  Illustrated Capital W Where do we find water? We find water almost everywhere; above the earth, on the earth, and beneath the earth’s surface. Where do we find water above the earth? We find it in the air, in the form of vapor. Where do we find water on the earth? We find it in springs, in streams of water, and in lakes and oceans. Where else is water on the earth? It is in the sap of plants, the juice of fruits, and the blood of animals. Where do we find water beneath the earth’s surface? We find it in streams running in every direction. Has water any influence on climate? Yes; water causes many changes in climate. What changes does water produce in climate? It makes spring and summer cooler, and autumn and winter warmer. How does water make the Spring of the year cooler? The ice and snow while melting, take up a large amount of heat, which passes into the water as latent heat. Where does the melting ice and snow obtain this heat? They obtain it from the air, and from objects near the surface of the earth. What advantage is derived from this? The tender buds and blossoms are kept back in the spring until the ice and the snow are melted, and the earth becomes warmed, so that they are seldom injured by the cold. How does water make Summer cooler? By the streams, lakes, and oceans, which absorb heat from the sun; and, as the water is a poor radiator, but little of this heat is given off to the air. What effect does this heat produce upon the water? The temperature of the water is gradually increased by it during the hot weather of summer. How is this useful? It gives heat to the plants in the water, so that they may grow; and it rouses into active life, the fish and other breathing things, from the torpid state in which they are during winter. Does water store away a large amount of heat? It does; and thus the summer is made much cooler. How does water make Autumn warmer? In the autumn the heat in the water is given off, so that the air is kept warmer than it would otherwise be. How does this affect autumn weather? It makes that season of the year mild and pleasant. What advantage is derived from this? It gives the late fruits and seeds a chance to ripen; and it affords time for the sap of plants to return to the roots, and to become prepared for the frosts of winter. How does water make Winter warmer? By being changed into ice and snow. When water is changed into ice or snow, what takes place? The latent heat in the water is given off, and thus the winter air is made warmer. Can water be compressed into a smaller bulk? Yes; it can be compressed, but not so much as air. What is said of water that is compressed? Its particles are pressed closer together, and it is said to be more dense. Why is the water at the bottom of a pond more dense than that at the surface? Because the water at the bottom of the pond has to bear the weight of all the water above it. Is the weight of the water very great? The weight of the water is very great. What is its weight at the depth of one hundred feet? At the depth of one hundred feet, it presses in every direction, with a force of forty-three pounds on every square inch of surface. What is its weight in the ocean at the depth of one mile? At the depth of one mile it presses in every direction, When one opening is made near the top, and another near the bottom of a vessel full of water, from which will the water flow with the most force? From the opening near the bottom of the vessel. Why is this? Because there is more weight of water to press it out from the opening near the bottom. When water is poured into a vessel, what becomes of it? It spreads out so that its surface is level. When different vessels are connected together, what does the water do? It falls to the same level in all of them. How high will the tea stand in the spout of a tea-pot? Just as high as the tea is in the tea-pot. Fig. 20. Will the tea in the spout balance that in the tea-pot? The tea in the spout will balance that in the tea-pot, as is shown in Fig. 20. How else can it be shown that water will rise to the same level in different vessels? By a reference to Fig. 21, this may be seen. Fig. 21. Let these vessels be made so as to connect with each other by the tube at the bottom; then, when water is poured into one of them, it will rise up in each of the others, so as to be the same height in all. Where is this principle used to benefit mankind? It is used in supplying the inhabitants of cities with water. What must be built in order to supply a city with water? A reservoir must be built. What is a reservoir? It is a large basin made so as to hold water. How high is the water in the basin? It is usually as high as the tops of the houses in the city. How is the water raised into the basin? It is raised into the basin by means of pumps. How is the water conveyed from the basin to the houses in the city? By means of pipes laid under the surface of the earth, and extending to all parts