[Illustration]
[Illustration: Frontispiece]
WONDERS OF PHYSICAL SCIENCE
=Readable Books in Natural Knowledge=
Globe 8vo.
WONDERS OF PHYSICAL SCIENCE. By
E. E. FOURNIER, B.Sc.
TILLERS OF THE GROUND. By Marion
I. NEWBIGIN, D.Sc.
THREADS IN THE WEB OF LIFE. By
Professor J. ARTHUR THOMSON, M.A., and
MARGARET R. THOMSON.
_And others to follow._
MACMILLAN AND CO., LTD., LONDON.
=Readable Books in Natural Knowledge=
WONDERS OF PHYSICAL SCIENCE
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MACMILLAN AND CO., Limited
LONDON • BOMBAY • CALCUTTA
MELBOURNE
THE MACMILLAN COMPANY
NEW YORK • BOSTON • CHICAGO
ATLANTA • SAN FRANCISCO
THE MACMILLAN CO. OF CANADA, Ltd.
TORONTO
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WONDERS OF
PHYSICAL SCIENCE
BY
E. E. FOURNIER, B.Sc.
ASSOCIATE OF ROYAL COLLEGE OF SCIENCE, LONDON
To try things oft, and never to give over, doth wonders.--BACON.
MACMILLAN AND CO., LIMITED
ST. MARTIN’S STREET, LONDON
1910
PUBLISHERS’ NOTE
SO much attention is now given to the practical and systematic study
of science in schools that the valuable influence of descriptive
scientific literature is apt to be overlooked. An intimate knowledge
of the simplest fact in Nature can be obtained only by personal
observation or experiment in the open air or the laboratory, but broad
views of scientific thought and progress are secured best from books in
which the methods and results of investigation are stated in language
which is simple without being childish.
Books intended to promote interest in science must differ completely
from laboratory guides, text-books, or works of reference. They should
aim at exalting the scientific spirit which leads men to devote their
lives to the advancement of natural knowledge, and at showing how the
human race eventually reaps the benefit of such research. Inspiration
rather than information should be the keynote; and the execution should
awaken in the reader not only appreciation of the scientific method of
study and spirit of self-sacrifice, but also a desire to emulate the
lives of men whose labours have brought the knowledge of Nature to its
present position.
These are the objects of the series of Readable Books in Natural
Knowledge to which the present volume belongs. Each volume will
endeavour to stimulate interest in the studies with which it is
concerned, and to present natural phenomena and laws broadly and
attractively. It is hoped that the books will provide the reading
matter urgently required in connection with the science work in
schools and will appeal also to a wide circle of other readers. The
series should be of service in directing attention to the nobility of
scientific ideals and the ultimate value of results obtained by careful
and faithful work.
CONTENTS
CHAP. PAGE
1. ARCHIMEDES 1
2. THE WISE MEN OF ALEXANDRIA 11
3. ARABIAN DAYS 22
4. DR. GILBERT OF COLCHESTER 34
5. GALILEO 50
6. THE BAROMETER 65
7. THE AIR-PUMP 80
8. THE INVENTOR OF THE STEAM-ENGINE 88
9. ELECTRIC SPARKS 100
10. THE ELECTRIC CURRENT 113
11. THE ELECTRIC TELEGRAPH 124
12. THE TELEPHONE 136
13. ELECTRIC LIGHT 149
14. MICHAEL FARADAY 159
15. TELEGRAPHING WITHOUT WIRES 170
16. THE NEW RAYS 178
17. AIR-SHIPS AND FLYING MACHINES 190
CHAPTER I
ARCHIMEDES
THE land of Italy is shaped like a boot, and at the toe of
the boot lies a three-cornered island called Sicily. It was famous
in ancient times for its cities, temples, and palaces; for its
fruit-gardens and cornfields; and for its great volcano called Etna,
from the top of which a cloud of steam and dust ascends, and sometimes
a fiery stream of molten rock flows down.
Sicily has often been shaken by earthquakes, but the worst of all was
the earthquake which destroyed the town of Messina at Christmas 1908.
The greatest city of Sicily was called Syracuse. It is now a town of
25,000 inhabitants, built on an island joined to the mainland by a
bridge. But in ancient times it had ten times as many people, and its
buildings covered the heights and cliffs opposite, and extended along
the banks of the river, up to where the papyrus plants grow, which the
ancients made into paper.
In that great city dwelt a man called Archimedes. He was a rich and
wise man, a friend and relative of the king, and had he chosen, he
could have spent all his days in the pursuit of pleasure, going to the
races and matches and theatres, and dining every day at the king’s
table. But his mind was given to the pursuit of science and of truth.
