Produced by Anna Hall, Albert László, Matthew Wheaton and the Online Distributed Proofreading Team at http://www.pgdp.net [Illustration: MARCONI WIRELESS TELEGRAPH STATION, CLIFDEN, IRELAND] Photographed at night while sending a message across the Atlantic. The terrific snapping of the electric discharge is heard by one standing near the station, but no light is seen. The strange light given out from the network of wires is invisible to the eye, but is caught by the photographic plate. [Illustration: THE SAME STATION PHOTOGRAPHED BY DAYLIGHT] THE STORY OF GREAT INVENTIONS BY ELMER ELLSWORTH BURNS INSTRUCTOR IN PHYSICS IN THE JOSEPH MEDILL HIGH SCHOOL, CHICAGO WITH MANY ILLUSTRATIONS HARPER & BROTHERS PUBLISHERS NEW YORK AND LONDON MCMX Copyright, 1910, by HARPER & BROTHERS Published November, 1910. _Printed in the United States of America_ CONTENTS CHAPTER I THE AGE OF ARCHIMEDES Archimedes the first great inventor.--The battle of Syracuse.--Archimedes' principle.--Inventions of the ancient Greeks CHAPTER II THE AGE OF GALILEO Galileo and the battle for truth.--The pendulum clock.--Galileo's experiment with falling shot.--The telescope.--Galileo's struggle.--Torricelli and the barometer.--Otto von Guericke and the air-pump.--Robert Boyle and the pressure of air and steam.--Pascal and the hydraulic press.--Newton.--Gravitation.--Colors in sunlight CHAPTER III THE EIGHTEENTH CENTURY James Watt and the steam-engine.--The first steam-engine with a piston.--Newcomen's engine.--Watt's engine.--Horse-power of an engine.--The Leyden jar.--Conductors and insulators.--Two kinds of electric charge.--Franklin's kite experiment.--The lightning-rod.--Galvani and the electric current.--Volta and the electric battery CHAPTER IV FARADAY AND THE FIRST DYNAMO Count Rumford.--Count Rumford's experiment with the cannon.--Davy.--Faraday's electrical discoveries.--Oersted and electromagnetism.--Ampère.--Arago.--Faraday's first electric motor.--An electric current produced by a magnet.--Detecting and measuring an electric current.--An electric current produced by the magnetic field of another current.--Faraday's dynamo.--A wonderful law of nature CHAPTER V GREAT INVENTIONS OF THE NINETEENTH CENTURY Electric batteries.--The dry battery.--The storage battery.--The dynamo.--Siemens' dynamo.--The drum armature.--Edison's compound-wound dynamo.--Electric power.--The first electric railway.--Electric lighting.--The telegraph.--Duplex telegraphy.--The telephone.--The phonograph.--Gas-engines.--The steam locomotive.--How a locomotive works.--The turbine CHAPTER VI THE TWENTIETH-CENTURY OUTLOOK Air-ships.--The aeroplane.--How the Wright aeroplane is kept afloat.--Submarines.--Some spinning tops that are useful.--The monorail-car.--Liquid air and the greatest cold.--The electric furnace and the greatest heat.--The wireless telegraph.--The wireless telephone.--Wonders of the alternating current.--X-rays and radium APPENDIX Brief notes on important inventions INDEX ILLUSTRATIONS FIG. MARCONI WIRELESS-TELEGRAPH STATION, CLIFDEN, IRELAND THE SAME STATION PHOTOGRAPHED BY DAYLIGHT 1--THE BATTLE OF SYRACUSE 2--GALILEO'S PENDULUM CLOCK 3--AN AIR THERMOMETER 4--TORRICELLI'S EXPERIMENT 5--GUERICKE'S AIR-PUMP 6--GUERICKE'S WATER BAROMETER 7--A LIFT-PUMP 8--A SIMPLE HYDRAULIC PRESS 9--HOW AN HYDRAULIC PRESS WORKS 10--AN HYDRAULIC PRESS WITH BELT-DRIVEN PUMP 11--NEWTON'S EXPERIMENT WITH THE PRISM 12--PAPIN'S ENGINE 13--THE NEWCOMEN ENGINE, IN REPAIRING WHICH WATT WAS LED TO HIS GREAT DISCOVERIES 14--CYLINDER OF WATT'S STEAM-ENGINE 15--A FLY-BALL GOVERNOR 16--A LEYDEN JAR 17--FRANKLIN'S KITE EXPERIMENT 18--VOLTA EXPLAINING HIS ELECTRIC BATTERY TO NAPOLEON BONAPARTE 19--THE FIRST ELECTRIC BATTERY 20--COUNT RUMFORD'S EXPERIMENT WITH THE CANNON, MAKING WATER BOIL WITHOUT FIRE 21--OERSTED'S EXPERIMENT 22--A COIL WITH A CURRENT FLOWING THROUGH IT ACTS LIKE A MAGNET 23--A BAR OF SOFT IRON WITH A CURRENT FLOWING AROUND IT BECOMES A MAGNET 24--TWO COILS WITH CURRENTS FLOWING IN THE SAME DIRECTION ATTRACT EACH OTHER 25--TWO COILS WITH CURRENTS FLOWING IN OPPOSITE DIRECTIONS REPEL EACH OTHER 26--ARAGO'S EXPERIMENT 27--ONE POLE OF A MAGNET SPINS ROUND A WIRE THROUGH WHICH AN ELECTRIC CURRENT FLOWS 28--WHEN A MAGNET IS THRUST INTO A COIL OF WIRE IT CAUSES A CURRENT TO FLOW IN THE COIL, BUT THE CURRENT FLOWS ONLY WHILE THE MAGNET IS MOVING 29--A COIL OF WIRE AROUND A COMPASS-NEEDLE 30--FARADAY'S INDUCTION-COIL 31--HISTORICAL APPARATUS OF FARADAY IN THE ROYAL INSTITUTION 32--FARADAY'S FIRST DYNAMO 33--FARADAY'S LABORATORY, WHERE THE FIRST DYNAMO WAS MADE 34--THE FIRST TRANSFORMER 35--THE "MAGNETIC FIELD" IS THE SPACE AROUND A MAGNET IN WHICH IT WILL ATTRACT IRON 36--MAGNETIC FIELD OF A HORSESHOE MAGNET 37--A DANIELL CELL 38--A GRAVITY CELL 39--SHOWING WHAT IS IN A DRY BATTERY 40--A STORAGE BATTERY, SHOWING THE "GRIDS" 41--A STORAGE-BATTERY PLATE MADE FROM A SHEET OF LEAD 42--STURGEON'S ELECTROMAGNET 43--AN ELECTROMAGNET WITH MANY TURNS OF INSULATED WIRE 44--AN ELECTROMAGNET LIFTING TWELVE TONS OF IRON 45--A DYNAMO WITH SIEMENS' ARMATURE 46--RING ARMATURE 47--FIRST DYNAMO PATENTED IN THE UNITED STATES 48--A DRUM ARMATURE, SHOWING HOW AN ARMATURE OF FOUR COILS IS WOUND 49--A SERIES-WOUND DYNAMO 50--A SHUNT-WOUND DYNAMO 51--A COMPOUND-WOUND DYNAMO 52--ONE OF EDISON'S FIRST DYNAMOS 53--A DYNAMO MOUNTED ON THE TRUCK OF A RAILWAY CAR 54--FIRST ELECTRIC LOCOMOTIVE 55--FIRST EDISON ELECTRIC LOCOMOTIVE 56--EDISON'S FIRST PASSENGER LOCOMOTIVE 57--FIRST COMMERCIAL ELECTRIC RAILWAY 58--EDISON, AMERICA'S GREATEST INVENTOR, AT WORK IN HIS LABORATORY 59--EDISON'S FAMOUS HORSESHOE PAPER-FILAMENT LAMP OF 60--FIRST COMMERCIAL EDISON ELECTRIC-LIGHTING PLANT; INSTALLED ON THE STEAMSHIP "COLUMBIA" IN MAY, 61--A TELEGRAPH SOUNDER 62--MORSE'S FIRST TELEGRAPH INSTRUMENT 63--A TELEGRAPHIC CIRCUIT WITH RELAY AND SOUNDER 64--A SIMPLE TELEGRAPHIC CIRCUIT 65--FIRST TELEGRAPH INSTRUMENT USED FOR COMMERCIAL WORK 66--HOW TWO MESSAGES ARE SENT OVER ONE WIRE AT THE SAME TIME 67--HOW TWO MESSAGES ARE SENT OVER ONE WIRE AT THE SAME TIME. BRIDGE