ready to welcome the young scientist. He was known as a man of a very
original turn of mind, and therefore one who would be apt to clash
with those who clung to their belief in the old order of thought. At
last, however, he succeeded in obtaining the chair of Professor of
Mathematics at the University of Padua, then one of the greatest seats
of learning in Italy. Here again he showed the great scope of his
knowledge, and wrote on military architecture and fortifications, the
laws of motion, of the sphere, and various branches of mechanics. He
invented a machine for raising water, and was granted a patent which
secured him his rights in it for twenty years, and he also produced
what he called his Geometrical and Military Compass, but what was
later commonly known as the Sector.
Galileo’s fame as a teacher had now spread widely throughout Europe,
and students began to flock to Padua to study under him. He had a
large house, where a number of his private pupils lived with him, a
garden, in which he delighted, and a workshop. Here he experimented on
his next invention, that of the air thermometer. One of his friends,
Castelli, wrote of this in a letter many years later, dated 1638. “I
remember,” he writes, “an experiment which our Signor Galileo had
shown me more than thirty-five years ago. He took a small glass bottle
about the size of a hen’s egg, the neck of which was two palms long,
and as narrow as a straw. Having well heated the bulb in his hand, he
inserted its mouth in a vessel containing a little water, and,
withdrawing the heat of his hand from the bulb, instantly the water
rose in the neck more than a palm above its level in the vessel. It
is thus that he constructed an instrument for measuring the degrees of
heat and cold.”
In 1604 the attention of all the astronomers of Europe was attracted
by a new star which suddenly appeared in the constellation
Serpentarius. Galileo studied it, and shortly began to lecture on the
comparatively new science of astronomy. Formerly he had taught the old
system of Aristotle to his classes, now, after a searching
investigation, he declared his belief in the contrary conclusions of
Copernicus. This study led him on and on. He became interested in the
magnetic needle, and its use as a compass in navigation. Columbus’
discovery of its changing its position according to its relation to
the North Pole took place on his first voyage to America, and reports
of this had reached Padua. All educated men were rousing to the fact
that the age was fertile with new discoveries in every branch of
knowledge, and Galileo and those who were working with him gave eager
heed to each month’s batch of news.
Mere chance is said to have brought about the making of the first
telescope. The story goes that an apprentice of Hans Lipperhey, an
optician of Middleburg, in Holland, was, one day in October, 1608,
playing with some spectacle lenses in his master’s shop. He noticed
that by holding two of the lenses in a certain position he obtained a
large and inverted view of whatever he looked at. He told Master Hans
about this, and the optician fixed two lenses in a tube, and looking
at the weathercock on a neighboring steeple saw that it seemed much
nearer and to be upside down. He hung the tube in his shop as a
curious toy, and one day the Marquis Spinola examined it and bought it
to present to Prince Maurice of Nassau. Soon a number of Hans
Lipperhey’s scientific neighbors were trying to make copies of his
tube, and before very long reports of it were carried to Italy. The
news reached Galileo while on a visit to Venice in June, 1609. This is
his account of what followed, taken from a letter written to his
brother-in-law Landucci, and dated August 29, 1609.
[Illustration: GALILEO’S TELESCOPE]
“You must know then that about two months ago a report was spread here
that in Flanders a spy-glass had been presented to Prince Maurice, so
ingeniously constructed that it made the most distant objects appear
quite near, so that a man could be seen quite plainly at a distance of
two miles. This result seemed to me so extraordinary that it set me
thinking, and as it appeared to me that it depended upon the laws of
perspective, I reflected on the manner of constructing it, and was at
length so entirely successful that I made a spy-glass which far
surpasses the report of the Flanders one. As the news had reached
Venice that I had made such an instrument, six days ago I was summoned
before their Highnesses, the Signoria, and exhibited it to them, to
the astonishment of the whole senate. Many of the nobles and senators,
although of a great age, mounted more than once to the top of the
highest church tower in Venice, in order to see sails and shipping
that were so far off that it was two hours before they were seen,
without my spy-glass, steering full sail into the harbor; for the
effect of my instrument is such that it makes an object fifty miles
off appear as large as if it were only five.