His great delight lay in studying the laws of Nature, and finding
out the secrets of her working. He believed that everything happens
according to some law or principle, and that if once he could discover
the law he could rule the world.
Archimedes was born 300 years before Christ. When he was young, war was
raging in Sicily between the Greeks and Romans and the people of the
city of Carthage in Africa, each wishing to possess the beautiful and
fertile island. The king of Syracuse joined the Romans, and as they
proved the strongest, he was able to reign in peace for fifty years.
During that time the trade and commerce of the city flourished. The
king built many ships, some of them larger than any seen before, and
these ships sailed to Egypt and Greece, Africa and Spain, and along the
coasts of France and Italy, exchanging grain and fruit for purple and
gems, Arabian horses, and amber from the shores of the Baltic.
Archimedes spent much of his time in the harbour and in the
shipbuilding yards, watching the sailors and shipwrights at their
work, and helping them with his new inventions. He saw them lift heavy
weights, and taught them how to do it without great exertion. They
already knew how to use a lever, or crowbar, for lifting heavy stones.
They pushed the end of the lever under the stone, and rested the lever
or bar on another stone close to it.
[Illustration: Fig. 1.--A Lever to move the Earth.]
In that way they could exert a great force. Archimedes measured the
force they could exert in this way, and found it was increased when
the bar was made longer and the distance between the stone and the
support was made less. When the distance between the support and the
hand was five times the distance between the support and the stone,
Archimedes found that the force of the hand was multiplied by five,
and one man could lift a stone which it would take five men to lift
without a lever. “Now,” he said, “if you make the lever long enough
there is no weight too heavy for us to lift.” He told the king about
this discovery, and said to him, “If you gave me some place on which
to stand, I could move the whole earth.”
[Illustration: Fig. 2.--The Endless Screw.]
Archimedes knew, of course, that the matter was not quite so simple
as that. He knew that the lever required to move the earth would have
to be exceedingly stout and strong, as thick, indeed, as the earth
itself. For, otherwise, it would not stand the strain. Besides, he
knew he would also require a fixed support against which to rest the
lever. And the place on which he was to stand would have also to be
firmly fixed, so as to allow him to exert the force required. We know
now that the earth floats freely in space, and that there is no fixed
place anywhere. Therefore we cannot, after all these 2200 years, try
the great experiment suggested by Archimedes.
But many other things which Archimedes proposed are now used every day.
One of these is the Endless Screw, by means of which Archimedes is said
to have drawn a ship, with cargo and crew, along the sand as easily as
if it were floating in water, to the great delight of his friend the
king.
Not long after this the king showed Archimedes a great mark of favour
and confidence. This is how it came about.
[Illustration: Fig. 3.--Archimedes’ Screw can be used to raise Water.]
The king had given one of his goldsmiths a certain weight of gold,
and instructed him to make it into a golden crown which he wanted to
present to one of the temples. After a few weeks the goldsmith came
to the palace and brought the crown to the king. The king weighed the
crown, and found it was the same weight as the gold he had given out.
But somebody told him that the goldsmith had mixed a quantity of silver
with the gold, and kept the remaining gold for himself.
The king was a just man, and did not want to accuse the goldsmith of
the crime without having a proof of his guilt. He therefore sent for
Archimedes and gave him the crown, asking him to find out whether any
silver had been mixed with the gold, or whether it was made of pure
gold.
Archimedes was long puzzled over this problem. He weighed the crown,
and found the weight was correct. It also looked like pure gold, so
that the amount of silver could not be very much. Archimedes made
two blocks, one of silver and the other of gold, of exactly the same
size, and found that the block of gold weighed nearly twice as much as
the block of silver. “Now,” he said to himself, “if I could melt up
the crown and make it into a square block, and make another block of
exactly the same size of pure gold, both should weigh the same if the
crown is pure gold, but if it is not, the block made from the crown
should be lighter.” He wished for a moment to melt up the crown, but it
was beautifully made, and he thought it a pity to throw away the fine
work. If he could only find out the exact bulk of the crown, he thought
he could determine easily if it was the proper weight which it should
be if made of pure gold. The problem then was how to find out the total
bulk of the crown without melting it up into a block.
Archimedes was in the habit of following up a problem steadily until he
had solved it. He allowed nothing to come in the way. Sometimes he was
found tracing lines and circles in the ashes of the grate, working out
some problem. Sometimes, even, when he had had his bath, and his slaves
had rubbed him with oil to make his skin smooth, he traced diagrams
with his fingers on the layer of oil on his skin. He could think of
nothing but the problem he was trying to solve.