METHOD 68--FIRST BELL TELEPHONE RECEIVER AND TRANSMITTER 69--A TELEPHONE RECEIVER 70--TWO RECEIVERS USED AS A COMPLETE TELEPHONE 71--CARBON-DUST TRANSMITTER 72--THE PHONAUTOGRAPH, A FORERUNNER OF THE PHONOGRAPH 73--EDISON'S FIRST PHONOGRAPH AND A MODERN INSTRUMENT 74 to--THE FOUR-CYCLE GAS-ENGINE 78--TWO-CYCLE GAS-ENGINE. CRANK AND CONNECTING-ROD ARE ENCLOSED WITH THE PISTON 79--SELDEN "EXPLOSION BUGGY," FORERUNNER OF THE MODERN AUTOMOBILE 80--SOME EARLY LOCOMOTIVES 81--HOW A LOCOMOTIVE WORKS 82--HERO'S ENGINE 83--AN UNDERSHOT WATER-WHEEL WITH CURVED BLADES 84--AN OVERSHOT WATER-WHEEL 85--DE LAVAL STEAM-TURBINE 86--A MODERN STEAM-TURBINE WITH TOP CASING RAISED SHOWING BLADES 87--DIAGRAM OF TURBINE SHOWN IN FIG. 88--A STEAM-TURBINE THAT RUNS A DYNAMO GENERATING 14,000 ELECTRICAL HORSE-POWER 89--BRITISH ARMY AIR-SHIP "NULLI SECUNDUS" READY FOR FLIGHT 90--BASKET, MOTOR, AND PROPELLER OF THE BRITISH ARMY AIR-SHIP "NULLI SECUNDUS" 91--A ZEPPELIN AIR-SHIP 92--COUNT ZEPPELIN'S "DEUTSCHLAND," THE FIRST AIR-SHIP IN REGULAR PASSENGER SERVICE 93--THE BALDWIN AIR-SHIP USED IN THE UNITED STATES ARMY 94--IN FULL FLIGHT 95--WRIGHT AIR-SHIP IN FLIGHT 96--HOW THE WRIGHT AIR-SHIP IS KEPT AFLOAT 97--THE SEAT AND MOTOR OF THE WRIGHT AEROPLANE 98--THE BLÉRIOT MONOPLANE 99--THE "PLUNGER" 100--U. S. SUBMARINE "SHARK" READY FOR A DIVE 101--FIRST SUBMARINE CONSTRUCTED IN THE UNITED STATES. IT WENT TO THE BOTTOM WITH SEVEN MEN, WHO WERE DROWNED 102--HOW MEN IN A SUBMARINE SEE WHEN UNDER THE WATER 103--A TOP THAT SPINS ON A STRING 104--A CAR THAT RUNS ON ONE RAIL 105--MANUFACTURING DIAMONDS--FIRST OPERATION 106--MANUFACTURING DIAMONDS--SECOND OPERATION 107--MANUFACTURING DIAMONDS--THIRD OPERATION 108--MARCONI AND HIS WIRELESS-TELEGRAPH SENDING AND RECEIVING INSTRUMENTS 109--DIAGRAM OF WIRELESS-TELEGRAPH SENDING APPARATUS 110--DIAGRAM OF MARCONI WIRELESS-TELEGRAPH RECEIVING APPARATUS 111--RECEIVER OF BELL'S PHOTOPHONE 112--A GAS FLAME IS SENSITIVE TO ELECTRIC WAVES 113--CAPTAIN INGERSOLL ON BOARD THE U. S. BATTLE-SHIP "CONNECTICUT" USING THE WIRELESS TELEPHONE 114--INCANDESCENT ELECTRIC LAMP LIGHTED THOUGH NOT CONNECTED TO ANY BATTERY OR DYNAMO 115--AN ELECTRIC DISCHARGE AT A PRESSURE OF 12,000,000 VOLTS, A CURRENT OF 800 AMPERES IN THE SECONDARY COIL 116--AN ELECTRIC DISCHARGE SIXTY-FIVE FEET IN LENGTH 117--A PHYSICIAN EXAMINING THE BONES OF THE ARM BY MEANS OF X-RAYS 118--X-RAY PHOTOGRAPH OF THE EYE 119--PHOTOGRAPH MADE WITH RADIUM INTRODUCTORY NOTE Great inventions are a never-failing source of interest to all of us, and particularly to the boy in his teens. The dynamo, the electric motor, the telegraph, with and without wires, the telephone, air-ships, and many other inventions excite in him an interest which is deeper than mere curiosity. He wants to know how these things work, and how they were invented. The man is so absorbed in the present that he cares little for the past. Not so with the boy. He cares for the history of inventions, and in this he is wiser than the man, for it is only by a study of its origin and growth that we can understand the larger significance of a great invention. Great inventions have their origin in great discoveries. The story of great inventions, therefore, includes the story of the discoveries out of which they have arisen. The stories of the discoveries and the inventions are inseparable from the lives of the men who made them, and so we must deal with biography, which in itself is of interest to the boy. Such a story is the story of physical science in the service of humanity. The interest of the youth in great inventions is unquestioned. Shall we stifle this interest by overemphasis of technical detail, or shall we minister to it as a thing vital in the life of the youth of to-day? A few sentences quoted from G. Stanley Hall will indicate the author's point of view. "The youth is in the humanist stage. Nature is sentiment before it becomes idea or formula or utility." "The heroes and history epochs of each branch [of science] add another needed quality to the still so largely humanistic stage." "A new discovery, besides its technical record, involves the added duty of concise and lucid popular statement as a tribute to youth." The need of a "concise and lucid popular statement" of the rise of the great inventions which form the material basis of our modern civilization and all of which are new to the young mind, has no doubt been keenly felt by others as it has been by the author. The story of our great inventions has been told in sundry volumes for adult readers, but nowhere has this story, alive with human interest, been told in a form suited to the young. It was the realization of this need growing out of years of experience in teaching these branches that led the author to attempt the task of writing the story. The purpose of this book is to tell in simple language how our great inventions came into being, to depict the life-struggles of the men who made them, and, in the telling of the story, to explain the working of the inventions in a way the boy can understand. The stories which are here woven together present the great epochs in the history of physics, and are intended to give to the young reader a connected view of the way in which our great inventions have arisen out of scientific discovery on the one hand, and conditions which we may call social and economic on the other hand. If the book shall appeal to young readers, and lead them to an appreciation of the meaning of a great invention, the author will feel that his purpose has been achieved. The author is deeply indebted to Dr. Charles A. McMurry and Prof. Newell D. Gilbert, of the Northern Illinois State Normal School; Profs. C. R. Mann and R. A. Millikan, of the University of Chicago; and Prof. John F. Woodhull, of Columbia University, for reading the manuscript and offering valuable suggestions. Acknowledgment is further made here of valuable aid in collecting material for illustrations and letter-press. Such acknowledgment is due to Prof. A. Gray, University