  Illustrated Capital W When a cat’s back is rubbed in the dark, what does it give off? It gives off small sparks. What are these small sparks called? They are called electric sparks, or electricity. If a horse be rubbed in the winter when it is dark, what will be given off from him? Electricity will be given off from the horse. When sealing-wax is rubbed with a silk handkerchief, or a piece of flannel, what is produced? Electricity is produced in the sealing-wax. What will this electricity in the sealing-wax do? It will attract bits of paper, straw, feathers, and hairs, when it is held near them. What other substance will act the same as the sealing-wax? A dry glass tube will act in the same manner when rubbed. Where is electricity found? Electricity is found in every body, and in every thing. How is electricity developed? Electricity is developed by motion, by friction, and by almost every change that takes place. Is electricity found in the air? Yes; the air is almost constantly electrified. With what is electricity often accompanied? Electricity is often accompanied by heat and light. How many kinds of electricity are there? There are two kinds of electricity. What are they called? They are called positive and negative electricity. What do these two kinds of electricity always do? They always attract each other. When one body contains positive and the other body negative electricity, what will the two bodies do? They will rush together. When both bodies are positive or both are negative, what will they do? They will repel each other. When a body permits electricity to pass freely through it, what is it called? It is called a good conductor of electricity. What substances are good conductors of electricity? Metals, charcoal, water, animals, vegetables, flame, and smoke. When a body does not permit the electricity to pass through it, what is it called? It is called a non-conductor of electricity. What substances are non-conductors of electricity? Gutta-percha, sulphur, glass, silk, wool, hair, feathers, cotton, and paper. What is lightning? Lightning is electricity passing from one place to another. When does lightning pass from one cloud to another cloud? Whenever one cloud becomes filled with more electricity than another, the cloud having the most electricity gives off a portion to the cloud having the least electricity. When does lightning pass from the earth to a cloud? Whenever the earth contains more electricity than the cloud does. When does lightning pass from a cloud to the earth? Whenever the cloud contains more electricity than the earth does. How near are the clouds when the lightning comes to the earth? The clouds are seldom half a mile away when the lightning comes from them to the earth. What noise is made by the lightning? The lightning passes so quickly through the air, that it makes a noise called thunder. Do we always hear the thunder when there is lightning? No; the lightning is sometimes so far away that the thunder cannot be heard. What bodies attract the lightning to the earth? Tall trees, steeples, high houses, and mountains. Does the lightning do any harm? Yes; it does much harm by destroying trees, houses, animals, and, indeed, almost everything in its course. What does lightning sometimes do with buildings? It sets the buildings on fire so that they are burned. How are buildings protected from injury by lightning? They are protected by means of the lightning-rod, which was invented by Dr. Franklin. Of what is the lightning-rod made? The lightning-rod is made of some metal, usually of iron or copper, which is a good conductor of electricity. What does the lightning-rod do when the building is struck? The lightning-rod conducts the electricity to the earth, so that it does not injure the building. Must the lightning-rod be higher than the building? Yes; because the lightning is apt to strike the highest object. Of what should the point of the rod be made? The point should be made of silver or platinum, so that it will always remain bright. Should the rod extend deep into the ground? The rod should extend four or five feet beneath the surface of the earth. Why should ashes or charcoal be put around the bottom of the rod? Because they are good conductors and will help to conduct the lightning into the earth. How large should the lightning-rod be? If made of iron, the lightning-rod should be about three-fourths of an inch in diameter. Why is glass put around the rod where it is joined to the building? The glass is a non-conductor, and prevents the lightning from leaving the rod. Why is it not safe to stand near a fire during a thunder-storm? Because the fire is a good conductor, and sometimes draws the electricity into the room. What part of the room is the safest place? The middle of a room is thought to be the safest place. Is a feather-bed a safe place? Yes; because the feathers are a non-conductor, and will not attract the lightning. Is dry air a non-conductor of electricity? Yes; dry air is a non-conductor of electricity. When are thunder-storms most frequent? Thunder-storms are more frequent in summer than in winter, and more so in the afternoon than in the morning. By what are thunder-storms usually attended? They are usually attended by some change in the direction of the wind. Where do thunder-storms generally prevail? They generally prevail in the lower regions of the air, near the earth. What is the rapidity