“Perceiving of what great utility such an instrument would prove in
naval and military operations, and seeing that His Serenity the Doge
desired to possess it, I resolved on the 24th inst. to go to the
palace and present it as a free gift.” So Galileo did, and as a result
the senate elected him to the Professorship at Padua for life, with a
salary of one thousand florins yearly.
But what were Galileo’s claims to the invention of this great
instrument? Here is what he wrote in 1623. “Perhaps it may be said
that no great credit is due for the making of an instrument, or the
solution of a problem, when one is told beforehand that the instrument
exists, or that the problem is solvable. It may be said that the
certitude of the existence of such a glass aided me, and that without
this knowledge I would never have succeeded. To this I reply, the help
which the information gave me consisted in exciting my thoughts in a
particular direction, and without that, it is possible they may never
have been directed that way; but that such information made the act of
invention easier to me I deny, and I say more--to find the solution of
a definite problem requires a greater effort of genius than to resolve
one not specified; for in the latter case hazard, chance, may play the
greater part, while in the former all is the work of the reasoning and
intelligent mind. Thus, we are certain that the Dutchman, the first
inventor of the telescope, was a simple spectacle-maker, who, handling
by chance different forms of glasses, looked, also by chance, through
two of them, one convex and the other concave, held at different
distances from the eye; saw and noted the unexpected result; and thus
found the instrument. On the other hand, I, on the simple information
of the effect obtained, discovered the same instrument, not by chance,
but by the way of pure reasoning. Here are the steps: the artifice of
the instrument depends either on one glass or on several. It cannot
depend on one, for that must be either convex, or concave, or plain.
The last form neither augments nor diminishes visible objects; the
concave diminishes them, the convex increases them, but both show them
blurred and indistinct. Passing then to the combination of two
glasses, and knowing that glasses with plain surfaces change nothing,
I concluded that the effect could not be produced by combining a plain
glass with a convex or a concave one; I was thus left with the two
other kinds of glasses, and after a few experiments I saw how the
effect sought could be produced. Such was the march of my discovery,
in which I was not assisted in any way by the knowledge that the
conclusion at which I aimed was a verity.”
The telescope that Galileo presented to the Doge of Venice, and which
was later lost, consisted of a tube of lead, with what is called a
plano-concave eye-glass and a plano-convex object glass, and had a
magnifying power of three diameters, which made objects look three
times nearer than they actually were, and as a result nine times
larger. The tube was about seventy centimeters long and about
forty-five millimeters in diameter. It was first used in public from
the top of the campanile in the piazza at Venice on August 21, 1609,
and the most distant object that could be seen through it was the
campanile of the church of San Giustina in Padua, about thirty-five
kilometers away.
As soon as Galileo returned to his home in Padua he busied himself
with improving his invention. First he constructed a new telescope,
which as he said “made objects appear more than sixty times larger.”
Soon he had a still better one, which enlarged four hundred times. He
used this to examine the moon, and said that it brought that body “to
a distance of less than three semi-diameters of the earth, thus making
it appear about twenty times nearer and four hundred times larger than
when seen by the unaided eye.” To use the instrument more accurately
he built a support which held it firmly. He had also now learned to
make the lenses adjustable, by fixing the tubes that held them so that
they could be drawn out of, or pushed into the main tube of the
telescope. To see objects not very far distant very clearly he would
push the glasses a little way apart, and to see things very far
distant he drew the glasses together.
But this last telescope did not altogether satisfy him, and so he
built a still larger one. This brought objects more than thirty times
closer and showed them almost a thousand times larger in size. With
this he discovered the moons of Jupiter, and some of the fixed stars,
and added much to what was already known concerning the Milky Way, a
region of the sky which had long been a puzzle to astronomers.