of Glasgow; Prof. Antonio Favaro, Royal University of Padua; Prof. A. Zammarchi, Brescia, Italy; Mr. Nikola Tesla; the Royal Institution, London; _McClure's Magazine_; _The Technical World Magazine_; _The Scientific American_; the Ellsworth Company; Commonwealth-Edison Company; Association of Edison Illuminating Companies; Electric Controller and Supply Company; Kelley-Koett Manufacturing Company; Watson-Stillman Company; Gould Storage Battery Company; Thordarson Electric Company; the Westinghouse Machine Company; Marconi Wireless Telegraph Company of America, and the Siemens-Schuckert Werke, Berlin. The drawings illustrating Faraday's experiments are from exact reproductions of Faraday's apparatus, made by Mr. Joseph G. Branch, author of _Conversations on Electricity_, and are reproduced by his kind permission. E. E. B. CHICAGO, _June, 1910_. THE STORY OF GREAT INVENTIONS Chapter I THE AGE OF ARCHIMEDES Archimedes, the First Great Inventor Archimedes, the first great inventor, lived in Syracuse more than two thousand years ago. Syracuse was a Greek city on the island of Sicily. The King of Syracuse, Hiero, took great interest in the discoveries of Archimedes. One day Archimedes said to King Hiero that with his own strength he could move any weight whatever. He even said that, if there were another earth to which he could go, he could move this earth wherever he pleased. The King, full of wonder, begged of him to prove the truth of his statement by moving some very heavy weight. Whereupon Archimedes caused one of the King's galleys to be drawn ashore. This required many hands and much labor. Having manned the ship and put on board her usual loading, he placed himself at a distance and easily moved with his hand the end of a machine which consisted of a variety of ropes and pulleys, drawing the ship over the sand in as smooth and gentle a manner as if she had been under sail. The King, quite astonished, prevailed with Archimedes to make for him all manner of machines which could be used either for attack or defence in a siege. The Battle of Syracuse During the life of King Hiero Syracuse had no occasion to use the war machines of Archimedes. The grandson of King Hiero, who succeeded to the throne, was a tyrant. He attempted to throw off the sovereignty of Rome and entered into an alliance with Carthage. His cruelty toward his own people was so great that, after a short reign, he was assassinated. There was anarchy in Syracuse for a time, the Roman and anti-Roman parties striving for supremacy. The anti-Roman party gaining possession of the city, the Romans, in order to bring Syracuse again into subjection, prepared for an attack by sea and land. Then it was that Syracuse had need of the war machines made by Archimedes (Fig. 1). [Illustration: FIG. 1--THE BATTLE OF SYRACUSE The city defended by the inventions of Archimedes.] The Romans came with a large land force and a fleet. They were sure that within five days they could conquer the city. But there are times when one man with brains is worth more than an army. In the battle which followed, Archimedes with his inventions was more than a match for the Romans. The city was strong from the fact that the wall on one side lay along a chain of hills with overhanging brows; on the other side the wall had its foundation close down by the sea. A fleet of sixty ships commanded by Marcellus bore down upon the city. The ships were full of men armed with bows and slings and javelins with which to dislodge the men who fought on the battlements. Eight ships had been fastened together in pairs. These double vessels were rowed by the outer oars of each of the pair. On each pair of ships was a ladder four feet wide and of a height to reach to the top of the wall. Each side of the ladder was protected by a railing, and a small roof-like covering, called a penthouse, was fastened to the upper end of the ladder. This covering served to protect the soldiers until they could reach the top of the wall. They thought to bring these double ships close to shore, raise the ladders by ropes and pulleys until they rested against the wall, then scale the wall and capture the city. But Archimedes had crossbows ready, and, when the ships were still at some distance, he shot stones and darts at the enemy, wounding and greatly annoying them. When these began to carry over their heads, he used smaller crossbows of shorter range, so that stones and darts fell constantly in their midst. By this means he checked their advance, and finally Marcellus, in despair, was obliged to bring up his ships under cover of night. But when they had come close to land, and so too near to be hit by the crossbows, they found that Archimedes had another contrivance ready. He had pierced the wall as high as a man's head with many loopholes which on the outside were about as big as the palm of the hand. Inside the wall he had stationed archers and men with crossbows to shoot down the marines. By these means he not only baffled the enemy, but killed the greater number of them. When they tried to use their ladders, they discovered that he had cranes ready all along the walls, not visible at other times but which suddenly reared themselves above the wall from the inside and stretched their beams far over the battlements, some of them carrying stones weighing about five hundred pounds, and others great masses of lead. So, whenever the ships came near, these beams swung round on their pivots and by means of a rope running through a pulley dropped the stones upon the ships. The result was that they not only smashed the ships to pieces, but killed many of the soldiers on board. Another machine made by Archimedes was an "iron hand" or grappling-hook swung on a chain and carried by a crane. The hook was dropped on the prow of a ship, and when it had taken hold the ship was lifted until it stood on its stern, then quickly dropped, causing it either to sink or ship a great quantity of water. With such machines, unknown before, Archimedes drove back the enemy. On