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+The Project Gutenberg EBook of Diggers in the Earth, by Eva March Tappan
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Diggers in the Earth
+
+Author: Eva March Tappan
+
+Release Date: March 6, 2008 [EBook #24762]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK DIGGERS IN THE EARTH ***
+
+
+
+
+Produced by Diane Monico and The Online Distributed
+Proofreading Team at https://www.pgdp.net (This file was
+produced from images generously made available by The
+Internet Archive/American Libraries.)
+
+
+
+
+
+
+
+
+
+THE INDUSTRIAL READERS
+
+_Book II_
+
+DIGGERS IN THE
+EARTH
+
+BY
+
+EVA MARCH TAPPAN, Ph.D.
+
+_Author of "England's Story," "American Hero Stories,"
+"Old World Hero Stories," "Story of the Greek People,"
+"Story of the Roman People," etc. Editor of
+"The Children's Hour."_
+
+[Illustration]
+
+HOUGHTON MIFFLIN COMPANY
+
+BOSTON   NEW YORK   CHICAGO
+
+
+
+
+THE INDUSTRIAL READERS
+
+By Eva March Tappan
+
+  I. THE FARMER AND HIS FRIENDS. 50 cents.
+
+ II. DIGGERS IN THE EARTH. 50 cents.
+
+III. MAKERS OF MANY THINGS. 50 cents.
+
+ IV. TRAVELERS AND TRAVELING. 50 cents.
+
+The foregoing are list prices, postpaid
+
+
+COPYRIGHT, 1916, BY EVA MARCH TAPPAN
+ALL RIGHTS RESERVED
+
+_First printing April 1916;_
+_Reprinted December 1916_
+
+
+The Riverside Press
+CAMBRIDGE, MASSACHUSETTS
+U. S. A.
+
+
+
+
+PREFACE
+
+
+The four books of this series have been written not merely to provide
+agreeable reading matter for children, but to give them information.
+When a child can look at a steel pen not simply as an article
+furnished by the city for his use, but rather as the result of many
+interesting processes, he has made a distinct growth in intelligence.
+When he has begun to apprehend the fruitfulness of the earth, both
+above ground and below, and the best way in which its products may be
+utilized and carried to the places where they are needed, he has not
+only acquired a knowledge of many kinds of industrial life which may
+help him to choose his life-work wisely from among them; but he has
+learned the dependence of one person upon other persons, of one part
+of the world upon other parts, and the necessity of peaceful
+intercourse. Best of all, he has learned to see. Wordsworth's familiar
+lines say of a man whose eyes had not been opened,--
+
+    "A primrose by a river's brim
+    A yellow primrose was to him,
+    And it was nothing more."
+
+These books are planned to show the children that there is "something
+more"; to broaden their horizon; to reveal to them what invention has
+accomplished and what wide room for invention still remains; to teach
+them that reward comes to the man who improves his output beyond the
+task of the moment; and that success is waiting not for him who works
+because he must, but him who works because he may.
+
+Acknowledgment is due to the Lehigh Valley Railroad, Jones Brothers
+Company, Alpha Portland Cement Company, Dwight W. Woodbridge, the Utah
+Copper Company, the Aluminum Company of America, the Diamond Crystal
+Salt Company, T. W. Rickard, and others, whose advice and criticism
+have been of most valuable aid in the preparation of this volume.
+
+                                     EVA MARCH TAPPAN.
+
+
+
+
+CONTENTS
+
+   I. IN A COAL MINE                                   1
+
+  II. DOWN IN THE QUARRIES                            11
+
+ III. HOUSES OF SAND                                  21
+
+  IV. BRICKS, THEIR FAULTS AND THEIR VIRTUES          31
+
+   V. AT THE GOLD DIGGINGS                            39
+
+  VI. THE STORY OF A SILVER MINE                      48
+
+ VII. IRON, THE EVERYDAY METAL                        57
+
+VIII. OUR GOOD FRIEND COPPER                          65
+
+  IX. THE NEW METAL, ALUMINUM                         76
+
+   X. THE OIL IN OUR LAMPS                            84
+
+  XI. LITTLE GRAINS OF SALT                           95
+
+
+
+
+LIST OF ILLUSTRATIONS
+
+
+A STRUCTURAL STEEL APARTMENT BUILDING                 vi
+
+HOW A COAL MINE LOOKS ABOVEGROUND                      5
+
+MINERS AND THEIR MINE                                 10
+
+OPENING A GRANITE QUARRY                              13
+
+BUILDING A CONCRETE ROAD                              27
+
+IN A NEW JERSEY BRICK MILL                            33
+
+HYDRAULIC GOLD MINING                                 41
+
+THE STORY OF A SPOON                                  51
+
+IN THE STEEL FOUNDRY                                  61
+
+IN A COPPER SMELTER                                   67
+
+A "MOVIE" OF AN ALUMINUM FUNNEL                       79
+
+A CALIFORNIA OIL FIELD                                87
+
+
+
+
+[Illustration: A STRUCTURAL STEEL APARTMENT BUILDING
+
+_Courtesy American Bridge Co._
+
+First the steel frame, then the floors, then the stone or brick shell,
+then the interior finishing--this is how the building is made.]
+
+
+
+
+THE INDUSTRIAL READERS
+
+BOOK II
+
+DIGGERS IN THE EARTH
+
+
+
+
+I
+
+IN A COAL MINE
+
+
+Did you ever wonder how beds of coal happened to be in the earth? This
+is their story.
+
+Centuries ago, so many thousand centuries that even the most learned
+men can only guess at their number, strange things were coming to
+pass. The air was so moist and cloudy that the sun's rays had hard
+work to get through. It was warm, nevertheless, for the crust of the
+earth was not nearly so thick as it is now, and much heat came from
+the earth itself. Many plants and trees grow best in warm, moist air;
+and such plants flourished in those days. Some of their descendants
+are living now, but they are dwarfs, while their ancestors were
+giants. There is a little "horse-tail" growing in our meadows, and
+there are ferns and club mosses almost everywhere. These are some of
+the descendants; but many of their ancestors were forty or fifty feet
+high. They grew very fast, especially in swamps; and when they died,
+there was no lack of others to take their places. Dead leaves fell and
+heaped up around them. Stumps stood and decayed, just as they do in
+our forests to-day. Every year the soft, black, decaying mass grew
+deeper. As the crust of the earth was so thin, it bent and wrinkled
+easily. It often sank in one place and rose in another. When these
+low, swampy places sank, water rushed over them, pressing down upon
+them with a great weight and sweeping in sand and clay. Now, if you
+burn a heap of wood in the open air, the carbon in the wood burns and
+only a pile of ashes remains. "Burning" means that the carbon in the
+wood unites with the oxygen gas in the air. If you cover the wood
+before you light it, so that only a little oxygen reaches it, much of
+the carbon is left, in the form of charcoal.
+
+When wood decays, its carbon unites with the oxygen of the air; and so
+decay is really a sort of burning. In the forests of to-day the
+leaves, and at length the trees themselves, fall and decay in the open
+air; but at the time when our coal was forming, the water kept the air
+away, and much carbon was left. This is the way coal was made. Some of
+the layers, or strata, are fifty or sixty feet thick, and some are
+hardly thicker than paper. On top of each one is a stratum of
+sandstone or dark-gray shale. This was made by the sand and mud which
+were brought in by the water. These shaly rocks split easily into
+sheets and show beautiful fossil impressions of ferns. There are also
+impressions of the bark and fruit of trees, together with shells,
+crinoids, corals, remains of fishes and flying lizards, and some few
+trilobites,--crablike animals with a shell somewhat like the back of
+a lobster, but marked into three divisions or lobes, from which its
+name comes.
+
+Since the crust of the earth was so thin and yielding, it wrinkled up
+as the earth cooled, much as the skin of an apple wrinkles when the
+apple dries. This brought some of the strata of coal to the surface,
+and after a while people discovered that it would burn. If a vein of
+coal cropped out on a man's farm, he broke some of it up with his
+pickaxe, shoveled it into his wheelbarrow, and wheeled it home. After
+a while hundreds of thousands of people wanted coal; and now it had to
+be mined. In some places the coal stratum was horizontal and cropped
+out on the side of a hill, so that a level road could be dug straight
+into it. In other places the coal was so near the surface that it
+could be quarried under the open sky, just as granite is quarried.
+Generally, however, if you wish to visit a coal mine, you go to a
+shaft, a square, black well sometimes deeper than the height of three
+or four ordinary church steeples. You get into the "cage," a great
+steel box, and are lowered down, down, down. At last the cage stops
+and you are at the bottom of the mine. The miners' faces, hands,
+overalls, are all black with coal dust. They wear tiny lamps on their
+caps, and as they come near the walls of coal, it sparkles as it
+catches the light. Here and there hangs an electric lamp. It is doing
+its best to give out light, but its glass is thick with coal dust. The
+low roof is held up by stout wooden timbers and pillars of coal. A
+long passageway stretches off into a blacker darkness than you ever
+dreamed of. Suddenly there is a blaze of red light far down the
+passage, a roar, a medley of all sorts of noises,--the rattling of
+chains, the clattering of couplings, the shouts of men, the crash of
+coal falling into the bins. It is a locomotive dragging its line of
+cars loaded with coal. In a few minutes it rushes back with empty cars
+to have them refilled.
+
+All along this passageway are "rooms," that is, chambers which have
+been made by digging out the coal. Above them is a vast amount of
+earth and rock, sometimes hundreds of feet in thickness. There is
+always danger that the roof will cave in, and so the rooms are not
+made large, and great pillars of coal are left to hold up the roof.
+
+Not many years ago the miner used to do all the work with his muscles;
+now machines do most of it. The miner then had to lie down on his side
+near the wall of coal in his "room" and cut into it, close to the
+floor, as far as his pickaxe would reach. Then he bored a hole into
+the top of the coal, pushed in a cartridge, thrust in a slender squib,
+lighted it, and ran for his life. The cartridge exploded, and perhaps
+a ton or two of coal fell. The miner's helper shoveled this into a car
+and pushed it out of the room to join the long string of cars.
+
+[Illustration: HOW A COAL MINE LOOKS ABOVEGROUND
+
+All that shows on the surface is the machinery shed where the various
+engines work to keep the air fresh, and bring up the miners and the
+coal.]
+
+That is the way mining used to be done. In these days a man with a
+small machine for cutting coal comes first. He puts his cutter on the
+floor against the wall of coal and turns on the electricity. _Chip,
+chip_, grinds the machine, eating its way swiftly into the coal, and
+soon there is a deep cut all along the side of the room. The man and
+his machine go elsewhere, and the first room is left for its next
+visitors. They come in the evening and bore holes for the blasting.
+Once these holes were bored by hand, but now they are made with
+powerful drills that work by compressed air. A little later other men
+come and set off cartridges. In the morning when the dust has settled
+and the smoke has blown away, the loaders appear with their shovels
+and load the coal into the cars. Then it is raised to the surface and
+made ready for market.
+
+Did you ever notice that some pieces of coal are dull and smutty,
+while others are hard and bright? The dull coal is called bituminous,
+because it contains more bitumen or mineral pitch. This is often sold
+as "run-of-mine" coal,--that is, just as it comes from the mine,
+whether in big pieces or in little ones; but sometimes it is passed
+over screens, and in this process the dust and smaller bits drop out.
+
+The second kind of coal, the sort that is hard and bright, is
+anthracite. Its name is connected with a Greek word meaning ruby. It
+burns with a glow, but does not blaze. Most of the anthracite coal is
+used in houses, and householders will not buy it unless the pieces are
+of nearly the same size and free from dirt, coal dust, and slate. The
+work of preparation is done in odd-shaped buildings called "breakers."
+One part of a breaker is often a hundred or a hundred and fifty feet
+in height. The coal is carried to the top of the breaker. From there
+it makes a journey to the ground, but something happens to it every
+little way. It goes between rollers, which crush it; then over
+screens, through which the smaller pieces fall. Sometimes the screens
+are so made that the coal will pass over them, while the thin, flat
+pieces of slate will fall through. In spite of all this, bits of coal
+mixed with slate sometimes slide down with the coal, and these are
+picked out by boys. A better way of getting rid of them is now coming
+into use. This is to put the coal and slate into moving water. The
+slate is heavier than the coal, and sinks; and so the coal can easily
+be separated from it. Dealers have names for the various sizes of
+coal. "Egg" must be between two and two and five eighths inches in
+diameter; "nut" between three fourths and one and one eighth inches;
+"pea" between one half and three fourths of an inch.
+
+Mining coal is dangerous work. Any blow of the pickaxe may break into
+a vein of water which will burst out and flood the mine. The wooden
+props which support the roof may break, or the pillars of coal may not
+be large enough; and the roof may fall in and crush the workers. There
+are always poisonous gases. The coal, as has been said before, was
+made under water, and therefore the gas which was formed in the
+decaying leaves and wood could not escape. It is always bubbling out
+from the coal, and at any moment a pickaxe may break into a hole that
+is full of it. One kind of gas is called "choke-damp," because it
+chokes or suffocates any one who breathes it. There is also
+"white-damp," the gas which you see burning with a pretty blue flame
+over a hot coal fire. Worst of all is the "fire-damp." If you stir up
+the water in a marsh, you will see bubbles of it rise to the surface.
