round on his waistcoat. After some little
distance; and some time after that it turn
ed quite round; but was soon turned back
again by master 's rubbing the am
ber head backwards, or in a contrary di
rection
But what seems most worthy of our ad
miration is the Electrical Fire, which so
plentifully abounds in the universe, and
which is excited, or made visible, by the
friction or rubbing of a glass globe. This
fire, by a very simple machine, may be con
veyed into the human body, every part
of which it pervades in an instant, and is
said to have been very serviceable in the
cure of some disorders. It may be drawn
from the ladies eyes, yet it leaves them no
less brilliant than they were before. It
may be drawn from under thunder-clouds, and
is probably the same species of fire with
the lightening; for Professor Richmann of Hamburgh>, who fixed a machine to bring it
down from the clouds in large quantities,
was killed by the stroke it gave him.
The same force aplied to two different bodies will always produce the same quantity of motion in each of them. To prove this,
we put Master Jones into a boat, which
(including his own weight) weighed ten Thames by the Mill-bank;
and on the Lambeth side, just opposite, we
placed another boat (of one hundred
weight) with a string tied to it. This
string Master Jones pulled in the other
boat; and we observed that as the boats
approached each other, the small boat
moved ten feet for every foot the other
moved: which proves what we have before
observed as to the quantity of motion.
Attraction is the stronger, the nearer the attracting bodies are to each other; and in different distances of the same bodies it decreases as the squares of the distances between the centres of those bodies increase.
For if two bodies at a given distance at
tract each other with a certain force, at
half the distance they will attract each
other with four times that force. But this
I shall further explain in my next course of Lectures.
Two bodies at a distance will put each other into motion by the force of Attraction or Gravitation. This we know to
be true by experience, though we cannot
account for it; and therefore it is to be
received as a principle in Natural Phi
losophy.