of the city. How high will the water rise in these pipes? Nearly as high as it is in the basin. If an opening be made in a pipe, how high will the water be forced up? Nearly as high as the water in the basin. What is the water flowing from such an opening called? It is called a fountain. What makes the water shoot up in a fountain? The pressure of the water in the basin forces it to shoot up in the fountain. To what does water always tend? Water always tends to fall to a level. What instrument is constructed on this principle? The water-level. What is a water-level? It is a glass tube so nearly filled with water that it contains only a bubble of air. This tube is fastened in a piece of wood, as shown in Fig. 22. Fig. 22. How can we tell when the instrument is level? By the bubble of air, which will always be at the centre of the tube when it is level. What other liquid may be used to fill the tube? Alcohol may be used to fill the tube, and it is then called a spirit-level. Of what use is the spirit-level? It is used for levelling the walls and wood-work of houses, bridges, and other structures. Springs and Streams.When we dig into the earth, can we always find water? Yes; we can always find water. What reason may be given for believing this? Because thousands of wells have been dug in different parts of the country, and water is obtained from them. Are these wells all of the same depth? No; they vary in depth from four or five feet to eighty or ninety feet. What makes the water hard in some wells? When the stream of water passes through iron ore, before reaching the well, it absorbs some of the iron, which makes it hard. How else may it become hard? By passing through other mineral substances, such as limestone and sulphur, it will become hard. Why is the water in some wells much warmer than in others? In wells where the water is warm, the streams flowing into them are near the surface of the earth, and are heated by the sun; but in the wells of cold water, the streams are much deeper in the earth. When these streams flow out at the surface of the earth, what are they called? They are called springs. Where are springs found? They are mostly found on hill-sides, or in valleys; but they are sometimes found on the top of the hills. Why is the water in some springs warmer than in others? In springs where the water is warm, the streams flowing into them are so near the surface of the earth as to be warmed by the sun, while in springs where the water is colder, the streams are much deeper in the earth. What becomes of the water in the springs? It runs away down the valleys, forming brooks and creeks. When these brooks and creeks flow into other brooks and creeks, what do they form? They form lakes and rivers. Into what do the rivers flow? The rivers flow into the ocean. How are waves produced? Waves are produced by the winds blowing against the surface of the water. What does a light wind produce? A light wind produces only ripples on the surface of the water. What does a stronger wind produce? A stronger wind produces waves in the water. Why is the water of the ocean and the larger lakes seldom at rest? Because the wind touching the water seldom ceases to blow. To what depth does the wind disturb the water of the ocean? Wind seldom disturbs the ocean to a greater depth than thirty feet below its surface. Fogs and Clouds.What is always taking place from the surface of the water in the rivers, lakes, and oceans? The water is always passing off in the form of vapor. Where does this vapor go? It goes into the air so that the air becomes filled with moisture. What kind of air will hold the most vapor? Warm air will hold the most vapor. When warm air becomes colder, what is done with the vapor? The vapor is condensed into small particles of water. When this takes place near the earth, what does it produce? It produces a fog. Where do fogs mostly occur? Fogs mostly occur over low grounds and along the course of streams. When the vapor is condensed higher up in the air, what does it produce? It produces a cloud. What is a cloud? A cloud is only a fog, higher up in the air. Do fogs ever ascend in the air? Yes; they often ascend, and thus produce clouds. What causes the vapor of the air to be condensed into clouds? Cold causes it to be condensed into clouds. Does the air grow colder as we ascend? Yes; the higher we ascend, the colder we find the atmosphere. What becomes of the vapor in the air, as it ascends from the earth? The vapor is condensed into clouds in the upper regions of the air. Why do we mostly see clouds at the top of a mountain? Because the vapor in the air is condensed into clouds by the cold at the top of the mountain. When is a cloud formed in the air? When a warm, damp wind meets with a cold wind, its vapor is condensed and a cloud is formed. Are clouds often formed in this way? Yes; clouds are often quickly formed in this way. When the cloud passes into a warmer current of