+It is harmless in a marsh, but quite the opposite in a mine. When it
+unites with a certain amount of air, it becomes explosive, and the
+least bit of flame will cause a terrible explosion. Even coal dust may
+explode if the air is full of it, and it is suddenly set in motion by
+too heavy a blast of powder.
+
+Miners used to work by candlelight. Every one knew how dangerous this
+was; but no one found any better way until, about a hundred years ago,
+Sir Humphry Davy noticed something which other people had not
+observed. He discovered that flame would not pass through fine wire
+gauze, and he made a safety lamp in which a little oil lamp was placed
+in a round funnel of wire gauze. The light, but not the flame, would
+pass through it; and all safety lamps that burn oil have been made on
+this principle. The electric lamp, however, is now in general use. The
+miner wears it on his cap, and between his shoulders he carries a
+small, light storage battery. Even with safety lamps, however, there
+are sometimes explosions. The only way to make a mine at all safe from
+dangerous gases is to keep it full of fresh, pure air. There is no
+wind to blow through the chambers and passages, and therefore air has
+to be forced in. One way is to keep a large fire at the bottom of the
+air shaft. If you stand on a stepladder, you will feel that the top of
+the room is much warmer than the floor. This is because hot air
+rises; and in a mine, the hot air over the fire rises and sucks the
+foul air and gas out of the mine, and fresh air rushes in to take its
+place. Another way is by a "fan," a machine that forces fresh air into
+the mine.
+
+[Illustration: MINERS AND THEIR MINE
+
+Notice the safety lamps in the men's caps, and the little railroad on
+which the cars of coal and ore travel, hauled by the useful mule.]
+
+So it is that by hard work and much danger we get coal for burning.
+Now, coal is dirty and heavy. A coal fire is hard to kindle and hard
+to put out, and the ashes are decidedly disagreeable to handle. And
+after all, we do not really burn the coal itself, but only the gas
+from it which results from the union of carbon and oxygen. In some
+places natural gas, as it is called, which comes directly from some
+storehouse in the ground, is used in stoves and furnaces and
+fireplaces for both heating and cooking; and perhaps before long gas
+will be manufactured so cheaply and can be used so safely and
+comfortably that we shall not have to burn coal at all, but can use
+gas for all purposes--unless electricity should take its place.
+
+
+
+
+II
+
+DOWN IN THE QUARRIES
+
+
+When walking in the country one day I came to a beautiful pond by the
+side of the road. The water was almost as clear as air, and as I
+looked down into it, I could see that the bottom was made of granite.
+The farther shores were cliffs of clean granite thirty or forty feet
+high and coming down to the water's edge. The marks of tools could be
+seen on them, showing where blocks of stone had evidently been split
+off. I picked up a piece of the rock and examined it closely. It
+proved to be made up of three kinds of material. First, there were
+tiny sparkling bits of mica. In some places there are mica mines
+yielding big sheets of this curious mineral which is used in the doors
+of stoves and the little windows of automobile curtains. With the
+point of a knife the bits in my piece of granite could be split into
+tiny sheets as thin as paper. The second material was quartz. This was
+grayish-white and looked somewhat like glass. The third material was
+feldspar. This, too, was whitish, but one or two sides of each bit
+were flat, as if they had not been broken, but split. This is the most
+common kind of granite. There are many varieties. Some of them are
+almost white, some dark gray, others pale pink, and yet others deep
+red. It is found in more than half the States of the Union.
+
+This quarry had been given up and allowed to fill with water; but it
+was a granite country, and farther down the road there was another,
+where scores of men were hard at work. This second quarry was part-way
+up a hill; or rather, it was a hill of granite which men were digging
+out and carrying away. When they began to open the quarry, much of the
+rock was covered with dirt and loose stones, and even the granite that
+showed aboveground was worn and broken and stained. This is called
+"trap rock." The easiest way to get rid of it is to blast with
+dynamite and then carry away the dirt and fragments. Next comes the
+getting out of great masses of rock to use, some of them perhaps long
+enough to make the pillars of a large building.
+
+[Illustration: OPENING A GRANITE QUARRY
+
+_Courtesy Jones Brothers Company._
+
+The first thing to do is to strip off the soil from the stone. Then,
+as the blocks are cut out, the big derrick lifts and loads them on
+waiting cars.]
+
+Now, granite is a hard stone, but there is no special difficulty in
+cutting it if you know how. In the old days, when people wished to
+split a big boulder, they sometimes built a fire beside it, and when
+it was well heated, they dropped a heavy iron ball upon it. King's
+Chapel in Boston was built of stone broken in this way. To break from
+a cliff, however, a block of granite big enough to make a long pillar
+is a different matter, and this is what the men were doing. First of
+all, the foreman had examined the quarry till he had found a stratum
+of the right thickness. He had marked where the ends were to come, and
+the men had drilled holes down to the bottom of the stratum. Then he
+had drawn a line at the back along where he wished the split to be,
+and the men had drilled on this line also a row of holes. Next came
+the blasting. If one very heavy charge had been exploded, it would
+probably have shattered the whole mass, or at any rate have injured it
+badly. Instead of this, they put into each hole a light charge of
+coarse powder and covered it with sand. These were all fired at the
+same instant, and thus the great block was loosened from the wall.
+Sometimes there seems to be no sign of strata, and then a line of
+horizontal holes must be drilled where the bottom of the block is to
+be. After this comes what is called the "plug-and-feather" process.
+Into each hole are placed two pieces of iron, shaped like a pencil
+split down the middle. These are the "feathers." The "plug" is a small
+steel wedge that is put between the iron pieces. Then two men with
+hammers go down the line and strike each wedge almost as gently as if
+it was a nut whose kernel they were afraid of crushing. They go down
+the line again, striking as softly as before. Then, if you look
+closely, you can see a tiny crack between the holes. There is more
+hammering, the crack stretches farther, a few of the wedges are driven
+deeper and the others drop out. The block splits off. A mighty chain
+is then wound about it, the steam derrick lifts it, lays it gently
+upon a car, and it is carried to the shed to be cut into shape,
+smoothed, and perhaps polished.
+
+In almost every kind of work new methods are invented after a while.
+In quarrying, however, the same old methods are in use. The only
+difference is that, instead of the work being done by muscle, it is
+done by compressed air or steam or electricity. Compressed air or
+steam works the drill and the sledgehammer. The drill is held by an
+arm, but the arm is a long steel rod which is only guided by the
+workman. Not the horse-sweep of old times, but the steam derrick and
+the electric hoist lift the heavy blocks from the quarry. Polishing
+used to be a very slow, expensive operation, because it was all done
+by the strength of some one's right arm, but now, although it takes as
+much work as ever, this work is done by machinery. To "point" a piece
+of stone, or give it a somewhat smooth surface, is done now with tools
+worked by compressed air. After this, the stone is rubbed--by
+machinery, of course--with water and emery, then by wet felt covered
+with pumice or polishing putty. A few years ago two young Vermonters
+invented a machine that would saw granite. This saw has no teeth, but
+only blades of iron. Between these blades and the piece of granite,
+however, shot of chilled steel are poured; and they do the real
+cutting.
+
+Granite has long been used in building wherever a strong, solid
+material was needed; but until the sand blast was tried, people
+thought it impossible to do fine work in this stone. There was a firm
+in Vermont, however, who believed in the sand blast. They had a
+contract with the Government to furnish several thousand headstones
+for national cemeteries. Cutting the names would be slow and costly;
+so they made letters and figures of iron, stuck them to the stones,
+and turned on the blast. If a sand blast is only fast enough, it will
+cut stone harder than itself. The blast was turned upon a stone for
+five minutes. Then the iron letters were removed. There stood in
+raised letters the name, company, regiment, and rank of the soldier,
+while a quarter of an inch of the rest of the stone, which the iron
+letters had not protected, had been cut away. By means of the sand
+blast it has become possible to do beautiful carving even in material
+as hard as granite.
+
+Granite looks so solid that people used to think it was fireproof; but
+it is really poor material in a great fire. Most substances expand
+when they are heated; but the three substances of which granite is
+made do not expand alike, and so they tend to break apart and the
+granite crumbles.
+
+A marble quarry is even more interesting than a granite quarry. If you
+stand on a hill in a part of the country where marble is worked, you
+will see white ledges cropping out here and there. The little villages
+are white because many of the houses are built of marble. Then, too,
+there are great marble quarries flashing in the sunshine. Sometimes a
+marble quarry is chiefly on the surface. Sometimes the marble
+stretches into the earth, and the cutting follows it until a great
+cavern is made, perhaps two or three hundred feet deep. A roof is
+often built to keep out the rain and snow. It keeps out the light,
+too, and on rainy days the roof, together with the smoke and steam of
+the engines, makes the bottom of the quarry a gloomy place. Everywhere
+there are slender ladders with men running up and down them. There
+are shouts of the men, clanking of chains, and puffing of locomotives.
+
+Marble is cut out in somewhat the same way as granite, but a valuable
+machine called a "channeler" is much used. This machine runs back and
+forth, cutting a channel two inches wide along the ends and back and
+sometimes the bottom of the block to be taken out.
+
+Marble is so much softer than granite that it is far more easy to
+work. Cutting it is a simple matter. The saw, which is a smooth flat
+blade of iron, swings back and forth, while between it and the marble
+sand and water are fed. It does not exactly _cut_, but rubs, its way
+through. The round holes in the tops of washstands are cut by saws
+like this, only bent in the form of a cylinder and turned round and
+round, going in a little deeper at each revolution. A queer sort of
+saw is coming into use. It is a cord made of three steel wires twisted
+loosely together. This cord is stretched tightly over pulleys and
+moves very rapidly. Every little ridge of the cord strikes the stone
+and cuts a little of it away.
+
+There are varieties of marble without end. The purest and daintiest is
+the white of which statues are carved; but there are black, red,
+yellow, gray, blue, green, pink, and orange in all shades. Many are
+beautifully marked. The inner walls of buildings are sometimes covered
+with thin slabs of marble. These are often carefully split, and the
+two pieces put up side by side, so that the pattern on one is reversed
+on the other. Certain kinds of marble contain fossils or remains of
+coral and other animals that lived hundreds of thousands of years ago.
+In some marbles there are so many that the stone seems to be almost
+made of them. When a slab is cut and polished, the fossils are of
+course cut into; but even then we can sometimes see their shape. One
+of the most common is the crinoid. This was really an animal, but it
+looked somewhat like a closed pond lily with a long stem, and people
+used to call it the stone lily. This stem is made up of little flat
+rings looking like bits of a pipestem. The stems are often broken up
+and these bits are scattered through the marble. The animals whose
+shells help to make marble lived in the ocean, and when they died sank
+to the bottom. Many of the shells were broken by the beating of the
+waves, but both broken shells and whole ones became united and
+hardened into limestone, one kind of which we call marble. Common
+chalk is another kind. Blackboard crayons are made of this: so are
+whitewash and whiting for cleaning silver and making putty.
+
+Another stone that builders would be sorry to do without is slate.
+This, too, was formed at the bottom of the sea. Rivers brought down
+fine particles of clay, which settled, were covered by other matter,
+and finally became stone. It was formed in layers, of course, but,
+queerly enough, it splits at right angles to its bottom line. Just why
+it does this is not quite certain, but the action is thought to be due
+to heat and long, slow pressure, which will do wonderful things, as in
+the case of coal. This splitting is a great convenience for the
+people who want to use it for roofing and for blackboards. Blocks of
+slate are loosened by blasting, and are taken to the splitting-shed.
+
+Splitting slate needs care, and a man who is not careful should never
+try to work in a slate quarry. The splitting begins by one man's
+dividing the block into pieces about two inches thick and somewhat
+larger than the slates are to be when finished. The way he does this
+is to cut a little notch in one end of the block with his "sculpin
+chisel" and make a groove from this across the block. He must then set
+his chisel into the groove, strike it with a mallet, and split the
+slate to the bottom. This sounds easy, but it needs skill. Slate has
+sometimes its own notions of behavior, and it does not always care to
+split in a straight line exactly perpendicular to the bottom of the
+stratum. The man keeps it wet so that he can see the crack more
+plainly, and if that crack turns back a little to the right, he must
+turn it to the left by striking the sculpin toward the left, or
+perhaps by striking a rather heavy blow on the left of the stone
+itself. Now the chief splitter takes it, and with a broad thin chisel
+he splits it into plates becoming thinner at each split. The second
+assistant trims these into the proper shape and size with either a
+heavy knife or a machine. Slate can be sawed and planed; but whatever
+is done to it should be done when it first comes from the quarry, for
+then it is not so likely to break. It would be very much cheaper if so
+much was not broken and wasted at the quarries and in the splitting.
+It is said that in Wales sometimes one hundred tons of stone are
+broken up to get between three and four tons of good slate. Within the
+last few years the quarrymen have been using channeling machines and
+getting out the slate in great masses instead of small blocks. This is
+not so wasteful by any means; but even now there is room for new and
+helpful inventions.