He spent a great part of his time now in his workshop, making and
grinding glasses. They were expensive and very difficult to prepare
properly. Out of more than one hundred that he ground at first he
found only ten that would show him the newly found moons of Jupiter.
The object glasses were the more difficult, for it was this glass
which had to bring to a focus as accurately as possible all the rays
of light that passed into the telescope.
As the voyage of Columbus had brought a new world in the western ocean
to the notice of Europe, so Galileo’s discoveries with his telescope
brought forth a new world in the skies. Galileo wrote out statements
of his discoveries, and sent these, with his new telescopes, to the
princes and learned men of Italy, France, Flanders, and Germany. At
all the courts and universities the telescopes were received with the
greatest enthusiasm, and put to instant use in the hope of discovering
new stars. But again the followers of Aristotle, those who were
unwilling to admit that anything new could be learned about the laws
of nature or the universe, arose in wrath. They attacked Galileo and
his discoveries. They would not admit that Jupiter had four attendant
moons, although these satellites could be seen by any one through the
telescope, and a little later, when Galileo stated that the planet
Saturn was composed of three stars which touched each other (later
found to be one planet with two rings) they rose up to denounce him.
But as yet these protests against the discoverer had little effect.
Europe was too much interested in what he was showing it to realize
how deeply he might affect men’s views of the universe.
Fame was now safely his. Men came from all parts of Europe to study
under this wonderful professor of Padua. But teaching gave him too
little time to carry on his own researches. So he looked about for
some other position that would give him greater leisure, and finally
stated his wishes to Cosimo II, Duke of Florence. Galileo had named
the satellites of Jupiter after the house of Medici, to which this
Duke belonged, and Cosimo was much flattered at the compliment. As a
result he was soon after made First Mathematician of the University of
Pisa, and also Philosopher and Mathematician to the Grand Duke’s Court
of Florence.
Settled at last at Florence his work as an astronomer steadily went
forward. He discovered that the planet Venus had a varying crescent
form, that there were small spots circling across the face of the sun,
which he called sun-spots, and later that there were mountains on the
moon. He also visited Rome, where he was received with the greatest
good-will by Pope Paul V and his cardinals, and where he met the
leading scientists of the capital.
But Galileo’s course was no less flecked with light and shade than
were the sun and moon he studied. The envy of rivals soon spread false
reports about him, and the professors at Pisa refused to accept the
results of his studies. Then one of the latter stirred the religious
scruples of the Dowager Grand Duchess by telling her that Galileo’s
conclusion that the earth had a double motion must be wrong, since it
was opposed to the statements of the Bible. Galileo heard of this, and
wrote a letter in reply, in which he said that in studying the laws of
nature men must start with what they could prove by experiments
instead of relying wholly on the Scriptures. This was enough to set
the machinery of his enemies in motion. Galileo’s teachings were
pointed out as dangerous to the teachings of the Church, and the
officers of the Inquisition began to consider how they might best deal
with him. Certain of his writings were declared false and prohibited,
and he was admonished that he must follow certain lines in his
teachings. He went to Rome himself, and saw the Pope again, but found
that his friends were fewer and his enemies growing more powerful.
The theory of Copernicus that the earth and planets are in constant
motion was the very foundation of Galileo’s scientific studies, and
yet the order of the Church now forbade him to use this theory. He
went back to Florence out of health and despondent. His old students
were falling away from him through fear of the Pope’s displeasure, and
he was left much alone. But his thirst for knowledge would not let him
rest. He took up his residence in the fine old Torre del Gallo, which
looks down on Florence and the river Arno, and went on with his work.
He wrote out the results of his discoveries, and made a microscope
from a model he had seen. Soon he had greatly improved upon his model,
and had an instrument, which, as he said, “magnifies things as much as
50,000 times, so that one sees a fly as large as a hen.” He sent
copies to some friends, and shortly his microscopes were as much in
demand as his telescopes had been.