the landward side similar machines were used. The Romans were reduced to such a state of terror that "if they saw but a rope or a stick put over the walls they cried out that Archimedes was levelling some machine at them and turned their backs and fled." After a long siege, however, hunger forced the Syracusans to surrender. Marcellus so admired the genius of Archimedes that he gave orders that he should not be injured. Yet, in the sack of the city which followed, Archimedes was slain by a Roman soldier. The Roman historian Livy records that "Archimedes, while intent on some figures which he had made in the dust, although the confusion was as great as could possibly be, was put to death by a soldier who did not know who he was; that Marcellus was greatly grieved at this, and that pains were taken about his funeral, while his relations also were carefully sought and received honor and protection on account of his name and memory." Archimedes' Principle Hiero, when he became King of Syracuse, decreed that a crown of gold, of great value, should be placed in a certain temple as an offering to the gods, and sent to a manufacturer the correct weight of gold. In due time the crown was brought to the King, and a beautiful piece of work it was. The weight of the crown was the same as that of the gold, but a report was circulated that some of the gold had been taken out and silver supplied in its place. Hiero was angry, but knew no method by which the theft might be detected. He therefore requested Archimedes to give the matter his attention. While trying to solve this problem Archimedes went one day to a bath. As he got into the bath-tub he saw that as his body became immersed the water ran out of the tub. He quickly saw how he could solve the problem, leaped out of the bath in joy, and, running home naked, cried out with a loud voice "Eureka! eureka!" (I have found it! I have found it!) Using a piece of gold and a piece of silver, each equal in weight to the crown, and a large vase full of water, he proved that the crown was not pure gold, and found how much silver had been mixed with the gold. The incident of the golden crown may have been the starting-point of Archimedes' study of solid bodies when immersed in fluids. Every one knows that a boy can lift a heavy stone under water that he could not lift out of water. The stone seems lighter when in the water. A diver with his lead-soled shoes could scarcely walk on land, but walks easily under water. When the diver comes up, the place where he was immediately becomes filled with water. Now, whatever that water weighs which fills the diver's place, just that much weight will the diver lose when he goes down. What is true of the diver is true of the stone or of any object under water. The stone when in the water loses just as much weight as the weight of the water that would fill its place. This is the fact which was discovered by Archimedes and which is called "Archimedes' Principle." It is said by an ancient author that Archimedes invented more than forty machines. Of these the best known are the block and tackle, the endless screw (worm gear), and the water snail, or Archimedean screw. Yet his delight was not in his machines, but in his mathematics. Though he had invented machines to please his king, he regarded such work as trifling, and took little interest in the common needs of life. Inventions of the Ancient Greeks The common needs of life are to-day the chief concern of the greatest men, and so we find it hard to sympathize with this view of Archimedes. His view, however, was that of other learned men of his time, that the common needs of life are beneath the dignity of the scholar, and so we can see why the Greeks made so few great inventions. Hero, who lived a century later than Archimedes, invented a steam-engine, which, however, was only a toy. A water-clock, in which the first cog-wheels were used, was invented by another Greek named Ktesibus, who also invented the force-pump. The suction-pump was known in the time of Aristotle, who lived about a century before the time of Archimedes, but the inventor is unknown. Concerning electricity, the Greeks knew very little. They knew that amber when rubbed will attract light objects, such as dust or chaff. Amber was called by the Greeks "electron," because it reflected the brightness of the sunlight, and their name for the sun was "Elector." From the Greek name for amber we get our word "electricity." The Greeks possessed scarcely more knowledge of magnets than of electricity. In fact, their ideas of magnets cannot be called knowledge, for they consisted chiefly of legends. They told of the shepherd Magnes, who, while watching his flock on Mount Ida, suddenly found the iron ferrule of his staff and the nails of his shoes adhering to a stone; that, later, this stone was called, after him, the "Magnes stone," or "Magnet." They told impossible stories of iron statues being suspended in the air by means of magnets, and of ships sailing near the magnetic mountains when every nail and piece of iron in the ship would fly to the mountain, leaving the ship a wreck upon the waves. Chapter II THE AGE OF GALILEO Galileo and the Battle for Truth For eighteen centuries after the time of Archimedes no inventions of importance were made. Men sought for truth where truth could not be found. They looked within their mouldy manuscripts and asked, "What do the great philosophers say ought to happen?" instead of looking at nature and asking, "What does happen?" And when a man arose who dared to doubt the authority of the old masters and turn to nature to find out the truth, all the weapons at the command of the old school were hurled against him. Let us, at this distance, blame neither the one side nor the other. The conflict was inevitable. It was an accident of history that the brunt of the attack fell upon a man born in Italy in 1564, and that the battle was fought chiefly in the "Eternal City," from which centuries before had marched the legions that conquered the