+
+
+
+
+III
+
+HOUSES OF SAND
+
+
+If you wanted to build a house, of what should you build it? In a new
+country, people generally use wood; but after a time wood grows
+expensive. Moreover, wood catches fire easily; therefore, as a country
+becomes more thickly settled and people live close together in cities,
+stone and brick are used. Large cities do not allow the building of
+wooden houses within a certain distance from the center, and sometimes
+even the use of wooden shingles is forbidden. Of late years large
+numbers of "concrete" or "cement" houses have been built. Our
+grandfathers would have opened their eyes wide at the suggestion of a
+house built of sand, and would have felt anxious at every rainfall
+lest their homes should suddenly melt away. Even after thousands of
+concrete buildings were in use, many people still feared that they
+would not stand the cold winters and hot summers of the United States;
+but it has been proved that concrete is a success provided it is
+properly made.
+
+No one can succeed in any work unless he understands how it should be
+done. Concrete is made of Portland cement, mixed with sand and water
+and either broken stone, gravel, cinders, or slag; but if any one
+thinks that he can mix these together without knowing how and produce
+good concrete, he will make a bad mistake rather than a good building
+material.
+
+First, he must buy Portland cement of the best quality. This cement is
+made of limestone and clay, or marl, chalk, and slag. These are
+crushed and ground and put into a kiln which is heated up to 2500° or
+3000°F.; that is, from twelve to fourteen times as hot as boiling
+water. The stone fuses sufficiently to form a sort of clinker. After
+this has cooled, it is ground so fine that the greater part of it will
+pass through a sieve having 40,000 meshes to the square inch. To every
+hundred pounds of this powder, about three pounds of gypsum is added.
+The mixture is then put into the bags in which we see it for sale in
+the stores. This powder is so greedy for water that it will absorb the
+moisture from the air around it. Even in the bags, it begins to harden
+as soon as it gets some moisture; and as soon as it hardens, it is of
+no use. The moral of that is to keep your cement in a dry place.
+
+The second substance needed in concrete is broken stone or gravel. Of
+course a hard rock must be selected, such as granite or trap rock.
+Limestone calcines in a heat exceeding 1000° F., and therefore it
+cannot be used in fireproof construction. Soft rock, like slate or
+shale or soft sandstone, will not answer because it is not strong
+enough. Gravel is always hard. If you look at a cut in a gravel bank,
+you will usually see strata of sand and then strata of rounded pebbles
+of different sizes. The sand was once an ancient sea beach; the
+pebbles were dashed up on it by waves or storms or some change of
+currents. They were at first only broken bits of rock, but after being
+rolled about for a few thousand years in the ocean and on the shore,
+the corners were all rounded. Soft rock would have been ground to
+powder by such treatment. Sometimes, if there is to be no great strain
+on the concrete, cinders or pieces of brick may be used instead of
+stone; and for some purposes they answer very well.
+
+The third substance used in concrete is sand; but it must be the right
+kind of sand, having both fine and coarse grains. These grains need to
+be sharp, or the cement will not stick to them well. They must also be
+clean, that is, free from dirt. If you rub sand between your hands,
+and it soils them, then there is clay or loam with it, and it must not
+be used in making concrete unless it is thoroughly washed. Another way
+of testing it is to put it into a glass jar partly full of water and
+shake it. Then let it settle. If there is soil in the sand, it will
+appear as a stratum of mud on top of the sand.
+
+The water with which these three substances are to be mixed must be
+clean and must contain no acid and no strong alkali. As a general
+rule, there must be twice as much broken stone as sand. When people
+first make concrete, they often expect too much of their materials. A
+good rule for the strongest sort of cement, strong enough for floors
+on which heavy machines are to stand, is one fourth of a barrel of
+cement, half a barrel of sand, and one barrel of gravel or broken
+stone. Apparently this would make one and three fourths barrels; but
+in reality it makes only about one barrel, because the sand fills in
+the spaces between the gravel, and the cement fills in the spaces
+between the grains of sand.
+
+There are many sorts of machines on the market for mixing the
+materials; but small quantities can just as well be mixed by hand. The
+"mixing-bowl" is a platform, and on this the sand is laid. Then comes
+the cement; and these two must be shoveled together several times.
+While this is being done, the broken stone or gravel must be wet, and
+now it is put on top of the sand and cement and well shoveled
+together, with just enough water added so that the mass will almost
+bear the weight of a man.
+
+Concrete is impatient to be hardening, and if it is not put into the
+right place, it will begin promptly to harden in the wrong place, and
+nothing can be done with it afterwards. If it is to be made in blocks,
+the moulds must be ready and the concrete put into them at once and
+well tamped down. For such uses as beams and the sides of tanks where
+great strength is needed, the cement is often "reinforced," that is,
+rods of iron or steel are embedded in it. For floors, a sheet of woven
+wire is often stretched out and embedded. At first only solid blocks,
+made to imitate rough stone, were used for houses, but the hollow
+block soon took their place. This is cheaper; houses built this way
+are warmer in winter and cooler in summer; and it prevents moisture
+from working through the walls. Many cities have regulations about the
+use of hollow blocks, all the more strict because concrete is
+comparatively new as a building material. In Philadelphia the blocks
+must be composed of at least one barrel of Portland cement to five
+barrels of crushed rock or gravel. They must be three weeks old or
+more before being used; the lintels and sills of the doors must be
+reinforced; and every block must be marked, so that if the building
+should not prove to be of proper strength, the maker may be known.
+There would seem, however, to be little question of the quality of the
+blocks, for samples must pass the tests of the Bureau of Building
+Inspection.
+
+Even better than the hollow block is the method of making the four
+walls of a house at once by building double walls of boards and
+pouring in the concrete. When this has hardened, the boards are
+removed, and whatever sort of finish the owner prefers is given to the
+walls. They can be treated by spatter-work, pebble dash, or in other
+ways before the cement is fully set, or by bush hammering and tool
+work after the cement has hardened. Coloring matter can be mixed with
+the cement in the first place; and if the owner decides to change the
+color after the house is completed, he can paint it with a thin cement
+of coloring matter mixed with plaster of Paris.
+
+A concrete house has several advantages. In the first place, it will
+not burn. Neither will granite, but granite will fall to pieces in a
+hot fire. Granite is made of quartz, mica, and feldspar, as has been
+said before. These three do not expand alike in heat; and therefore
+great flakes of the stone split off, so that it really seems to melt
+away. A well-made concrete is not affected by fire. It will not burn,
+and it will not carry heat to make other things burn. For a concrete
+house no paint is needed and less fuel will be required to keep it
+warm. If the floors are made with even a very little slant,
+"house-cleaning" consists of removing the furniture and turning on the
+hose. Water-tank, sink, washtubs, and bathtubs can be cast in concrete
+and given a smooth finish. Wooden floors can be laid over the
+concrete, or a border of wood can be put around each room for tacking
+down carpets or rugs. A concrete house may be as ornamental as the
+owner chooses, for columns and cornices and mouldings can easily be
+made of concrete; and if they are cast in sand, as iron is, they will
+have a finish like sandstone.
+
+It is somewhat troublesome to lay concrete in very cold weather,
+because of the danger of freezing and cracking. Sometimes the
+materials are heated, and after the concrete is in place, straw or
+sand or sawdust is spread over it. These will keep it warm for several
+hours, and so give the concrete a chance to "set." Sometimes a canvas
+house is built over the work. When a concrete dam was to be built in
+the Province of Quebec and the mercury was 20° below zero, the
+contractors built a canvas house over one portion of the dam and set
+up iron stoves in it. When this part was completed, they took down the
+house and built it up again over another portion of the dam.
+Sometimes salt is used. Salt water is heavier than fresh water and
+will not freeze so easily. Therefore salt put into the water used in
+making the concrete will enable it to endure more cold without
+freezing; but not more than one pound of salt to twelve gallons of
+water should be used.
+
+[Illustration: BUILDING A CONCRETE ROAD
+
+_Courtesy Alpha Portland Cement Co._
+
+The concrete mixer travels along the prepared roadbed, and after it
+follow the workmen with levelers and stamps.]
+
+Concrete objects to being frozen before it is "set," but it is
+exceedingly accommodating about working under water. It must, of
+course, be carried in some way through the water to its proper place
+without being washed away, but this is easily done. Sometimes it is
+let down in great buckets closed at the top, but with a hinged bottom
+that will open when the bucket strikes the rock or soil where the
+material is to be left. Sometimes it is poured down through a tube.
+Sometimes it is dropped in sacks made of cloth. This cloth must be
+coarse, so that enough of the concrete will ooze through it to unite
+the bag and its contents with what is below it and make a solid mass.
+Sometimes even paper bags have been successfully used. The concrete,
+made rather dry, is poured into the bags and they are slid down a
+chute. The paper soon becomes soft and breaks, and lets the concrete
+out. Sometimes concrete blocks are moulded on land and lowered by a
+derrick, while a diver stands ready to see that they go into their
+proper places.
+
+Concrete is used for houses, churches, factories, walls, sidewalks,
+steps, foundations, sewers, chimneys, piers, cellar bottoms, cisterns,
+tunnels, and even bridges. In the country, it is used for silos, barn
+floors, ice houses, bins for vegetables, box stalls for horses,
+doghouses, henhouses, fence posts, and drinking-troughs. It is of very
+great value in filling cavities in decaying trees. All the decayed
+wood must be cut out, and some long nails driven from within the
+cavity part-way toward the outside, so as to help hold the concrete.
+Then it is poured in and allowed to harden. If the cavity is so large
+that there is danger of the trunk's breaking, an iron pipe may be set
+in to strengthen it. If this is encased in concrete, it will not rust.
+A horizontal limb with a large cavity may be strengthened by bending a
+piece of piping and running one part of it into the limb and the other
+into the trunk, then filling the whole cavity with concrete. If the
+bark is trimmed in such a way as to slant in toward the cavity, it
+will sometimes grow entirely over it.
+
+Concrete is also used for stucco work, that is, for plastering the
+outside of buildings. If the building to be stuccoed is of brick or
+stone, the only preparation needed is to clean it and wet it; then put
+on the plaster between one and two inches thick. A wooden house must
+first be covered with two thicknesses of roofing-paper, then by wire
+lathing. The concrete will squeeze through the lathing and set. Stucco
+work is nothing new, and if it is well done, it is lasting.
+
+Concrete has been used for many purposes besides building, and the
+number of purposes increases rapidly. For blackboards, refrigerator
+linings, and railroad ties it has been found available, and for poles
+or posts of all sizes it has already proved itself a success. It has
+even been suggested as an excellent material for boats, if reinforced;
+and minute directions are given by one writer for making a concrete
+rowboat. To do this, the wooden boat to be copied is hung up just
+above the ground, and clay built around it, leaving a space between
+boat and clay as thick as the concrete boat is to be. The wooden boat
+is covered with paper and greased, then the concrete is poured into
+the space between the boat and the clay mould; and when it hardens and
+the wooden boat is removed, there is a boat of stone--or so the
+directions declare; but I think most people would prefer one of wood.
+However it may be with rowboats, concrete is taking an important place
+in the construction of battleships, a backing for armor being made of
+it instead of teakwood. The Arizona is built in this way.
+
+Concrete that is carelessly made is very poor stuff, and dangerous to
+use, for it is not at all reliable and may give out at any time; but
+concrete that is made of the best materials and properly put together
+is an exceedingly valuable article.
+
+
+
+
+IV
+
+BRICKS, THEIR FAULTS AND THEIR VIRTUES
+
+
+The simplest way to make a brick is to fill a mould with soft clay,
+then take it out and let it stiffen, and then put it in the sun to
+dry. This is the way in which the "adobe" bricks of Central America
+are made. They answer very well in countries where there is little
+rain; but one or two heavy downpours would be likely to melt a house
+built of such material.
+
+Clay is a kind of earth containing mostly alumina and silica or sand,
+that can be mixed with water, moulded into any shape, retain that
+shape after it is dry, and become hard by being burned. If you want to
+make a china cup, you must have a fine sort of clay called "kaolin,"
+which is pure white when it is fired and is not very common; but if
+you want to make bricks, it will not be at all difficult to find a
+suitable clay bank. And yet the clay, even for bricks, must be of the
+right kind. If it contains too much silica (sand), the brick will not
+mould well; if too much alumina it will be weak; if too much iron, it
+will lose its shape in burning; if too much lime, it will be
+flesh-colored when it is burned.
+
+If you want to find out whether a building-brick is of good quality,
+there are some tests that a boy or girl can apply as well as any one.
+First, look the brick over and note whether it is straight and true,
+and whether the edges and corners are sharp. Strike it, and see
+whether it gives a clear, ringing sound. Then weigh it and soak it in
+water for twenty-four hours. Weigh it again, and if it is more than
+one fifth heavier than it was before soaking, it is not of the first
+quality.