of lightning? The rapidity of lightning is probably not less than 250,000 miles in a second, and the flash does not exceed the millionth part of a second in duration. Magnetism.Of what does magnetism treat? Magnetism treats of the property of magnets. What is a magnet? A magnet is a piece of iron ore having the power of attracting iron and steel. How many kinds of magnets are there? There are two kinds of magnets: natural magnets, and artificial magnets. What other name is given to a natural magnet? It is called a loadstone. Where are natural magnets or loadstones found? They are dug out of the earth, and are found most abundantly in Norway and Sweden. What is an artificial magnet? An artificial magnet is one made by magnetizing a bar of steel. How may a bar of steel be magnetized? A bar of steel, when rubbed on a natural magnet, becomes magnetized. When the bar of steel is bent in the shape of a horse-shoe, what is it called? It is then called a horse-shoe magnet, from its shape. Where does a magnetic bar always point, when it is made to move easily on a pivot? One end of it always points to the north, and the other end to the south. What are the ends of the magnet called? The north end is called the positive, and the south end is called the negative. What is there curious about the magnet? The positive end of one magnet always attracts the Why are artificial magnets made of steel? Because steel will remain magnetized, but iron soon loses the magnetic properties. What is a compass? A compass is an instrument containing a magnetic needle, so balanced as to move easily on a pivot. In what direction does this needle always point? This needle always points toward the north. By whom is the compass used? It is used by travellers to guide them on their journey; by surveyors to mark out the boundary lines between different properties; and by seamen to point out their way across the sea from one place to another. Before the Mariner’s Compass was invented, seamen were afraid to venture out of the sight of land, for fear of being lost on the ocean; for they then had no means of telling where they were, or in what direction to guide their vessels, so as to reach the land again. Electro-Magnetism.Are magnetism and electricity much alike? Yes; they are so nearly alike that many persons think they are identical. What is an electro-magnet? An electro-magnet is a magnet obtained by means of electricity. Of what is the magnet made? The magnet is made of soft iron, around which are How is the soft iron made into a magnet? The iron is magnetized by the passage of electricity through the wire. Of what use is this magnet? It is used in the electro-magnetic telegraph. When and where was the first line of telegraph built? The first line of telegraph was built in 1844, from Washington to Baltimore, by Professor Morse. What is the principle of the telegraph? At one end of the telegraph wire is an electrical battery, and at the other end is an electro-magnet. When a message is to be sent, the electricity is transmitted through the wire to the soft iron of the electro-magnet, which causes the iron to move, and this motion is conveyed to the machinery, which is needed to print the message in letters or signals, so as to be understood. Does electricity move rapidly? Yes; its velocity is such as to move around the earth in a quarter of a second. What is the electrical battery called? The electrical battery is called a key. What is the electro-magnet called? The electro-magnet is called a receiver. For what are the key and receiver used? The key is used for sending messages, and the receiver for receiving them. What must each station have? Each station must have both a key and a receiver, so as to send as well as receive messages. What is the Atlantic cable? The Atlantic cable is a telegraphic wire reaching across the Atlantic Ocean, from America to Europe. When was the first Atlantic cable laid? The first Atlantic cable was successfully laid in 1866, between Newfoundland and Ireland. It is eighteen hundred and sixty-four miles long, and its success is chiefly due to Cyrus W. Field. Of what use is the Atlantic cable? The Atlantic cable forms a telegraphic connection between Europe and America, so that news may be sent from one country to the other in a few moments of time; thus the people of the two continents, although so far apart, can communicate with each other many times in a single day. By E. J. HOUSTON, A.M., This book is intended for Graded Schools, Academies, Seminaries, Normal Schools, etc. It gives the elements of the science in a concise form and in logical sequence, so that the book forms a system of Natural Philosophy, and not a mere collection of disconnected facts. It is fully “up to the times” in every respect, and gives full descriptions of the more important discoveries lately made in Physical Science; the Electric Light, the Telephone, the Microphone, the Phonograph, etc., are all described and illustrated. An examination of the work will show that no expense has been spared to bring it up to the highest standard as regards illustration and typography. We invite the attention of Teachers to our Publications, a Catalogue of which will be sent on application. On our List will be found some of the most popular of modern Text-Books. Please address Eldredge & Bro., MORGAN & HANFORD. ELDREDGE & BROTHER |
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