air, what becomes of it? It is changed back into vapor, so that it cannot be seen. How then can a cloud in the sky disappear very quickly? By passing into a warmer current of air the cloud is changed into a vapor, and may thus quickly disappear. Are clouds of different heights? Yes; some clouds touch the earth, while other clouds are high up in the air. Why are clouds higher on a fine day? Because there is not so much moisture in the air, and, therefore, it rises higher before its vapor is condensed into clouds. Why are clouds lower on a rainy day? Because there is so much moisture in the air, that it is condensed into clouds near the earth. Are the clouds high during a thunder-storm? No; during a thunder-storm the clouds are seldom more than one-third of a mile high, and very often are much nearer the surface of the earth. Is there any difference in the thickness of the clouds? Yes; some are only a few inches thick, while others are a mile or more in thickness. When the sun is about to rise, which of the seven colors of light is the first to appear? The red color appears first. When the sun sets, which of the seven colors is the last to fade away? The red color is the last to fade away. Why are the clouds red just before sunrise? Because they are tinged by the red ray of light, before the other rays appear. Why are the clouds red after sunset? Because they are tinged by the red ray of light, after the other rays have faded away. Dew.What is dew? Dew is the moisture that collects on plants and other objects, during the night. What causes dew upon any object? The air in contact with that object has its vapor condensed, so that the water is deposited on it in the form of dew. Does the same quantity of dew collect upon all objects? No; it collects much more upon some objects than upon others. Upon what objects does it collect the most? Upon those which radiate or give off heat the best. Why do objects that are good radiators, collect the most dew? Because they give off their heat rapidly after sunset, and before morning, become so cold that they condense the vapor in the air touching them, and cause the dew to be deposited on their surfaces. What objects are the best radiators of heat? Grass, wood, the leaves of plants, and, in fact, all things of a vegetable nature. What objects then collect the most dew? Plants collect the most dew. Of what use is the dew to plants? It supplies them with moisture, and answers in the place of rain. When do we have the heaviest dew? When the air is still and the sky is free from clouds. Why does wind prevent the deposit of dew? Because the air in contact with the grass and other objects, is removed so quickly that it does not get cool enough to deposit dew. Why are dews heaviest when the air is still? Because the air remains in contact with the grass and other objects, until it is cool enough to deposit the dew. Why is there but little dew on a cloudy night? Because the clouds prevent radiation of heat from the earth; hence, the earth and the objects near it, remain too warm to cause any dew. Why is there a heavy dew on a clear night? Because there is nothing then to prevent free radiation of heat from the earth; hence, it soon cools so as to cause a heavy dew. How may dew be prevented from forming on any object? By placing a cover over that object. How does a cover prevent the formation of dew? It prevents the object that is covered from giving off its heat, so that it does not get cool enough to cause a deposit of dew. Why is there but little dew under trees? Because trees prevent the free radiation of heat from the objects beneath them; hence, but little dew is formed under trees. Why do stone walls sweat? Because the walls cool the air in contact with them, so that its vapor is condensed into water, and deposited on the walls. Why does the sweating of stones indicate rain? Because it shows that the air contains a large amount of moisture. When is a vessel of water said to sweat? When drops of water collect on the outside of the vessel, it is said to sweat. Why does a pitcher of cold water sweat? Because the vapor in the air in contact with the cold pitcher is condensed into moisture, and deposited on the pitcher. Why does the pitcher sweat most before a rain? Because the air then contains a large quantity of moisture. Why will not the pitcher sweat in fine weather? Because the air contains only a small quantity of moisture in fine weather. Why does moisture sometimes collect on a glass window in a warm room? Because the glass cools the air, and causes its moisture to collect in small drops on the glass. What makes the glass cold enough to condense the vapor in the air? The cold air, outside of the room, in contact with the glass. Where does the moisture in the air of the warm room come from? It comes from the breath of persons, and from the steam of the tea-kettle. When the breath is blown on a cold object, like a piece of glass or metal, what is the