+
+After the clay has been dug, it must be "tempered," that is, mixed
+with water and about one third or one fourth as much sand as clay, and
+left overnight in a "soak pit," a square pit about five feet deep. In
+the morning the workmen shovel the mass over and feed it into the
+machines for forming the bricks. The mixing is better done, however,
+in a "ring pit." This is a circular pit twenty-five or thirty feet in
+diameter, three feet deep, and lined with boards or brick. A big iron
+wheel works from the center to the edge and back again for several
+hours, through and through the clay. A method even better than this is
+to put the clay and sand and water into a great trough, in which there
+is a long shaft bristling with knives. The shaft revolves, mixes the
+clay, and pushes it along to the end of the trough. This is called
+"pugging," and the whole thing--trough, shaft, and knives--is a "pug
+mill."
+
+In the old days bricks were always made by hand. The moulder stood in
+front of a wet table whereon lay a heap of soft clay. He either wet or
+sanded his mould to keep it from sticking. Meanwhile, his assistant
+had cut a piece of clay and rolled it and patted it into the shape of
+the mould. In making bricks, there can be no patching; the mould
+must be filled at one stroke, or else there will be folds in the
+brick. To make a good brick, the moulder lifts the clay up above his
+head and throws it into the mould with all his force. Then he presses
+it into the corners with his thumbs, scrapes off with a strip of wood
+any extra clay, or cuts it off with a wire, smooths the surface of the
+brick, puts mould and brick upon a board, jerks the mould up and
+proceeds to make another brick.
+
+[Illustration: IN A NEW JERSEY BRICK MILL
+
+_Copyright by Underwood and Underwood._
+
+This man is moulding a fire-brick to its final shape.]
+
+No matter how expert a moulder may be, brick-making by hand is slow
+work, and in most places machines are used. In what is called the
+"soft-mud" process, the clay is pushed on by the pug mill to the end
+of the trough. There stands a mould for six bricks. A plunger forces
+the clay into it, the mould is emptied, and in a single hour five
+thousand bricks can be made. By what is called the "stiff-mud"
+process, the stiff clay is put into a machine with an opening the size
+of the end or side of a brick. The machine forces the clay through
+this opening, cuts it off at the proper moment; and so makes bricks by
+the thousand without either mould or moulder. A third way of making
+brick is by what is called the "dry process." The clay is pulverized
+and filled into moulds the length and breadth of a brick, but much
+deeper, and with neither top nor bottom. One plunger from above and
+another from below strike the clay in the mould with much force, and
+make the fine, smooth brick known as "pressed brick." All this is done
+by machinery, and some machines make six bricks at a time. These
+"dry" bricks are fragile before they are burned, and must be handled
+with great care.
+
+Bricks cannot be put into the kiln while they are still wet, for when
+a brick is drying, it is a delicate article. It objects to being too
+hot or too cold, and it will not stand showers or drafts. In some way
+about a pound of water must be dried out of each brick; but if you try
+to hurry the drying, the brick turns sulky, refuses to have anything
+more to do with you, and proceeds to crack. To dry, bricks are
+sometimes spread on floors; or piled up in racks on short pieces of
+board called "pallets"; and sometimes they are put upon little cars
+and run slowly through heated tunnels. The last is the best way for
+people who are in a hurry, for it takes only from twenty-four to
+thirty-six hours to make the bricks ready to go to the kiln to be
+burned.
+
+In one sort of kiln, the bricks themselves make the kiln. They are
+piled up in arches, but left a little way apart so the hot air can
+move freely among them. The sides of the structure are covered with
+burnt brick and mud, but the top is left open to allow the steam from
+the hot bricks to escape. The fires are in flues that are left at the
+bottom. They must burn slowly at first, but after a while, some forty
+to sixty hours, the heat becomes intense. Thus far the bricks have
+been grayish or cream-colored, but now, if there is iron in them, they
+turn red; if there is lime, they turn yellow; if a large amount of
+lime, they become flesh-colored. Besides this sort of kiln, which is
+torn down when the bricks are sufficiently burned, there is also the
+permanent kiln, which has fixed side walls and either an open or
+closed top. Then, too, there is a "continuous" kiln. This has a number
+of chambers, and the heat from each one passes into the next; so that
+bricks in one chamber may be just warming up while in another they are
+ready to be taken out.
+
+When the bricks come out of the kiln, some of them are good and some
+are not. Those that were on the outside are not burned enough; those
+next it are not well baked, but can be used for the middle of thick
+walls. The next ones are of good quality; but those directly over the
+fires are so hard and brittle that they are of little use except for
+pavements.
+
+Paving-bricks, however, are not to be despised. They are not as smooth
+and well finished as pressed brick, but they are exceedingly useful.
+They need as much care in making as any others, and they must be
+burned in a much hotter fire to make them dense and hard. The tests
+for paving-bricks are quite different from those for ordinary
+building-brick. If first-class paving-bricks weighing fifty pounds are
+soaked in water for twenty hours, they take up so little water that
+they will not weigh more than fifty-one or fifty-one and a half pounds
+when taken out. To find out how hard they are, the bricks are weighed
+and shaken about with foundry shot for a number of hours. Then they
+are weighed again to see how much of their material has been rubbed
+off. A third test is to put one brick on edge into a crushing machine
+to see how much pressure it will stand. Paving-brick is cheaper than
+granite blocks, and if it has a good foundation of concrete covered
+with sand, it will last about three fourths as long. Brick is less
+noisy than stone and is easier to clean.
+
+Not so very long ago, when particularly handsome bricks were needed
+for the outside of walls and other places where they would be
+conspicuous, they were "re-pressed"; that is, they were made by hand
+or in a "soft-mud" machine, and then, after drying for a while, were
+put into a re-pressing machine to give them a smooth finish. These
+machines are still used, but they are hardly necessary, for the
+"dry-clay" brick machine will turn out a smooth brick in one
+operation.
+
+Another substance which is made of almost the same materials as brick
+is terra cotta. To make this, fire brick, bits of pottery, partly
+burned clay, and fine white sand are ground to a powder and mixed very
+thoroughly. This mixture is moulded, dried, and burned. Until
+recently, all terra cotta was of the color that is called by that
+name, but now it is made in gray, white, and bronze as well.
+
+Bricks are laid in mortar, and this makes a wall one solid mass and
+stronger than it could be without any cement. But mortar does more
+than this. It is more elastic than brick, and therefore, when a wall
+settles, the mortar yields a little, and this often prevents the
+bricks from cracking. Bricks are always thirsty, and if one is laid in
+mortar, it will suck the moisture out of it almost as a sponge will
+suck up water. The mortar thus has no chance to set, and so is not
+strong as it should be. That is why the bricklayer wets his bricks,
+especially in summer, before he puts them in place. Lime or cement
+mortar will not set in freezing weather, and a brick building put up
+in the winter is in danger of tumbling down when the warm days of
+spring arrive.
+
+This thirstiness of bricks is their greatest fault. Three or four days
+of driving rain will sometimes wet through a brick wall two feet
+thick, crumbling the plaster and spoiling the wallpaper. That is why
+it is a poor plan to plaster directly on the brick wall of a house.
+"Furring" strips, as they are called, or narrow strips of wood, should
+be fastened on first and the laths nailed to these, or the wall can be
+painted or oiled on the outside. The best way, however, though more
+expensive, is to build the wall double. Then there is air between the
+two thicknesses of brick. Air is a poor conductor of heat; so in
+summer it keeps the heat out, and in winter it keeps it in.
+
+But brick will suck up water from the ground as well as from a storm;
+and therefore, when a brick house is to be built in a wet place, there
+ought to be a three-eighths-inch layer of something waterproof, like
+asphalt and coal tar, put on top of one of the layers of brickwork to
+prevent the moisture from creeping up.
+
+Bricks have their faults, but they will not burn, and when properly
+used, they make a most comfortable and enduring house.
+
+
+
+
+V
+
+AT THE GOLD DIGGINGS
+
+
+When gold was first discovered in California, in 1848, people from all
+over the world made a frantic rush to get there, every one of them
+hoping that he would be lucky enough to make his fortune, and fearing
+lest the precious metal should be gone before he could even begin to
+dig. The gold that these men gathered came from what were called
+"placers"; that is, masses of gravel and sand along the beds of
+mountain streams. Each miner had a pan of tin or iron, which he filled
+half-full of the gravel, or "pay dirt," as the miners called it. Then,
+holding it under water, he shook off the stones and mud over the side
+of the pan, leaving grains of gold mixed with black sand at the
+bottom. This black sand was iron, and after a while the miners removed
+it with a magnet, dried what remained, and blew away the dust, leaving
+only the grains of gold.
+
+Another contrivance which soon came into use was the "cradle." This
+was a long box, sometimes only a hollowed-out log. At the top was a
+sieve which sifted out the stones. Nailed to the bottom of the cradle
+were small cleats of wood, or "riffles," which kept the water from
+running so fast as to sweep the gold out of the cradle with it. The
+cradle was placed on rockers and was also tilted slightly. The miner
+shoveled the gravel into the top of the cradle and his partner rocked
+it. The sieve kept back the stones, the water broke up the lumps of
+earth and gravel and washed them down the cradle, and the grains of
+gold were stopped by the riffles, and sank to the bottom. Sometimes
+the "pay dirt" continued under a stream. To get at it, the miners
+often built a little canal and turned the water into a new channel;
+then they could work on the former bed of the river.
+
+Before many years had passed, the gold that was near the surface had
+been gathered. The miners then followed the streams up into the
+mountains, and found that much of the gold had come from beds where in
+ancient times rivers had flowed. There was gold still remaining in
+these beds, but it was poorly distributed, the miners thought.
+Sometimes there would be quite an amount in one place, and then the
+miner would dig for days without finding any more. Even worse than
+this was the fact that these gravel beds were not on the top of the
+ground, but were covered up with soil and trees. Evidently the slow
+work with pans and cradles would not pay here; but it occurred to some
+one that if a powerful stream of water could be directed against the
+great banks of earth, as water is directed against a burning building,
+they would crumble, the dirt could be washed down sluices, and the
+gold be saved. This was done. Great reservoirs were built high up in
+the mountains, and water was brought by means of ditches or pipes to a
+convenient place. Then it was allowed to rush furiously through a
+hose and nozzle, and the great stream coming with tremendous force was
+played upon the banks of gravel. The banks crumbled, the gravel was
+washed into a string of sluices, or long boxes with riffles to catch
+the gold. Soon the miners found that if quicksilver was put into these
+sluices, it would unite with the gold and make a sort of paste called
+"amalgam." Then if this amalgam was heated, the quicksilver would be
+driven off in the form of gas, and the gold would remain in a
+beautiful yellow mass.
+
+[Illustration: HYDRAULIC GOLD MINING
+
+A placer mine at Gold Point, California, where tremendous streams of
+water under high pressure are busy washing away the side of a
+gold-bearing hill.]
+
+The ancient rivers had also carried gold to the valleys, and to
+collect this a dredge, which the miners called a "gold ship," came
+into use. The "ship" part of this machine is an immense flat scow.
+Stretching out from one end is something which looks like a moving
+ladder. This is the support of an endless chain of buckets, each of
+which can bite into the gravel and take a mouthful of five or six
+hundred pounds. They drop this gravel into a big drum which is
+continually revolving. Water flows through the drum, and washes out
+the sand and bits of gold over large tables, where by means of riffles
+and quicksilver the gold is captured. This scow was usually on dry
+land at first; but its digging soon made a lake, and then it floated.
+It must be more fascinating to hold a pan in your own hands and pick
+out little grains of gold or perhaps even a big piece of it with your
+own fingers, but if the gravel is good the dredge makes more money.
+
+In Alaska the great difficulty in mining is that, except at the
+surface, the ground is frozen all the year round. At first, the miners
+used to thaw the place where they wished to dig by building wood
+fires; but this was a slow method, and now the thawing is done by
+steam. They carry the steam in a pipe to the place where the digging
+is to be done, and send it through a hose. At the end of the hose is a
+pointed steel tube. They hammer this tube into the ground and let some
+steam pass through the nozzle. This softens the ground so that picks
+and shovels may be used. There is generally cold enough in Alaska, but
+once at least the miners had to manufacture it. The gold-bearing
+gravel was deep, the ground was flat, and it was often overflowed.
+They set up a freezing plant, and shut in their land with a bulkhead
+of ice several feet thick. Then they pumped out what water was already
+in and did their work with no more trouble.
+
+When gold began to grow less in the California gravel, the miners
+looked for it in the rocks on the mountain-side. The placer miners
+laughed at them and called their shafts "coyote holes"; but in time
+the placers failed, while nearly all of our gold to-day comes from
+veins of white quartz in the rocks. A vein of gold is the most
+capricious thing in the world. It may be so tiny that it can hardly be
+seen, then widen and grow rich in gold, then suddenly come to an end.
+This is why a new mine is so uncertain an enterprise. The gold may
+hold out and bring fortunes to the investors, or it may fail, and then
+all they will have to show for their money is the memory that they
+put it into a hole in the ground. The managers of a few of the
+well-established mines, however, have explored so far as to make sure
+that there is gold enough for many years of digging.