world. The boy, Galileo, who was to become the central figure of the great conflict, was talented in many ways. In lute-playing his skill excelled that of his father, who was one of the noted musicians of his day. His skill in drawing was such that noted artists submitted their work to him for criticism. He wrote essays on the works of Dante and other classical writers. He amused his boy companions by constructing toy machines which, though ingenious, did not always work. His preference was for mechanics, but, as this subject offered little prospect of profitable work, he took up the study of medicine in accordance with his father's wishes. In his eighteenth year he entered the University of Pisa. Here he found men who refused to think for themselves, but decided every question by referring to what the ancient philosophers said. Galileo could not endure such slavish submission to authority. So strongly did he assert himself that he was nicknamed "The Wrangler," and, by his wrangling, he lost a scholarship in the university. He neglected his medical studies and secretly studied mathematics. His father, learning of this, consented to his becoming a mathematician. Thus he followed his bent, though it seemed to lead directly to poverty. The Pendulum Clock It was while a student at the University of Pisa that he discovered a law of pendulums which makes possible our pendulum clocks. While at his devotions in the cathedral, he observed the swinging of the bronze lamp which had been drawn back for lighting. Timing its swinging by means of his pulse, the only timepiece in his possession, he found that the time of one swing remained the same, though the length of the swing grew smaller and smaller. This discovery led to his invention of an instrument for physicians' use in timing the pulse. About fifty years later he invented the pendulum clock (Fig. 2). [Illustration: FIG. 2--GALILEO'S PENDULUM CLOCK It had only one hand, which is not shown in the picture.] Lack of funds compelled him to leave the university without completing his course. He returned to the parental roof and continued his scientific studies. The writings of Archimedes were his favorite study. With Archimedes' famous experiment on King Hiero's crown as a starting-point, he discovered the laws of floating bodies, which explain why a ship or other object floats on water, and invented a balance for weighing objects in water. But such employment won nothing more substantial than honor and fame. Food and clothing were needed. For two years he strove without success to secure employment. At the end of that time he was appointed professor of mathematics in the University of Pisa at the magnificent salary of sixty scudi (about sixty-three dollars) per year. "But any port in a storm; and in Galileo's needy circumstances even this wretched salary was not to be rejected." Moreover, he could add somewhat to his income by private tutoring. Galileo's Experiment with Falling Shot While teaching at the University of Pisa, he performed his famous experiment of dropping from the top of the leaning tower two shot, one weighing ten pounds, the other one pound. Now, according to Aristotle, the ten-pound shot should fall in one-tenth the time required by the one-pound shot. But the assembled company of professors and students saw the two shot start together, fall together, and strike the ground at the same instant, and still refused to believe their own eyes. They continued to affirm that a weight of ten pounds would reach the ground in a tenth of the time taken by a one-pound weight, because they were able to quote chapter and verse in which Aristotle assured them that such is the fact. Thus Galileo made enemies of the other professors, but for a time they could do nothing more than annoy him. About this time Galileo incurred the wrath of the Grand Duke of Tuscany, from whom he had received his appointment. He was commissioned to examine a machine invented by a nephew of the Grand Duke for the purpose of cleaning harbors. Galileo plainly said that the machine was worthless. It was tried, and his opinion proved true. But like the kings of olden time who killed the bearer of evil tidings even though the tidings were true, his enemies made his position so unpleasant that he resigned. He had neither employment nor money. His father's death occurring about this time, threw upon him the care of a mother, a worthless brother, and two sisters. In his distress he sought help from a friend, and secured an appointment as professor of mathematics in the University of Padua. His salary was one hundred and eighty florins (about ninety-five dollars), while other professors received more than ten times as much. While at Padua, Galileo was busy inventing. He invented the sector, which is to be found in most cases of mathematical instruments and is used in certain kinds of drawing. He also invented an air thermometer (Fig. 3), the first instrument for measuring temperature. [Illustration: FIG. 3--AN AIR THERMOMETER When the air in the bulb grows cooler it contracts, and the air outside forces the Water up the tube. When the air in the bulb grows warmer it expands and forces the water down in the tube.] In 1604 there appeared a new star of great brilliancy. It continued to shine with varying brightness for eighteen months, and then vanished. This was a strange event, and Galileo made use of it. He proved that the new star must lie among the most distant of the heavenly bodies, and this fact did not agree with Aristotle's view that the heavens are perfect, and therefore never change. A heated controversy followed, and Galileo came out boldly in favor of the theory that the earth revolves about the sun, the prevailing notion then being that the earth does not move, but that the sun and other heavenly bodies revolve around it. The Telescope In 1609 Galileo learned of a discovery that was to be of great value to the world, but a source of untold trouble to himself. An apprentice of a Dutch optician, while playing with spectacle