The problem of the crown puzzled him greatly; but one day the solution
flashed upon him just as he was having his bath. He was taking a bath
in a kind of large cup of his own size, as the Greeks used to do. The
cup stood on a pedestal, with a sink round it to let the water flow
off. When he got in, the cup was full of water to the brim, therefore
it overflowed as he was getting in. He dipped himself entirely under
water, head and all, and when he got out again the water was no longer
up to the brim, but considerably below it. _The amount of water which
had flowed out was exactly the bulk of his own body_. The truth came
upon Archimedes like a flash. He had found a way of determining the
bulk of his own body without melting himself down into a block, and why
should he not find the bulk of the crown in the same manner?
He was so excited that he forgot to dry and clothe himself, but ran
home just as he was, calling out, “I have found it! I have found it!”
He took a big jug full of water to the brim, and carefully let down the
crown into it, holding it by a thread. A quantity of water overflowed,
and when the crown was taken out the water was on a lower level. He
took a measuring glass, and carefully measured how much water was
required to bring the water up to the brim again. That quantity of
water had the same bulk as the crown.
He then measured out a quantity of gold and a quantity of silver, both
quantities weighing exactly the same as the crown. These quantities
he melted up into blocks. In this manner he got three things weighing
exactly the same: a block of gold, a block of silver, and the crown
which the goldsmith had made. He then dipped the gold block into
the jug filled to the brim. It displaced a certain amount of water.
Again, he dipped the silver block into the jug. It displaced nearly
twice as much water. Finally, he dipped the crown into the full jug.
It displaced more water than the gold block, but less water than the
silver block. And so it was proved that _the crown contained a
quantity of silver_.
Archimedes next made some other blocks, containing gold mixed with
various proportions of silver, but always of the same weight as
the crown. In the end he obtained a block of silver and gold which
displaced exactly as much water as the crown. He went to the king and
told him exactly how much silver was in the crown, and how much gold
the goldsmith had stolen.
The king thanked his clever friend. He sent for the goldsmith and told
him he had found him out. The goldsmith confessed his guilt, and the
king made him restore the gold and kept him in prison until he had been
justly punished for his crime.
Archimedes continued his experiments with all sorts of bodies and
substances.
[Illustration: Fig. 4.--An Archimedes Cup.]
He weighed things in air and in water, and found that when
they were suspended in water by a thread, and the thread was attached
to one arm of a balance, the weight necessary to counterbalance it
was less than when the body hangs in air. The difference in the
counterbalancing weight is equal to the weight of the water which the
body displaces. This may be proved by a simple experiment.
A glass beaker with a spout, like that in Fig. 4, has water poured
into it until the water just runs out of the spout. The beaker with
the water in it is placed in one pan of a balance, and weights are put
in the other pan until the balance is even. A block of wood is then
weighed and floated on the water in the cup. Some of the water flows
out of the spout and may be caught in another beaker. But when the cup
is weighed with the floating block it is found that the weight is
exactly the same as before. The wood exerts no additional weight, since
its weight is equal to that of the water which flowed over, as may be
proved by weighing the water caught in the small beaker. Archimedes put
this rule into a few words as follows: “Every body loses as much weight
in water as the displaced water weighs.” This is called the Principle
of Archimedes.
[Illustration: Fig. 5.--Ancient. War-Engine for throwing Rocks.]
When, after fifty years’ peace, the Romans made war on Syracuse,
Archimedes took charge of the defence of the city. He made great
war-engines which threw rocks upon the attacking army, and sank the
enemy’s ships in the harbour. Marcellus, the Roman general, could not
help admiring the genius of the great Syracusan engineer, and when he
captured the city at last he ordered his soldiers to spare Archimedes.
One of them came upon the great inventor just as he was working out a
problem with a stick in the sand on the floor. When the soldier asked
his name, he told him to wait till he had solved the problem, and not
to tread upon his circles. Thereupon the soldier killed him.
Marcellus was greatly grieved, and tried to atone for this by showing
great kindness to the relatives.
Archimedes was buried near the city. On his grave was put a monument
in the shape of a cylinder enclosing a ball or sphere. It was one of
his proudest achievements to find that a ball enclosed in a cylinder of
the same height fills up just two-thirds of its bulk. No more suitable
device could have been placed on the grave of one of the greatest men
of science that ever lived.