+
+The mining engineer must be a very wide-awake man. It is not enough
+for him simply to remember what was taught him in the schools of
+mining; he must be bright enough to invent new ways of meeting
+difficulties. No two mines are alike, and he must be ready for all
+sorts of emergencies. A gold mine now consists of a shaft or pit dug
+several hundred feet down into the rock, with levels or galleries
+running off from it and with big openings like rooms made where the
+rock was dug out. The roofs of the rooms are supported by great
+timbers. To break away the rock, the miner makes a hole with a rock
+drill worked by electricity or compressed air, puts powder or dynamite
+into the hole and explodes it. The broken rock is then raised to the
+surface and crushed in a "stamping mill." Here the ore is fed into a
+great steel box called a "mortar." Five immense hammers, often
+weighing a thousand pounds apiece, drop down upon the ore, one after
+another, until it is fine enough to go through a wire screen in the
+front of the box. When two hundred or more of these hammers are
+pounding away with all their might, a stamping mill is a pretty noisy
+place. The ore, crushed to a fine mud, now runs over sloping tables
+covered with copper. Sticking to the top of the copper is a film of
+quicksilver. This holds fast whatever gold there may be and makes an
+amalgam, which is scraped off from time to time, and the quicksilver
+is driven from the gold by heat.
+
+Gold that is not united with other metals is called "free milling
+gold." Much of it, however, is found in combination with one metal or
+another, and is known as "rebellious" or "refractory" gold. Such gold
+may sometimes be set free by heat, and sometimes by chemicals. One way
+is by the use of chlorine gas, and the story of it sounds almost like
+"The house that Jack built." It might run somewhat like this: This is
+the salt that furnishes the chlorine. This is the chlorine gas that
+unites with the gold. This is the chloride that is formed when the
+chlorine gas unites with the gold. This is the water that washes from
+the tank the chloride that is formed when the chlorine gas unites with
+the gold. This is the sulphate of iron that unites with the chlorine
+gas of the chloride that the water washes from the tank that is formed
+when the chlorine gas unites with the gold--and leaves the gold free.
+
+Another method is by the use of cyanide. More than a century ago a
+chemist discovered that if gold was put into water containing a little
+cyanide, the gold would dissolve, while quartz and any metals that
+might be united with the gold would settle in the tank. The water in
+which the gold is dissolved is now run into boxes full of shavings of
+zinc and is "precipitated" upon them; that is, the tiny particles of
+gold in the water fall upon the zinc and cling to it. Zinc melts more
+easily than gold, so if this gilded zinc is put into a furnace, the
+zinc melts and the gold is set free.
+
+Very often gold is found combined with lead or copper. It must then be
+melted or smelted in great furnaces. The metal is heavier than the
+rock and settles to the bottom of the furnace. It is then drawn off
+and the gold is separated from the other metals, usually by
+electricity.
+
+Sometimes large pieces of gold called "nuggets" are found by miners.
+The largest one known was found in Australia. It weighed 190 pounds
+and was worth $42,000. Sometimes spongy lumps of gold are found; but
+as a general thing gold comes from the little specks scattered through
+veins in rock, and much work has to be done before it can be made into
+coins or jewelry. It is too soft for such uses unless some alloy,
+usually copper or silver, is mixed with it to make it harder.
+Sometimes it is desirable to know how much alloy has been added. The
+jeweler then makes a line with the article on a peculiar kind of black
+stone called a "touchstone," and by the color of the golden mark he
+can tell fairly well how nearly pure the article is. To be more
+accurate, he pours nitric acid upon the mark. This eats away the alloy
+and leaves only the gold.
+
+Gold is a wonderful metal. It is of beautiful color; it can be
+hammered so thin that the light will shine through it; few acids
+affect it, and the oxygen which eats away iron does not harm it. Pure
+gold is spoken of as being "twenty-four carats fine," from _carat_, an
+old weight equal to one twenty-fourth of an ounce troy. Watchcases
+are from eight to eighteen carats fine; chains are seldom more than
+fourteen; and the gold coins of the United States are about eleven
+parts of gold and one of copper. Coins wear in passing from one person
+to another, and that is why the edges are milled, so that it may be
+more easily seen when they have become too light to be used as coins.
+When such pieces come into the hands of the Government, they must be
+recoined.
+
+
+
+
+VI
+
+THE STORY OF A SILVER MINE
+
+
+A man who goes out in search of a mine is called a "prospector." The
+best prospector is a man who has learned to keep his eyes open and to
+recognize the signs of gold and silver and other metals. A faithful
+friend goes with him, a donkey or mule which carries his bacon and
+beans, blankets, saucepan, and a few tools, such as a pan, pick,
+shovel, hammer, and axe. Sometimes the prospector also takes with him
+a magnifying glass and a little acid to test specimens, but usually he
+trusts to his eyes alone.
+
+When these few things have been brought together, the prospector and
+the donkey set out. They wander over the hills and down into the
+canyons. If a rock is stained red, the prospector examines it to see
+whether it contains iron; if it is green, he looks for copper. In the
+canyons and along the creeks he often tests the gravel for traces of
+some valuable metal. If he finds any of these traces along the stream,
+he follows them on the bank until they stop; then he carefully
+examines the bank of the stream or the nearest hillside. If he
+continues to find bits of metal, they will lead him to a vein of ore,
+from which they have been broken by the wind, rain, and frost.
+
+Generally a prospector is looking for some one special metal, and in
+his search he often overlooks some other metal; for instance,
+thousands of the gold-seekers who rushed to California in 1849 hurried
+through Nevada on their way. If they had only known what was under
+their feet, they would have taken their picks and shovels and begun to
+dig, instead of trying to get out of the region as soon as might be.
+Ten years later, the California placers were becoming exhausted, and
+miners began to go elsewhere in their search for gold.
+
+Among those who were working in what is now the State of Nevada were
+two Irishmen who had been unlucky in California and had fared no
+better in Nevada. They wanted to go somewhere else, but they had not
+money enough for the journey; so they kept on with their work at the
+foot of Mount Davidson, washing the gravel and saving the little gold
+that they found. They were annoyed by some heavy black stuff that
+united with the quicksilver in their cradles, interfered with the
+saving of the gold, and put them in a very bad temper. At length a man
+named Henry Comstock came along, who told them that this black stuff
+was silver ore. They examined the mountain-side, and discovered the
+outcrop or edge of a great vein containing gold and also silver. It is
+no wonder that people rushed from the east and west to the wonderful
+new mines, for it was plain that these new "diggings" were not mere
+placers, but rich veins that many years of working might not exhaust.
+Every newcomer hoped to discover a vein; and within a year or two the
+district around the Comstock lode was full of deep shafts, many of
+them abandoned and half-hidden by low brush, but some of them yielding
+quantities of gold and silver. Before this, there had been only about
+a thousand people in what is now Nevada, but in two years after the
+discovery of silver, there were 16,000, and a new Territory was
+formed.
+
+The miners knew how to get gold out of ore, but silver was another
+matter, and some of it was difficult to extract. They had so much
+trouble that they were ready to believe in any treatment of the ore,
+no matter how absurd, that promised to help them out of their
+difficulties. Some of them were actually persuaded that the juice of
+the wild sagebrush would bring the silver out. It is no wonder that
+they were troubled, for in the Comstock lode were not only gold and
+silver, but ten or twelve other metals or combinations of silver with
+something else. At length processes were invented for treating the
+different kinds of ore. Some kinds were crushed in a stamping mill,
+then ground to a powder and mixed with quicksilver or mercury. This
+mercury united with both the gold and the silver, making an amalgam.
+The amalgam, together with the finely ground ore, was put into a
+"settler," and here the heavy amalgam sank to the bottom and was then
+strained. The extra mercury was collected, and the amalgam was put
+into a retort or kettle and heated. The mercury became a gas and was
+driven off from the gold and silver, then caught in a vessel cool
+enough to condense it, just as a cold plate held in steam will
+collect drops of water. Sometimes the ore was mixed with copper and
+lead. In that case common salt and copper sulphate were used. Some ore
+had to be roasted in a furnace in order to drive off the sulphur.
+
+[Illustration: THE STORY OF A SPOON
+
+_Courtesy The Gorham Co._
+
+(1) Silver strip blanked. (2) Pinched. (3) Graded. (4) Outlining of
+Handle. (5) Stamped Handle. (6) Spoon completely trimmed. (7, 8)
+Finished spoons.]
+
+There were great and unusual dangers to be met in getting the ore. The
+vein of quartz which bore it was fifty or sixty feet wide. Some was
+hard, and some so soft and crumbling that pillars would not hold up
+the roof. The passageways were then lined with heavy logs standing on
+either side, other logs laid across their tops, and all bolted firmly
+together. Nevertheless, they twisted and fell, and slowly but
+certainly the whole mass of earth and rock, two hundred or more feet
+in thickness, was coming down upon the heads of the miners. The work
+on the Comstock mines had come to an end unless a man could be found
+able to invent some system of support not laid down in the books. The
+man was found. He took short, square timbers five or six feet long,
+put them together as if they were the sides and ends of square boxes,
+and piled them one above another, making hollow pillars. He fastened
+these firmly together and filled the space inside with waste rock,
+thus making strong, solid pillars that would support almost any weight
+that could be put upon them.
+
+There were two other dangers, water and heat. The vein was porous and
+water was constantly trickling out of it. Then, too, there were "water
+pockets," or natural reservoirs in the rock, and any moment the
+stroke of a pick might let out a torrent and force the miners to run
+for their lives. Sometimes minerals were dissolved in this water, and
+the men with closed eyes and swollen faces had to be hurried to the
+surface for treatment. Powerful pumps had to be used and the water
+sent away through long lines of pipes. This water was warm, and in
+very deep workings in the Comstock vein it was boiling hot. Even with
+quantities of ice sent down to cool them, the men could work in some
+places only a short time.
+
+In San Francisco there was a mining engineer named Adolph Sutro who
+planned to remedy these troubles by driving a big four-mile tunnel
+through the heart of the mountain, letting out the hot water and the
+foul air. The owners of some of the mines joined him in raising the
+money, and the tunnel was dug. Through this the water ran out. The
+mines were freed of foul air and fresh air was driven in.
+
+The Comstock lode has given up an amazing amount of precious metal.
+Between 1860 and 1890 it produced $340,000,000. After 1890, however,
+its product grew less. The vein was not so rich, the price of silver
+fell, while the cost of mining it at great depths increased. Not
+nearly so much was mined, and at length water rose in the mines up to
+the level of the Sutro Tunnel. In 1900 new machinery was put in and
+new methods were adopted, such as treating the tailings with cyanide
+and so saving much of the precious metal from them. From the beginning
+the Comstock mines have been so ready to follow improved methods that
+they have been called the mining school of the world.
+
+Great quantities of silver are used for making jewelry and for
+tableware. The one objection to its use is that silver likes to unite
+with sulphur, and thus the silver easily becomes black. There is
+sulphur in the yolk of an egg and that is why the spoon with which it
+has been eaten turns black. Even if silverware is not used, it
+tarnishes, especially in towns, because there is so much sulphureted
+hydrogen in the air. In perfectly pure air, it would not tarnish.
+Silver is harder than gold, but not hard enough to be used without
+some alloy, usually copper. Tableware is "solid" even if it contains
+alloy enough to stiffen it. It is "plated" if it is made of some
+cheaper metal and covered with silver. The old way of doing this was
+to fasten with bits of solder a thin sheet of silver to the cup or
+vase or whatever was in hand and heat it. This did fairly well for
+large, smooth articles; but it was almost impossible to finish the
+edges of spoons so as not to show the two metals. If you look at a
+plated spoon to-day, however, you will find that there is no break at
+the edge, and so far as you can tell by the eye, it is solid silver.
+If you look on the back of the spoon, you will perhaps see "Rogers
+Bros. 1846." These men were the first silvermakers in this country to
+plate tableware by electricity. To make a spoon, they formed one out
+of iron or copper and made sure that it was perfectly clean. Then
+across a bath of silver cyanide, potassium cyanide, and water they
+laid two metal rods, and from these they hung a spoon at one end and a
+plate of silver at the other. These rods were connected with the two
+poles of a battery. The electrical current passed through them,
+released the silver from the silver cyanide, and this was deposited
+upon the spoon. The cyanide that had lost its silver took enough more
+from the silver plate to make up. The amount of silver on the spoon
+depends upon the length of time it remains in the bath. It is weighed
+before plating and again afterwards, to make sure that the proper
+amount of silver has been deposited upon it. On the back of many
+plated articles you will see the words "Triple plate" or "Quadruple
+plate." If the article has been made by a reliable firm, this means
+that the triple plate it manufactures contains three times as much
+silver as "single plate," and that quadruple plate contains four times
+as much. A piece of silver looks just as well if it has stayed in the
+bath only a few minutes, but of course it has taken on so little
+silver that this will soon wear off and show the cheaper metal.
+
+A large amount of silver is used for coins. When the United States
+needs dollars, half-dollars, quarters, and dimes, notice is given and
+offers are called for, stating the quantity for sale and its price.