lenses, chanced to observe that if two of the lenses were placed in a certain position objects seen through them appeared much nearer. Galileo, learning of this, set to work to construct a spy-glass, applying his knowledge of light. In one day he had constructed such an instrument, in which he used two lenses like the lenses of the modern opera-glass. Thus, while the Dutchman's discovery was by accident, Galileo's was by reasoning, and was the more fruitful, as we shall see. Galileo continued improving his telescope until he had made one which would magnify thirty times. He was the first to apply the telescope to the study of the heavenly bodies. The most startling of his discoveries was that of the moons of the planet Jupiter, which he called new planets. This aroused the fury of his enemies, who ridiculed the idea of there being new planets; "for," they said, "to see these planets they must first be put inside the telescope." The excitement was intense. Poets chanted the praise of Galileo. A public fête was held in his honor. One of his pupils was imprisoned in the tower of San Marco, where he had gone to make observations with his telescope, and could not escape until the crowd had satisfied their curiosity. Some of the philosophers refused to look lest they should see and be convinced. Galileo's Struggle His enemies sought to steal from him the honor of his discoveries. Some claimed to have made the discoveries before Galileo did. Others claimed that his discoveries were false, that their only use was to gratify Galileo's vanity and thirst for gold. In these trying times the friendship of the great astronomer Kepler warded off some of the most exasperating attacks. Galileo's fame spread throughout Europe. Students came in great numbers, so that he had little leisure left for his own studies. He therefore decided to leave Padua, and secured an appointment as mathematician and philosopher to the Grand Duke of Tuscany. This appointment took him to Florence. It was here that an incident occurred that marked the beginning of a persecution which continued to the end of his life. As we read the story of this conflict let us remember that it was not primarily a conflict between the Roman Catholic Church and Galileo. It was a conflict of principles. On the one side were arrayed those who said that men should always believe as the ancient writers did; on the other, those who said men should think for themselves. In the first party were most of the university professors and others who dreaded the introduction of new beliefs, whether in religion or science. In the second party were Galileo and a small band of devoted followers. At a dinner at the table of the Grand Duke in Pisa the conversation turned on the moons of Jupiter. Some praised Galileo. Others condemned him, saying that the Holy Scriptures were opposed to his theory of the motion of the earth. A friend reported the incident to Galileo, and he replied to the arguments of his opponents in a letter which was made public. No doubt the sting of his sarcasm made his enemies more bitter. He admitted that the Scriptures cannot lie or err, but this, he said, does not hold good of those who attempt to explain the Scriptures. In another letter, he quoted with approval a saying of Cardinal Baronius, "The Holy Spirit intended to teach us in the Bible how to go to Heaven, not how the heavens go." The first shot had been fired. The battle was on, and the Church, because it possessed the most powerful weapons of attack, was used by the combined forces to break the power of Galileo's reasoning. He went to Rome to make his defence, but was commanded by the Holy Office not to hold or teach that the sun is immovable, and that the earth moves about the sun. During another visit to Rome there was shown to Galileo an instrument which, it was said, would show a flea as large as a cricket. Galileo recalled that some years before he had so arranged a telescope that he had seen flies which he said looked as big as a lamb, and were covered all over with hair. This was the first microscope. Galileo quickly improved the instrument, and soon his microscopes were in great demand. In violation of the decree of the Church, to which he had submitted, he published his most famous work in which he defended the theory that the earth moves about the sun. The book was the outcome of his life-work, but the Church believed it dangerous. He was summoned to Rome. Confined to a sick-bed, he pleaded for delay, which was granted. Before he recovered, however, the summons was made imperative. He must go to Rome, or be carried in irons. He went in a litter, carried by servants of the Grand Duke. In Rome he was to appear before the Inquisition. There he was treated with a consideration never before accorded to a prisoner of the Inquisition. Nor was he subjected to torture, as has been stated by some. He was found guilty of teaching the doctrine that the sun does not move, and that the earth moves about the sun. He was compelled to recant, and sentenced to the prison of the Holy Office and, by way of penance, to repeat once a week for three years the seven penitential Psalms. He yielded without reserve to the decree of the Inquisition, renounced his "errors and heresies," and, with his hand on the Bible, took oath never again to teach the forbidden doctrine. And now, though a shattered old man of seventy-four, enjoined to silence on the chief results of his life-work, nothing could quench his devotion to science. In these last years, he published a new book which, with his earlier work, entitles him to be regarded as the founder of the science of mechanics. In his study of machines Galileo found that no machine will do work of itself. Whenever a machine is at work, a man or a horse, or some other power, is at work upon the machine. In no case will a machine do work without receiving an equal amount of work. Torricelli and the Barometer Galileo had a pump which he found would not work when the water was thirty-five feet below the valve. He thought