result? The moisture in the breath is condensed by the cold object, and is collected in small drops of water on its surface. Frost.When the temperature of the air is reduced below thirty-two degrees, what becomes of the moisture collected on plants and other things? The moisture is frozen. What is this frozen moisture called? It is called frost. What then is frost? Frost is the frozen moisture on the walls and window panes, and the frozen dew on plants and other objects. On what objects do we find the most frost? The most frost is found on objects having the most dew. What is a heavy dew when frozen called? It is called a hoar-frost. When do we have a hoar-frost? We have heavy frosts when the air is full of moisture. Why does a heavy frost indicate rain or snow? Because it shows that the air contains much moisture. Are heavy frosts usually followed by rain or snow? Yes; a heavy frost, on two successive mornings, is mostly followed by rain or snow within a few hours. Rain, Snow, and Hail.What is a mist? A mist is very small drops of water falling through the air. When these drops are larger, what is it called? It is called rain. What causes rain? Rain is caused by the sudden cooling of the air above the earth. How does cooling the air cause rain? The cold condenses the vapor in the air, so that its moisture is forced out in drops, which fall to the earth. What becomes of the rain falling upon the earth? A part of it remains on the surface of the earth, and is either absorbed again by the air, or is carried away to the ocean by the creeks and rivers. What becomes of the remaining part? It sinks into the earth, to furnish moisture to the roots of plants, and to supply the streams beneath the earth’s surface with water. How does rain purify the air? By washing away many things that would, if left, decay and make the air impure and unhealthy. When the air is cooled below thirty-two degrees, what becomes of the moisture in it? The moisture in it is frozen. What is this frozen moisture in the air called? It is called snow. What are the particles of snow called? They are called snow-flakes. Are these snow-flakes all alike? No; they vary very much in size and shape. What does Fig. 23 represent? It represents a few of the various and beautiful forms of the snow-flake or snow-crystals. Fig. 23. At what temperature of the air does snow usually fall? At a temperature of about thirty-two degrees. Is there any reason for the remark that it is “too cold to snow”? Yes; for it seldom snows when the temperature of the air is much below thirty-two degrees. Of what use is snow? The snow is a warm covering for the earth. Why is snow a warm covering for the earth? Because the air in the snow makes it a poor conductor What is hail? Drops of rain, when frozen, are called hail. How is hail formed? The rain-drops are frozen as they fall through the air; hence, the hail-stones of winter are no larger than the rain-drops. When have we dew? When the air in contact with the earth or the plants is cooled, its vapor is condensed into dew. When have we frost? When the air in contact with the earth or the plants is cooled below thirty-two degrees, its vapor is condensed into dew, and the dew is frozen into frost. When have we fog? When the air near the earth is slightly cooled, its vapor is condensed into fog. When have we clouds? When the air higher above the earth is slightly cooled, its vapor is condensed into clouds. When have we mist? When the air is a little more cooled, its vapor is condensed and mist falls. When have we rain? When the air is still more cooled, its vapor is condensed and rain falls. When have we snow? When the air is cooled below thirty-two degrees, its vapor is condensed and frozen into snow. When have we hail? When the rain-drops, while falling, pass through a current of air cold enough to freeze them, hail is produced. Ice.What is ice? Ice is frozen water. When does water freeze? Water freezes when its temperature is reduced to thirty-two degrees. Is water increased in bulk by freezing? Water is increased in bulk by freezing. Why do water-pipes often burst in cold weather? The water in them freezes, and as it increases in bulk, the pipes burst. Why are some springs never frozen? Because water, much above the freezing-point, is always flowing into them from the earth, and thus they are kept too warm to freeze. Why are some other springs frozen? Because the water flowing into them comes from near the surface of the earth, and is soon made cold enough to freeze. Does salt water freeze at the same temperature as fresh water? No; fresh water freezes at thirty-two degrees, but How is this useful? The surface of the ocean is never frozen over except in very cold latitudes; hence, vessels may sail on it at all seasons of the year, and carry the products of one country to another; thus adding much to our comfort and our enjoyment. Horse. Decoration.
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