+When it is delivered, it is first of all "assayed"; that is, tested to
+find out how nearly pure it is and how much it is worth. Next it is
+refined, or purified from other metals, mixed with a little copper to
+harden it, then melted again and poured into moulds to make bars. If
+dollars are to be made, the bar is made thinner by passing it between
+heavy rollers, and blanks for dollars are cut out with a die. These
+blanks are weighed and every one that is too heavy or too light is put
+back to be melted over again. Thus far these dollars are only round,
+smooth pieces of metal. They must be milled to give them a rough edge,
+and they must be stamped. For stamping, the piece of metal is placed
+between two dies, one above and one below, and these close upon it
+with a force of one hundred and fifty tons. Every part of the process
+of manufacturing money is carried on with the utmost care. The places
+where coins are made are called "mints." The United States has four;
+the oldest is in Philadelphia, and there are branch mints in San
+Francisco, New Orleans, and Denver. Coins minted in Philadelphia have
+no distinguishing mark; but coins minted in San Francisco are marked
+with a tiny "S"; if minted in New Orleans, with an "O"; and if in
+Denver, with a "D."
+
+
+
+
+VII
+
+IRON, THE EVERYDAY METAL
+
+
+Did you ever realize that your food and clothes, your books, and the
+house in which you live all depend upon iron? Vegetables, grains, and
+fruits are cultivated with iron tools; fish are caught with iron
+hooks, and many iron articles are used in the care and sale of meat.
+Clothes are woven on iron looms, sewed with iron needles, and fastened
+together with buttons containing iron. Books are printed and bound by
+iron machines, and sometimes written with iron pens or on iron
+typewriters. Houses are put together with nails; and indeed, there is
+hardly an article in use that could be made as well or as easily if
+iron was not plenty. If you were making a world and wanted to give the
+people the most useful metal possible, the gift would have to be iron;
+and the wisest thing you could do would be to put it everywhere, but
+in such forms that the people would have to use their brains to make
+it of service.
+
+This is just the way with the iron in our world. Wherever you see a
+bank of red sand or red clay or a little brook which leaves a red mark
+on the ground as it flows, there is iron. Iron is in most soils, in
+red bricks, in garnets, in ripening apples, and even in your own
+blood. It forms one twentieth part of the crust of the earth. Iron
+dissolves in water if you give it time enough. If you leave a steel
+tool out of doors on a wet night, it will rust; that is, some of the
+iron will unite with the oxygen of the water. This is rather
+inconvenient, and yet in another way this dissolving is a great
+benefit. Through the millions of years that are past, the oxygen of
+the rain has dissolved the iron in the hills and has worked it down,
+so that now it is in great beds of ore or in rich "pockets" that are
+often of generous size. One of them, which is now being mined in
+Minnesota, is more than two miles long, half a mile wide, and of great
+thickness. The rains are still at work washing down iron from the
+hills. They carry the tiny particles along as easily as possible until
+they come upon limestone. Then, almost as if it was frightened, the
+brook drops its iron and runs away as fast as it can. Sometimes it
+flows into a pond or bog in which are certain minute plants or animals
+that act as limestone does, and the particles of iron fall to the
+bottom of the pond. In colonial days much of the iron worked in
+America was taken from these deposits. One kind of iron is of special
+interest because it comes directly from the sky, and falls in the
+shape of stones called "meteorites," some of which weigh many tons. In
+some of the old fables about wonderful heroes, the stories sometimes
+declare that the swords with which they accomplished their deeds of
+prowess fell straight from the heavens, which probably means that they
+were made of meteoric iron. Fortunately for the people and their
+homes, meteorites are not common, but every large museum has
+specimens of them.
+
+It is not especially difficult to make iron if you have the ore, a
+charcoal fire in a little oven of stones, and a pair of bellows. Put
+on layers of charcoal alternating with layers of ore, blow the
+bellows, and by and by you will have a lump of iron. It is not really
+melted, but it can be pounded and worked. This is called the "Catalan
+method," because the people of Catalonia in Spain made iron in this
+way. It is still used by the natives of the interior of Africa. But if
+all the iron was made by this method, it would be far more costly than
+gold. The man who makes iron in these days must have an immense "blast
+furnace," perhaps one hundred feet high, a real "pillar of fire." Into
+this furnace are dropped masses of ore, and with it coke to make it
+hotter and limestone to carry off the silica slag, or worthless part.
+To increase the heat, blasts of hot air are blown into the bottom of
+the furnace. This air is heated by passing it through great steel
+cylinders as high as the furnace. The fuel used is nothing more than
+the gases which come out at the top of the furnace.
+
+The slag is so much lighter than iron that when the ore is melted the
+slag floats on top just as oil floats on water, and can be drained out
+of the furnace through a higher opening than that through which the
+iron flows. The slag tap is open most of the time, but the iron tap is
+opened only once in about six hours. It is a magnificent sight when a
+furnace is "tapped" and the stream of iron drawn off. Imagine a great
+shed, dark and gloomy, with many workmen hurrying about to make ready
+for what is to come. The floor is of sand and slopes down from the
+furnace. Through the center of this floor runs a long ditch straight
+from the furnace to the end of the shed. Opening from it on both sides
+are many smaller ditches; and connecting with these are little
+gravelike depressions two or three feet long and as close together as
+can be. These are called "pigs." When the time has come, the workmen
+gather about the furnace, and with a long bar they drill into the
+hard-baked clay of the tapping hole. Suddenly it breaks, and with a
+rush and a roar the crimson flood of molten iron gushes out. It flows
+down the trench into the ditches, then into the pigs, till their whole
+pattern is marked out in glowing iron. Now the blast begins to drive
+great beautiful sparks through the tapping hole. This means that the
+molten iron is exhausted. The blast is turned off, and the "mud-gun"
+is brought into position and shoots balls of clay into the tapping
+hole to close it for another melting, or "drive." The crimson pigs
+become rose-red, darken, and turn gray. The men play streams of water
+over them and the building is filled with vapor. As soon as the pigs
+are cool enough, they are carted away and piled up outside the
+building.
+
+In some iron works moulds of pressed steel carried on an endless chain
+are used instead of sand floors. The chain carries them past the mouth
+of a trough full of melted iron. They are filled, borne under water
+to be cooled, and then dropped upon cars. A first-class machine can
+make twenty pigs a minute.
+
+[Illustration: IN THE STEEL FOUNDRY
+
+It is a dangerous business to visit a steel mill. Tremendous kettles
+travel overhead on huge cranes, hot metal flows from unexpected
+places, and there is a constant glow and steam and roar everywhere to
+confuse the unwary.]
+
+Most of the iron made in blast furnaces is turned into steel. Steel
+has been made for centuries, but until a few years ago the process was
+slow and costly. A workman's steel tools were treasures, and a good
+jackknife was a valuable article. Railroads were using iron rails.
+They soon wore out, but at the suggestion to use steel, the presidents
+of the roads would have exclaimed, "Steel, indeed! We might as well
+use silver!" Trains needed to be longer and heavier, but iron rails
+and bridges could not stand the strain. Land in cities was becoming
+more valuable; higher buildings were needed, but stone was too
+expensive. Everywhere there was a call for a metal that should be
+strong and cheap. Iron was plentiful, but steel was dear. A cheaper
+method of making iron into steel was needed; and whenever there is
+pressing need of an invention, it is almost sure to come. Before long,
+what is known as the "Bessemer process" was invented. One great
+difficulty in the manufacture of steel was to leave just the right
+amount of carbon in the iron. Bessemer simply took it all out, and
+then put back exactly what was needed. Molten iron, tons and tons of
+it, is run into an immense pear-shaped vessel called a "converter."
+Fierce blasts of air are forced in from below. These unite with the
+carbon and destroy it. There is a roar, a clatter, and a clang.
+Terrible flames of glowing red shoot up. Suddenly they change from red
+to yellow, then to white; and this is the signal that the carbon has
+been burned out. The enormously heavy converter is so perfectly poised
+that a child can move it. The workmen now tilt it and drop in whatever
+carbon is needed. The molten steel is poured into square moulds,
+forming masses called "blooms," and is carried away. More iron is put
+into the converter, and the work begins again.
+
+The Bessemer process makes enormous masses of steel and makes it very
+cheaply; but it has one fault--it is too quick. The converter roars
+away for a few minutes, till the carbon and other impurities are
+burned out; and the men have no control over the operation. In what is
+called the "open-hearth" process, pig iron, scrap iron, and ore are
+melted together with whatever other substances may be needed to make
+the particular kind of steel desired. This process takes much longer
+than the Bessemer, but it can be controlled. Open-hearth steel is more
+homogeneous,--that is, more nearly alike all the way through,--and is
+better for some purposes, while for others the Bessemer is preferred.
+
+Steel is hard and strong, but it has two faults. A steel bar will
+stand a very heavy blow and not break, but if it is struck gently many
+thousand times, it sometimes crystallizes and may snap. A steel rail
+may carry a train for years and then may crystallize and break and
+cause a wreck. Inventors are at work discovering alloys to prevent
+this crystallization. The second fault of steel is that it rusts and
+loses its strength. That is why an iron bridge or fence must be kept
+painted to protect it from the moisture in the air.
+
+If all the iron that is in use should suddenly disappear, did you ever
+think what would happen? Houses, churches, skyscrapers, and bridges
+would fall to the ground. Railroad trains, automobiles, and carriages
+would become heaps of rubbish. Ships would fall apart and become only
+scattered planks floating on the surface of the water. Clocks and
+watches would become empty cases. There would be no machines for
+manufacturing or for agriculture, not even a spade to dig a garden.
+Everybody would be out of work. If you wish to see how it would seem,
+try for an hour to use nothing that is of iron or has been made by
+using iron.
+
+
+
+
+VIII
+
+OUR GOOD FRIEND COPPER
+
+
+Where did rocks come from?
+
+Some were deposited in water, like limestone and like the shale and
+sandstone that lie over the strata of coal. Others were made by fire,
+and were thrown up in a melted state from the interior of the earth.
+Such rocks are the Giant's Causeway in Ireland and the Palisades of
+the Hudson River. They are called "igneous" rocks, from the Latin word
+_ignis_ meaning "fire."
+
+When the igneous rocks were thrown up to the surface of the earth,
+they brought various metals with them. How the metals happened to be
+there ready to be brought up, no one knows. Some people think they
+were dissolved in water and then deposited; others think that
+electricity had something to do with their formation. However that may
+be, metals were brought up with the igneous rocks, and one of these
+metals is copper.
+
+Now, to one who did not know how to work iron, copper was indeed a
+wonderful treasure, for it made very good knives and spoons. The
+people who lived in this country long before the Indians came
+understood how to use it, and after a while the Indians themselves
+found out its value. They did not trouble themselves to dig for it;
+they simply picked it up from the ground, good pure metal in lumps;
+and with stones for hammers they beat it into knives.
+
+There was only one place in what is now the United States where they
+could do this, and that was in northern Michigan. A long point of land
+stretches out into Lake Superior as if it was trying to see what could
+be found there. Just beyond its reach is Isle Royal; and in these two
+places there was plenty of copper, enough for the Indians, enough for
+the people who have come after them, and enough for a great many more.
+One piece of copper which the Indians did not pick up, and the United
+States Government did, is the famous Ontonagon Boulder, so called
+because it was found near the Ontonagon River. It weighs more than
+three tons. The Indians would have been glad to make use of it, but it
+was too hard for their tools, and so they are said to have worshiped
+it as a god. It is now in the National Museum in Washington.
+
+The lumps of copper, such as those which delighted the hearts of the
+Indians, are known to-day as "barrel" copper, because they are of a
+good size to be dropped into barrels and carried away for smelting.
+The great boulders which the Indians could not use are called "mass"
+copper. Sometimes they weigh as much as five hundred tons. The copper
+in them is almost pure, and a big boulder is worth perhaps $200,000.
+Nevertheless, the mine-owners do not rejoice when they come upon such
+a mass in their digging, for it cannot be either dug or blasted, and
+has to be cut away with chisels of chilled steel. Now, a mine may be
+wonderfully rich in metal, but if working it costs too much, then
+another mine with less metal but more easily worked will pay better.
+So it is with these great masses of copper. They are interesting to
+study and they look well in museums, but they do not pay so well as
+the "stamp" copper which is found in humble little bits in the gangue,
+or the rock of the vein, and has to be pounded in a stamp mill. This
+gangue is dug out and broken up as in mines of other metals. The
+copper is much heavier than the rock, so it is easy to get rid of the
+worthless gangue by means of a flow of water. The gangue of the
+Michigan mines is exceedingly hard, but the stamps are so powerful
+that one can crush five hundred tons in less than twenty-four hours.
+Some copper can be taken out of the mortars at once, but the rest of
+the broken gangue is fed to jigs, or screens, which are kept under
+jets of water. The water is thrown up from below and the lighter rock
+is tossed away, while the heavier copper falls through the tiny holes
+in the screens.
+
+[Illustration: IN A COPPER SMELTER
+
+The men are pouring hot copper into moulds for castings.]