In 1632 he published what he called “The Dialogues of Galileo
Galilei.” This divided the world of Italy into two camps, the one
those who believed in Aristotle and the old learning, the other those
who followed Copernicus, Galileo, and Kepler. The Jesuits took up the
gage he had thrown down, and Galileo found the Church of Rome arrayed
against him. The sale of his book was forbidden, a commission was
appointed to bring charges against him, and he was ordered to go to
Rome for trial. The commission reported that Galileo had disobeyed the
Church’s orders by maintaining that the earth moves and that the sun
is stationary, that he had wrongly declared that the movements of the
tides were due to the sun’s stability and the motion of the earth, and
that he had failed to give up his old beliefs in regard to the sun and
the earth as he had been commanded.
Galileo, although he was ill, went to Rome, and was placed on trial
before the Inquisition. After weeks of weary waiting and long
examinations he was ordered to take a solemn oath, forswearing his
belief in his own writings and rejecting the conclusion that the sun
was stationary and that the earth moved. Rather than suffer the pains
of the Inquisition he agreed, and made his solemn declaration.
According to an old story, now discredited, as he rose from his knees
after the ceremony he whispered to a friend “_Eppur si muove_” (It
does move, nevertheless). Whether he said this or not there can be no
doubt but that the great astronomer knew the performance was a farce,
and that the world did move in spite of all the Inquisition could
declare.
The Inquisition did its work ruthlessly. Notices of the sentence
prohibiting the reading of Galileo’s book and ordering all copies of
it to be surrendered, and copies of the declaration he had made
denying his former teachings, were sent to all the courts of Europe
and to many of the universities. In Padua the documents were read to
teachers and students at the university where for so many years
Galileo had been the greatest glory of learning, and in Florence the
Inquisitor read the sentence publicly in the church of Santa Croce,
notices having been sent to all who were known to be friends or
followers of Galileo, ordering them to attend. Thus his humiliation
was spread broadcast, and in addition he was ordered to be held at
Rome as a prisoner.
After a time he was permitted to go on parole to the city of Siena,
which was at least nearer his home outside Florence. There he stayed
until the Grand Duke Cosimo, who had stood by him, persuaded the
Church that Galileo’s health required that he be allowed to join his
friends. At last he reached his home, and again took up his studies.
His eyesight was failing, and eventually he became entirely blind, but
meanwhile his speculations covered the widest fields of science, he
studied the laws of motion and equilibrium, the velocity of light, the
problems of the vacuum, of the flight of projectiles, and the
mathematical theory of the parabola. He wrote another book, dealing
with two new sciences, and was busy with designs for a pendulum clock
at the time of his death in 1642. He was buried in the church of Santa
Croce, the Pantheon of Florence, under the same roof with his great
fellow countryman, Michael Angelo.
What is known as the modern refracting telescope is based upon a
different combination of lenses than that used by Galileo. Kepler
studied Galileo’s instrument, and then designed one consisting of two
convex lenses. The modern telescope follows Kepler’s arrangement, but
Galileo’s adjustment is still suitable where only low magnifying
powers are needed, and is used to-day in the ordinary field- and
opera-glass.
Galileo knew nothing of what we call the reflecting telescope. He
found that by using a convex-lens as an object-glass he could bring
the rays of light from any distant object to a focus, and it did not
apparently occur to him that he could achieve the same end by the use
of a concave mirror. James Gregory, a Scotchman, designed the first
reflector in 1663, and described it in a book, but he was too poor to
construct it. Nine years later Sir Isaac Newton, having studied
Gregory’s plans, built the first reflecting telescope, which is now to
be seen in the hall of the Royal Society in London. But invention has
gone yet farther in perfecting these instruments with which to study
the skies, and the great telescopes of modern times have in most
instances discarded Newton’s reflector for the refracting instrument.
And these are built on a tremendous scale. The Yerkes telescope at
Williams Bay, Wisconsin, has a refractor of forty inches, and the one
built for the Paris Exposition of 1900, one of fifty inches. In
numerous other details they have changed, and yet each is chiefly
indebted to that simple spy-glass of Galileo, by which he was able to
show the nobles and senators of Venice full-rigged ships, which
without it were barely distant specks on the horizon. Or, going still
farther back, the men who make our present telescopes are following
the trail that was first blazed on the day when the Dutch apprentice
of Middleburg chanced to pick up two spectacle lenses and look through
the two of them at once.