the pump was injured, and sent for the maker. The maker assured him that no pump would do better. This led Torricelli, one of Galileo's pupils, to the discovery of the barometer. Men had said that water rises in a pump because nature abhors a vacuum. Torricelli believed that air-pressure and not nature's "horror of a vacuum" is the cause of water rising in a pump. He invented the barometer to measure air-pressure. The first barometer was a glass tube filled with quick-silver or mercury (Fig. 4). The tube was closed at the upper end, and the lower end, which was open, dipped in a dish of mercury. He allowed the tube to stand, and saw that the height of the mercury changed. This he believed was because the air-pressure changed. Wind, Torricelli said, is caused by a difference of air-pressure, which is due to unequal heating of the air. For this reason a cool breeze blows from the mountain top to the heated valley, or from sea to land on a summer day. [Illustration: FIG. 4--TORRICELLI'S EXPERIMENT] Otto Von Guericke and the Air-Pump About this time a German burgomaster, Otto von Guericke, of Magdeburg, was performing experiments on air-pressure. The Thirty Years' War had been raging for thirteen years. The Swedish King, Gustavus Adolphus, had landed in Germany, and was winning victory after victory over the imperial troops. Magdeburg had entered into an alliance with the Swedish King, by which he was granted free passage through the city, while, on the other hand, he promised protection to the city. The imperial army under Tilly and Pappenheim laid siege to the city. On the one side there was hope that Gustavus would arrive in time to effect a rescue; on the other, a determination to conquer before such aid could arrive. While Gustavus was on his way to the rescue, Magdeburg was taken by storm, and the most horrible scene of the Thirty Years' War was enacted. Tilly gave up the city to plunder, and his soldiers without mercy killed men, women, and children. In the midst of the scene of carnage the city was set on fire, and soon the horrors of fire were added to the horrors of the sword. In less than twelve hours twenty thousand people perished. Guericke's house and family were saved, but the sufferings of the city were not yet ended. In five years the enemy was again before the walls, and Magdeburg, then in the possession of the Swedes, was compelled to yield to the combined Saxon and imperial troops. Guericke entered the service of Saxony, and was again made mayor of the city. In the midst of these scenes of war, he found time to continue his studies. He made the first air-pump, and with it performed experiments which led to some very important results. The experiments which Guericke made with his air-pump aroused the attention of the princes, and especially Emperor Ferdinand. Guericke was called to perform his experiments before the Emperor. The most striking of these experiments he performed with two hollow copper hemispheres about a foot in diameter, fitted closely together. When the air was pumped out, sixteen horses were barely able to pull the hemispheres apart, though, when air was admitted, they fell apart of their own weight. Another experiment which astonished his audience was performed with the cylinder of a large pump (Fig. 5). A rope was tied to the piston. This rope was passed over a pulley, and a large number of men applied their strength to the rope to hold the piston in place. When the air was taken out of the cylinder, the piston was forced down by air-pressure, and the men were lifted violently from the ground. This experiment, as we shall see, was of great importance in the invention of the steam-engine. [Illustration: FIG. 5--GUERICKE'S AIR-PUMP Men lifted from the ground by air-pressure.] Guericke's study of air-pressure led him to make a water barometer (Fig. 6). This consisted of a glass tube about thirty feet long dipping into a dish of water. The tube was filled with water, and the top projected above the roof of the house. On the water in the tube he placed a wooden image of a man. In fair weather the image would be seen above the housetop. On the approach of a storm the image would drop out of sight. This led his superstitious neighbors to accuse him of being in league with Satan. [Illustration: FIG. 6--GUERICKE'S WATER BAROMETER In fair weather the image appeared above the housetop. When a storm was approaching the image dropped below the roof into the house.] The first electrical machine was made by Guericke. This was simply a globe of sulphur turning on a wooden axle. He observed that when the dry hand was held against the revolving globe, the globe would attract bits of paper and other light objects. Robert Boyle and the Pressure of Air and Steam Robert Boyle, in England, improved the air-pump and performed many new and interesting experiments with it. One of his experiments was to make water boil by means of an air-pump without applying heat. It is now well known that water when boiling on a high mountain is not so hot as when boiling down in the valley. This is because the air-pressure is less on the mountain top than in the valley. By using an air-pump to remove the air-pressure, water may be made to boil when it is still quite cold to the hand. Boyle compared the action of air under pressure to a steel spring. The "spring" of the air is evident to us in the pneumatic tire of the bicycle or automobile. Boyle found that the more air is compressed the greater is its pressure or "spring," and that steam as it expands exerts less and less pressure. This is important in the steam-engine. Pascal and the Hydraulic Press It was Blaise Pascal, a Frenchman, who proved beyond the possibility of a doubt that air-pressure supports the mercury in a barometer, and lifts the water in a pump (Fig. 7). He had two mercury barometers exactly alike set up at the foot of a mountain. The mercury stood at the same height in each. Then one barometer was left at the foot of the mountain, and the other was carried to the summit, about