+
+After the ore has been through all these experiences, it comes out
+looking like dark-colored sand or coarse brown sugar. It is not
+interesting, and no one who saw it for the first time would ever fancy
+that it was going to turn into something beautiful. It is dumped into
+freight cars and trundled off to the smelting furnaces. But however
+uninteresting it looks, it is well worth while to follow these cars to
+see what happens to it at the smelters. First of all, even before it
+goes into the smelting furnace, it must be roasted. There is usually
+sulphur combined with the copper, and roasting will get rid of much of
+it. In some places this is done by building up a great heap of ore
+with a little wood. The wood is kindled, and by the time it has burned
+out, the sulphur in the ore has begun to burn, and in a good-sized
+heap it will continue to burn for perhaps two months.
+
+Such a heap is a good thing to keep away from, for the fumes of
+sulphur are very disagreeable. Indeed, they will kill trees and other
+growing things wherever the wind may carry them, even several miles
+away. The managers of mines of copper as well as of gold and silver
+have learned to economize; and it has been found that instead of
+letting these fumes go into the air, they may be made to pass through
+acid chambers lined with zinc and full of water. The water holds the
+fumes, and can be used in making sulphuric acid.
+
+After the ore has been roasted, it is put into the furnace for
+smelting. If you should make an oven and put into it a mixture of wood
+and roasted copper, that would be a smelting furnace. Set the wood on
+fire, pump in air to make the flame hot, and if your furnace could be
+made hot enough,--that is, 2300° F., or about eleven times as hot as
+boiling water,--you could smelt copper. Of course the furnace of a
+real smelting factory will hold tons and tons of copper ore and has
+all sorts of improvements, but after all it is in principle only an
+oven with wood and ore and draft. Another sort of furnace, which is
+better for some kinds of ore, has a grate for the fire and a bed above
+it for the copper.
+
+Imagine an enormous furnace holding between two and three hundred tons
+of metal and burning with such a terrific heat that by contrast
+boiling water would seem cool and comfortable. Suddenly, while you
+stand looking at it, but a long way off, a door flies open and the
+most beautiful cascade--only it is not a waterfall, but a _copper_
+fall--pours out. It looks like red, red gold, rich and wonderful, with
+little flames of red and blue dancing over it. It might almost be one
+of the fire-breathing dragons of the old story-books; and if it should
+get loose, it would devour whomever it touched far quicker than any
+dragon. It hardly seems as if any one could manage such a monster; but
+it looks easy, after you have seen it done. An enormous horizontal
+wheel revolves slowly. On its edge are moulds shaped like bricks, but
+much larger. On the hub of the wheel a workman sits to direct the
+filling of these. A set of them is filled, and moves on, and others
+take their place. When they are partly cooled, another workman, at the
+farther side of the wheel, pries them out of the mould and drops them
+into water. Then by the aid of the fingers of a machine and those of
+men, they are loaded upon cars.
+
+In copper there is often some gold and silver. The precious metals do
+not make the copper any better, and if they can be separated from it,
+they are well worth the trouble. This is done by electricity. It is so
+successful that the metallurgists are hoping soon to take a long step
+ahead and by means of electricity to produce refined copper directly
+from the ore. Indeed, this has been done already in the laboratories,
+but before the managers of mines can employ the method, a way of
+making it less expensive must be discovered.
+
+No mine that wastes anything is as well managed as it might be; and
+superintendents are constantly on the watch for cheaper methods and
+for ways to make the refuse matter of use. Even the scoria, or slag
+from the furnaces, has been found to be good for something, and now it
+is made into a coarse sort of brick that for certain rough uses is of
+value. By the way, the shaft of a copper mine, the Red Jacket, has
+shown itself of use in a manner that no one expected, namely, it helps
+to prove that the earth turns around. This shaft is the deepest mining
+shaft in the world, and when you get into the cage, you go down a full
+mile toward the center of the earth. If you drop any article into the
+shaft, it always strikes the east side before reaching the bottom. The
+only way to explain this is that the earth turns toward the east.
+
+Copper mixed with zinc forms brass, which is harder than copper alone.
+It tarnishes, though not so easily as copper; but a coat of varnish
+will protect it till the varnish wears off. A good way to find out the
+many uses of brass and to see how valuable they are is to go along the
+street and through a house and make a list. On the street you will see
+signs, harness buckles, and buttons, everywhere. Look on the
+automobiles and fire engines for a fine display of brass, polished and
+shining. In the house you will find brass bedsteads, curtain rods,
+faucets, pipes, drawerpulls, candlesticks, gas and electric fixtures,
+lamps, the works of clocks and watches, and scores of other things.
+You will not have any idea how many they are till you begin to count.
+
+Copper mixed with tin forms bronze. Go into a hardware store and look
+at the samples of bronze outside of each drawer, and you will be
+surprised that there are so many. Bronze does not change even when in
+the open air for ages. That is one reason why it has always been so
+much used for statues. There are two strange facts about this mixture.
+One is that bronze is harder than either copper or tin. The other is
+that if you mix one pint of melted copper with one pint of tin, the
+mixture will be less than a quart. Just why these things are so, no
+one is quite certain. Mathematics declares that the whole is equal to
+the sum of its parts; but in this one case the whole seems to be less
+than the sum of its parts.
+
+Another reason why bronze is so much used for statues is that the
+castings are smooth. I once went to a foundry to have a brass ornament
+shaped somewhat like a cone made for a clock. The foundryman formed a
+mould in clay and poured the melted brass into it. When it had cooled,
+the mould was broken off and the ornament taken out; but it was of no
+use because it was so full of little hollows that it could not be made
+smooth without cutting away a great deal of it. The man had to try
+three times before he succeeded in making one that could be polished.
+If it had been made of bronze, there would have been no trouble,
+because bronze, hard as it is after it cools, flows when it is melted
+almost as easily as molasses and fills every little nook and corner of
+the mould.
+
+A famous Latin poet named Horace, who lived two thousand years ago,
+wrote of his poems, "I have reared a monument more lasting than
+bronze"; and he was right, for few statues have endured from his day
+to ours, but his poems are still read and admired.
+
+Bells are made of bronze, about three quarters copper and one quarter
+tin. It is thought that much copper gives a deep, full tone, and that
+much tin with, sometimes, zinc makes the tone sharp. The age of a bell
+has something to do with its sound being rich and mellow; but the
+bellmaker has even more, for he must understand not only how to cast
+it, but also how to tune it. If you tap a large bell, it will, if
+properly tuned, sound a clear note. Tap it just on the curve of the
+top, and it will give a note exactly one octave above the first. If
+the note of the bell is too low, it can be made higher by cutting away
+a little from the inner rim. If it is too high, it can be made lower
+by filing on the inside a little above the rim. Many of the old bells
+contain the gifts of silver and gold which were thrown in by people
+who watched their founding. The most famous bell in the United States
+is the "Liberty Bell" of Independence Hall, in Philadelphia, which
+rang when Independence was adopted by Congress. This was founded in
+England long before the Revolution and later was melted and founded
+again in the United States.
+
+It would not be easy to get on without brass and bronze; but even
+these alloys are not so necessary as copper by itself. It is so strong
+that it is used in boiler tubes of locomotives, as roofing for
+buildings and railroad coaches, in the great pans and vats of the
+sugar factories and refineries. A copper ore called "malachite," which
+shows many shades of green, beautifully blended and mingled, is used
+for the tops of tables. Wooden ships are often "copper-bottomed"; that
+is, sheets of copper are nailed to that part of the hull which is
+under water in order to prevent barnacles from making their homes on
+it, and so lessening the speed of the vessel.
+
+People often say that the latter half of the nineteenth century was
+the Age of Steel, because so many new uses for steel were found at
+that time. The twentieth century promises to be the Age of
+Electricity, and electricity must have copper. Formerly iron was used
+for telegraph wires; but it needs much more electricity to carry power
+or light or heat or a telegraphic message over an iron wire than one
+of copper. Moreover, iron will rust and will not stretch in storms
+like copper, and so needs renewing much oftener. Electric lighting and
+the telephone are everywhere, even on the summits of mountains and in
+mines a mile below the earth's surface. Electric power, if a
+waterfall furnishes the electricity, is the cheapest power known. The
+common blue vitriol is one form of copper, and to this we owe many of
+our electric conveniences. It is used in all wet batteries, and so it
+rings our doorbells for us. It also sprays our apple and peach trees,
+and is a very valuable article. Indeed, copper in all its forms, pure
+and alloyed, is one of our best and most helpful friends.
+
+
+
+
+IX
+
+THE NEW METAL, ALUMINUM
+
+
+Not many years ago a college boy read about an interesting metal
+called "aluminum." It was as strong as iron, but weighed only one
+third as much, and moisture would not make it rust. It was made of a
+substance called "alumina," and a French chemist had declared that the
+clay banks were full of it; and yet it cost as much as silver. It had
+been used in France for jewelry and knicknacks, and a rattle of it had
+been presented to the baby son of the Emperor of France as a great
+rarity.
+
+The college boy thought by day and dreamed by night of the metal that
+was everywhere, but that might as well be nowhere, so far as getting
+at it was concerned. At the age of twenty-one, the young man
+graduated, but even his new diploma could not keep his mind away from
+aluminum. He borrowed the college laboratory and set to work. For
+seven or eight months he tried mixing the metal with various
+substances to see if it would not dissolve. At length he tried a stone
+from Greenland called "cryolite," which had already been used for
+making a kind of porcelain. The name of this stone comes from two
+Greek words meaning "ice stone," and it is so called because it melts
+so easily. The young student melted it and found that it would
+dissolve alumina. Then he ran an electric current through the melted
+mass, and there was a deposit of aluminum. This young man, just out of
+college, had discovered a process that resulted in reducing the cost
+of aluminum from twelve dollars a pound to eighteen cents. Meanwhile a
+Frenchman of the same age had been working away by himself, and made
+the same discovery only two months later.
+
+Aluminum is now made from a mineral called "bauxite," found chiefly in
+Georgia, Alabama, and Arkansas. Mining it is much more agreeable than
+coal mining, for the work is done aboveground. The bauxite is in beds
+or strata which often cover the hills like a blanket. First of all,
+the mine is "stripped,"--that is, the soil which covers the ore is
+removed,--and then the mining is done in great steps eight or ten feet
+high, if a hill is to be worked. There is some variety in mining
+bauxite, for it occurs in three forms. First, it may be a rock, which
+has to be blasted in order to loosen it. Second, it may be in the form
+of gray or red clay. Third, it occurs in round masses, sometimes no
+larger than peas, and sometimes an inch in diameter. In this form it
+can easily be loosened with a pickaxe, and shoveled into cars to be
+carried to the mill. Bauxite is a rather mischievous mineral and
+sometimes acts as if it delighted in playing tricks upon managers of
+mines. The ore may not change in the least in its appearance, and yet
+it may suddenly have become much richer or much poorer. Therefore the
+superintendent has to give his ore a chemical test every little while
+to make sure that all things are going on well.
+
+This bauxite is purified, and the result is a fine white powder, which
+is pure alumina, and consists of the metal aluminum and the gas
+oxygen. Cryolite is now melted by electricity. The white powder is put
+into it, and dissolves just as sugar dissolves in water. The
+electricity keeps on working, and now it separates the alumina into
+its two parts. The aluminum is a little heavier than the melted
+cryolite, and therefore it settles and may be drawn off at the bottom
+of the melting-pot.
+
+There are a good many reasons why aluminum is useful. As has been said
+it is strong and light and does not rust in moisture. You can beat it
+into sheets as thin as gold leaf, and you can draw it into the finest
+wire. It is softer than silver, and it can be punched into almost any
+form. It is the most accommodating of metals. You can hammer it in the
+cold until it becomes as hard as soft iron. Then, if you need to have
+it soft again, it will become so by melting. It takes a fine polish
+and is not affected, as silver is, by the fumes which are thrown off
+by burning coal; and so keeps its color when silver would turn black.
+Salt water does not hurt it in the least, and few of the acids affect
+it. Another good quality is that it conducts electricity excellently.
+It is true that copper will do the same work with a smaller wire; but
+the aluminum is much lighter and so cheap that the larger wire of
+aluminum costs less than the smaller one of copper, and its use for
+this purpose is on the increase. It conducts heat as well as silver.
+If you put one spoon of aluminum, one of silver, and one that is
+"plated" into a cup of hot water, the handles of the first two will
+almost burn your fingers before the third is at all uncomfortable to
+touch.
+
+[Illustration: A "MOVIE" OF AN ALUMINUM FUNNEL
+
+_Courtesy The Aluminum Cooking Utensil Company._
+
+Seventeen other operations are necessary after the thirteenth stamping
+operation before the funnel is ready to be sold. And after all this
+work, we can buy it for 35 cents at any hardware store.]
+
+Aluminum is found not only in clay and indeed in most rocks except
+sandstone and limestone, but also in several of the precious stones,
+in the yellow topaz, the blue sapphire and lapis-lazuli, and the red
+garnet and ruby. It might look down upon some of its metallic
+relatives, but it is friendly with them all, and perfectly willing to
+form alloys with most of them. A single ounce of it put into a ton of
+steel as the latter is being poured out will drive away the gases
+which often make little holes in castings. Mixed with copper it makes
+a beautiful bronze which has the yellow gleam of gold, but is hard to
+work. When a piece of jewelry looks like gold, but is sold at too low
+a price to be "real," it may be aluminum bronze, very pretty at first,
+but before long its luster will vanish. Aluminum bronze is not good
+for jewelry, but it is good for many uses, especially for bearings in
+machinery. Aluminum mixed with even a very little silver has the color
+and brightness of silver. The most common alloys with aluminum are
+zinc, copper, and manganese, but in such small quantities that they do
+not change its appearance.