Galileo made many great discoveries and inventions; there was hardly a
field of science that he did not enter and explore; but his greatest
work was to open a new world to men’s attention. It was this that
brought him before the Inquisition and that branded him as a dangerous
heretic, and it was this that placed him in the forefront of the
world’s discoverers. Men might say that the earth stood still, because
it suited them best to believe so, but Galileo gave the world an
instrument by which it could study the matter for itself, and the
world has gone on using that instrument and that method ever since.
IV
WATT AND THE STEAM-ENGINE
1736-1819
It was no pressing need that drove John Gutenberg to the invention of
his printing press, nor was it necessity that led to Galileo’s
discovery of the telescope, but it was a very urgent demand that led
to the building of a steam-engine by James Watt. England and Scotland
found that men and women, even with the aid of horses, could not work
the coal mines as they must be worked if the countries were to be kept
supplied with fuel. The small mines were used up, the larger ones must
be deepened, and in that event it would be too long and arduous a task
for men and women to raise the coal in small baskets, or for horses to
draw it out by the windlass. A machine must be constructed that would
do the work more quickly, more easily, and more cheaply.
A Frenchman named Denys Papin had built the first steam-engine with a
piston. He had seen certain experiments that showed him how much
strength there was in compressed air. He had noticed that air pressure
could lift several men off their feet. His problem therefore was how
best to compress the air, or, as it appeared to him, how to secure a
vacuum. His experiments proved that he could do this by the use of
steam. He took a simple cylinder and fitted a piston into it. Water
was put in the cylinder under the piston, a fire was lighted beneath
it, and as the water came to the boiling point the piston was forced
upward by the steam. Then the fire was taken away, and as the steam in
the cylinder condensed, the piston was forced down by the air pressure
above. He fastened the upper end of the piston to a rope, which passed
over two pulleys. If a weight were hung to the other end of the rope
it would be raised as the piston was forced down. In that way the air
pressure did the work of lifting the weight, and the necessary vacuum
was obtained by forming steam and then condensing it in the cylinder.
This was a very primitive device, requiring several minutes for the
engine to make one stroke, but it was the beginning of the practical
use of steam as a motive power.
Thomas Newcomen, an English blacksmith by trade, first put Papin’s
idea to use. Instead of the rope and pulleys Newcomen fastened a
walking-beam to the end of the piston, and attached a pump-rod to the
other end of the walking-beam. He used the steam in the cylinder only
to balance the pressure of the air on the piston, and let the pump-rod
descend by its own weight. As the steam condensed the piston fell, and
the pump-rod rose again. By this means he could pump water from a
mine, or lift coal. His first engine was able to lift fifty gallons of
water fifty yards at each stroke, and could make twelve strokes a
minute. At first he condensed his steam by throwing cold water on the
outside of the cylinder, but one day he discovered that the engine
suddenly increased its speed, and he found that a hole had been worn
in the cylinder, and that the water with which he had covered the top
of the piston was entering through this hole. This condensed the steam
more rapidly, and he adopted it as an improvement in his next engine.
A little later a boy named Humphrey Potter, who had charge of turning
the cocks that let the water and steam into the cylinder, found a way
of tying strings to the cocks so that the engine would turn them
itself, and so originated what came to be known as valve-gear.
Newcomen’s engine was a great help to the coal mines of England and
Scotland, but it was very expensive to run, a large engine consuming
no less than twenty-eight pounds of coal per hour per horse-power.
Then it happened that in 1764 a small Newcomen engine that belonged to
the University of Glasgow was given to James Watt, an instrument-maker
at the university, to be repaired. To do this properly he made a study
of all that had been discovered in regard to engines, and then set
about to construct one for himself.