three thousand feet high. The mercury in the second barometer then stood more than three inches lower than at first. As the barometer was carried down the mountain the mercury slowly rose until, at the foot, it stood at the same height as at first. The party stopped about half-way down the mountain, allowing the barometer to rest there for some time, and observing it carefully. They found that the mercury stood about an inch and a half higher than at the foot of the mountain. During all this time the height of the mercury in the barometer which had been left at the foot of the mountain did not change. [Illustration: FIG. 7--A LIFT-PUMP Air pressing down on the water in the well causes the water to rise in the pump. The air can do this only when the plunger is at work removing air or water and reducing the pressure inside the pump.] It is now known that when a barometer is carried up to a height of nine hundred feet, the mercury stands an inch lower than at the earth's surface. For every nine hundred feet of elevation the mercury is lowered about one inch. In this way the height of a mountain can be measured, and a man in a balloon or an air-ship can tell at what height he is sailing. For this purpose, however, a barometer is used that is more easily carried than a mercury barometer. Pascal invented the hydraulic press, a machine with which he said he could multiply pressure to any extent, which reminds us of Archimedes' saying that, with his own hand, he could move the earth if only he had a place to stand. Pascal could so arrange his machine that a man pressing with a force of a hundred pounds on the handle could produce a pressure of many tons. In fact, a man can so arrange this machine that he can lift any weight whatever (Fig. 8). [Illustration: FIG. 8--A SIMPLE HYDRAULIC PRESS A one-pound weight holds up a hundred pounds.] The hydraulic press has two cylinders. One cylinder must be larger than the other. The two cylinders are filled with a liquid, as water or oil, and are connected by a tube so that the liquid can flow from one cylinder into the other. There is a tightly fitting piston in each cylinder. If one piston has an area of one square inch, and the other has an area of one hundred square inches, then every pound of pressure on the small piston causes a hundred pounds of pressure on the large piston. A hundred pounds on the small piston would lift a weight of ten thousand pounds on the large piston. But we can see that the large piston cannot move as fast as the small one does. Though we can lift a very heavy weight with this machine, we must expect this heavy weight to move slowly. There must be a loss in speed to make up for the gain in the weight lifted (Fig. 9). An hydraulic press with belt-driven pump is illustrated in Fig. 10. [Illustration: FIG. 9--HOW AN HYDRAULIC PRESS WORKS One man with the machine can exert as much pressure as a hundred men could without the machine. The arrows show the direction in which the liquid is forced by the action of the plunger _p_. The large piston _P_ is forced up, thus compressing the paper.] [Illustration: FIG. 10--AN HYDRAULIC PRESS WITH BELT-DRIVEN PUMP] Newton Sir Isaac Newton as a boy did not show any unusual talent. In school he was backward and inattentive for a number of years, until one day the boy above him in class gave him a kick in the stomach. This roused him and, to avenge the insult, he applied himself to study and quickly passed above his offending classmate. His strong spirit was aroused, and he soon took up his position at the head of his class. It was his delight to invent amusements for his classmates. He made paper kites, and carefully thought out the best shape for a kite and the number of points to which to attach the string. He would attach paper lanterns to these kites and fly them on dark nights, to the delight of his companions and the dismay of the superstitious country people, who mistook them for comets portending some great calamity. He made a toy mill to be run by a mouse, which he called the miller; a mechanical carriage, run by a handle worked by the person inside, a water-clock, the hand of which was turned by a piece of wood which fell or rose by the action of dropping water. At the age of fifteen, his mother, then a widow, removed him from school to take charge of the family estate. But the farm was not to his liking. The sheep went astray, and the cattle trod down the corn while he was perusing a book or working with some machine of his own construction. His mother wisely permitted him to return to school. After completing the course in the village school he entered Trinity College, Cambridge. Gravitation It was in the year following his graduation from Cambridge that he made his greatest discovery--that of the law of gravitation. A plague had broken out in Cambridge, to escape which Newton had retired to his estate at Woolsthorpe. Here he was sitting one day alone in the garden thinking of the wonderful power which causes all bodies to fall toward the earth. The same power, he thought, which causes an apple to fall to the ground causes bodies to fall on the tops of the highest mountains and in the deepest mines. May it not extend farther than the tops of the mountains? May it not extend even as far as the moon? And, if it does, is not this power alone able to hold the moon in its orbit, as it bends into a curve a stone thrown from the hand? There followed a long calculation requiring years to complete. Seeing that the results were likely to prove his theory of gravitation, he was so overcome that he could not finish the work. When this was done by one of his friends, it was found that Newton's thought was correct--that the force of gravitation which causes bodies to fall at the earth's surface is the same as the force which holds the moon in its orbit. As the earth and moon attract each other, so every star and planet attracts every other star
{'title': 'The Story of Great Inventions by Elmer Ellsworth Burns', 'source': 'Project Gutenberg', 'lang': 'en'}