+
+With so many good qualities and so few bad ones, it is small wonder
+that aluminum is employed for more purposes than can be counted. A
+very few years ago it was only an interesting curiosity, but now it is
+one of the hardest-worked metals. Automobiles in particular owe a
+great deal to its help. When they first began to be common, in
+1904-05, the engines were less powerful than they are now made, and
+aluminum was largely employed in order to lessen the weight. Before
+long it was in use for carburetors, bodies, gear-boxes, fenders,
+hoods, and many other parts of the machine. Makers of electric
+apparatus use aluminum instead of brass. The frames of opera glasses
+and of cameras are made of it. Travelers and soldiers and campers,
+people to whom every extra ounce of weight counts, are glad enough to
+have dishes of aluminum. The accommodating metal is even used for
+"wallpaper," and threads of it are combined with silk to give a
+specially brilliant effect on the stage. It can be made into a paint
+which will protect iron from rust; and will make woodwork partially
+fireproof.
+
+Aluminum has been gladly employed by the manufacturers of all sorts of
+articles, but nowhere has its welcome been more cordial than in the
+kitchen. Any one who has ever lifted the heavy iron kettles which were
+in use not so very many years ago will realize what an improvement it
+is to have kettles made of aluminum. But aluminum has other advantages
+besides its lightness. If any food containing a weak acid, like
+vinegar and water, is put into a copper kettle, some of the copper
+dissolves and goes into the food; acid does not affect aluminum except
+to brighten it if it has been discolored by an alkali like soda. "Tin"
+dishes, so called, are only iron with a coating of tin. The tin soon
+wears off, and the iron rusts; aluminum does not rust in moisture. A
+strong alkali will destroy it, but no alkali in common use in the
+kitchen is strong enough to do more harm than to change the color, and
+a weak acid will restore that. Enameled ware, especially if it is
+white, looks dainty and attractive; but the enamel is likely to chip
+off, and, too, if the dish "boils dry," the food in it and the dish
+itself are spoiled. Aluminum never chips, and it holds the heat in
+such a manner as to make all parts of the dish equally hot. Food,
+then, is not so likely to "burn down," but if it does, only the part
+that sticks will taste scorched; and no matter how many times a dish
+"boils dry," it will never break. If you make a dent in it, you can
+easily pound it back into shape again. It is said that an aluminum
+teakettle one sixteenth of an inch in diameter can be bent almost
+double before it will break.
+
+Aluminum dishes are made in two ways. Sometimes they are cast, and
+sometimes they are drawn on a machine. If one is to be smaller at the
+top, as in the case of a coffeepot, it is drawn out into a cylinder,
+then put on a revolving spindle. As it whirls around, a tool is held
+against it wherever it is to be made smaller, and very soon the
+coffeepot is in shape. The spout is soldered on, but even the solder
+is made chiefly of aluminum.
+
+Aluminum dishes may become battered and bruised, but they need never
+be thrown away. There is an old story of some enchanted slippers which
+brought misfortune to whoever owned them. The man who possessed them
+tried his best to get rid of the troublesome articles, but they always
+returned. So it is with an aluminum dish. Bend it, burn it, put acid
+into it, do what you will to get rid of it, but like the slippers it
+remains with you. Unlike them, however, it brings good fortune,
+because it saves time and trouble and patience and money.
+
+A few years ago the motive power for most manufactures was steam.
+Electricity is rapidly taking its place; and if aluminum was good for
+nothing else save to act as a conductor of electricity in its various
+applications, there would even then be a great future before it.
+
+
+
+
+X
+
+THE OIL IN OUR LAMPS
+
+
+Probably the first man who went to a spring for a drink and found oil
+floating on the water was decidedly annoyed. He did not care in the
+least where the oil came from or what it was good for; he was thirsty,
+and it had spoiled his drink, and that was enough for him. We know now
+that oil comes chiefly from strata of coarse sandstone, but we are not
+quite sure how it happened to be there. The sand which formed these
+strata was deposited by water ages and ages ago--we are certain of
+that. Another thing that we are certain of is that where the strata
+lie flat, there is no oil. Hot substances become smaller as they cool;
+and as the earth grew cooler, it became smaller. The crust of the
+earth wrinkled as the skin of an apple does when it dries. In the tops
+of these great sandstone wrinkles there is often gas; and below the
+gas is the place where oil is found. There is no use in looking for
+petroleum where the folds of the strata are very sharp, because in
+that case the strata crack and let the oil flow away. It is not in
+pools, but the porous stone holds it just as a sponge holds water. If
+you drop a little oil upon a stone even much less porous than
+sandstone, it will not be easy to wipe it off, because some of it will
+have sunk into the stone.
+
+In many places the gas forces its way out, and is piped to carry to
+houses for light and heat. Not far above Niagara Falls there was a
+spring of gas which flowed for years. An iron pipe was put down, and
+when the gas was lighted, the flame shot up three or four feet. The
+gas came with such force that a handkerchief put over the end of the
+pipe would not burn, though the flame would blaze away above it. In
+the country of the fire worshipers, on the shores of the Caspian Sea,
+fires of natural gas have been burning for ages, kindled, perhaps, by
+lightning centuries ago. There is a vast supply of oil in this place;
+and indeed there is hardly a country that has not more or less of it.
+
+In the United States the colonists soon learned that there was
+petroleum in what is now the State of New York; but New York was a
+long way from the Atlantic seaboard in those days, and they went on
+contentedly burning candles or sperm whale oil, or, a little later, a
+rather dangerous liquid which was known as "fluid." The Indians
+believed that the oil which appeared in the springs was a good
+medicine. They threw their blankets upon the water, and when these had
+become saturated with the oil, they wrung them out and sold the oil.
+Those were the times when if a medicine only tasted and smelled bad
+enough, people never doubted that it would cure all their diseases,
+and they gladly bought the oil of the Indians.
+
+When at last it became clear to the members of an enterprising company
+that oil for use in lamps could be made from petroleum, they secured
+some land in Pennsylvania that seemed promising and set to work to
+dig a well. But the more they dug, the more the loose dirt fell in
+upon them. Fortunately for the company, the superintendent had brains,
+and he thought out a way to get the better of the crumbling soil. He
+simply drove down an iron pipe to the sandstone which contained the
+oil, and set his borer at work within the pipe. One morning he found
+that the oil had gushed in nearly to the top of the well. He had
+"struck oil."
+
+This was about ten years after the rush to California for gold, and
+now that this cheaper and quicker method of making a well had been
+invented, there was almost as much of a rush to Pennsylvania for oil.
+With every penny that they could beg or borrow, people from the East
+hurried to the westward to buy or lease a piece of land in the hope of
+making their fortunes. A song of the day had for its refrain,--
+
+    "Stocks par, stocks up,
+      Then on the wane;
+    Everybody's troubled with
+      Oil on the brain."
+
+In the course of a year or two, the first "gusher" was discovered. The
+workmen had drilled down some four or five hundred feet and were
+working away peacefully, when a furious stream of oil burst forth
+which hurled the tools high up into the air. Hundreds of barrels
+gushed out every day, and soon other gushers were discovered. The most
+famous one in the world is at Lakeview, California. For months it
+produced fifty thousand barrels of oil a day, and threw it up three
+hundred and fifty feet into the air in a black column, spraying the
+country with oil for a mile around. The oil flowed away in a river,
+and for a time no one could plan any way to stop it or store it. At
+last, however, a mammoth tank was built around the well and made firm
+with stones and bags of earth. This was soon full of oil; and with all
+this vast weight of oil pressing down upon it, the stream could not
+rise more than a few feet above the surface. Just why oil should come
+out with such force, the geologists are not quite certain; but it is
+thought to result from a pressure of gas upon the sandstone containing
+it. The flow almost always becomes less and less, and after a time the
+most generous well has to be pumped.
+
+[Illustration: A CALIFORNIA OIL FIELD
+
+For scenery, one should not go to an oil field. Looks, smell, and oil
+alike are unpleasant, but every oil derrick covers a fortune and helps
+to make our machinery run smoothly.]
+
+An "oil field" may extend over thousands of square miles; but within
+this field there are always "pools"; that is, certain smaller fields,
+where oil is found. When a man thinks there is oil in a certain spot,
+sometimes he buys the land if he is able; but oftener he gets
+permission of the owner to bore a well, agreeing to pay him a royalty;
+that is, a certain percentage of all the oil that is produced. When
+this has been arranged, he builds his derrick. This consists of four
+strong upright beams firmly held together by crossbeams. It stands
+directly over the place where the well is to be dug. It is from thirty
+to eighty feet in height, according to the depth at which it is hoped
+to find oil. There must also be an engine house to provide the power
+for drilling. An iron pipe eight or ten inches in diameter is driven
+down through the soil until it comes to rock. Now the regular drilling
+begins. At the top of the derrick is a pulley. Over the pulley passes
+a stout rope to which the heavy drilling tools--the "string of tools,"
+as they are called--are fastened. The drilling goes on day and night.
+The drill makes the hole, and the sand pump sucks out the water and
+loose bits of stone. When the drill has gone to the bottom of the
+strata which carry water, the sides of the bore are cased to keep the
+water out; then the drilling continues, but now the drill makes its
+way into the oil-bearing sandstone.
+
+There is nothing certain about the search for oil. In some places it
+is near the surface, in others it is perhaps three or four thousand
+feet down. The well may prove to be a gusher and pour out hundreds of
+thousands of gallons a day; or the oil may refuse to rise to the
+surface and have to be pumped out even at the first. Naturally, no one
+is prepared for a gusher, and millions of gallons have often flowed
+away before any arrangements could be made for storing the oil.
+Sometimes a well that gives only a moderate flow can be made to yield
+generously by exploding a heavy charge of dynamite at the bottom, to
+break up the rock and, it is always hoped, to open some new
+oil-holding crevice that the drill has not reached.
+
+Crude petroleum is a dark, disagreeable, bad-smelling liquid; and
+before it can be of much use, it must be refined. For several years it
+was carried in barrels from the oil fields to Pittsburgh by wagon and
+boat, a slow, expensive process, and generally unsatisfactory to all
+but the teamsters. Then came the railroads. They provided iron tanks
+in the shape of a cylinder fastened to freight cars, much like those
+employed to-day. There was only one difficulty about sending oil by
+rail, and that was that it still had to be hauled by team to the
+railroad, sometimes a number of miles. At length, some one said to
+himself, "Why cannot we simply run a pipe directly from the well to
+the railroad?" This was done. Pumping engines were put in a few miles
+apart, and the invention was a success in the eyes of all but the
+teamsters. In spite of their opposition, however, pipe-lines
+increased.
+
+Before this it had been necessary to build the refineries as near the
+oil regions as possible in order to save the expense of carrying the
+oil; but now they could be built wherever it was most convenient.
+To-day oil can be brought at a small expense from west of the
+Mississippi River to the Atlantic seaboard, refined, and distributed
+throughout that part of the country, or loaded into "tankers,"--that
+is, steamships containing strong tanks of steel,--and so taken across
+the ocean. The pipes are made of iron and are six or eight inches or
+more in diameter. In using them one difficulty was found which has
+been overcome in an ingenious fashion. Sometimes they become choked by
+the impurities of the oil and the flow is lessened. Then a "go-devil"
+is put into them. This is shaped like a cartridge, is about three
+feet in length, composed of springs and plates of iron and so flexible
+that it can turn around a corner. It is so made that as it slips down
+the current of oil, it whirls around and in so doing its nose of sharp
+blades scrapes the pipes clean.
+
+The pipes go over hills and through swamps. They cross rivers
+sometimes by means of bridges, and sometimes they are anchored to the
+bed of the stream. If they have to go through a salt marsh, they are
+laid in concrete to preserve the iron. If these lines were suddenly
+destroyed and oil had to be carried in the old way, kerosene would
+become an expensive luxury.
+
+Getting the oil out of the ground and carried to the refineries is not
+all of the business by any means. The early oils crusted on the lamp
+wicks, their smell was unendurable, and they were given to exploding.
+Evidently, if oil was to be used for lighting, it must be improved,
+and the first step was to distil it. To distil anything means to boil
+it and collect the vapor. If you hold a piece of cold earthenware in
+the steam of a teakettle, water will collect on it. This is distilled
+water, and is purer than that in the kettle. Petroleum was at first
+distilled in a rough way; but now it is done with the utmost care and
+exactness. The crude oil is pumped into boilers holding six hundred
+barrels or more. The fires are started, and the oil soon begins to
+turn into vapor. This vapor passes through coils of pipe or long,
+straight, parallel pipes. Cold water is pumped over these pipes, the
+vapor turns into a liquid again, and we have kerosene oil.
+
+This is the outline of the process, but it is a small part of the
+actual work in all its details. Kerosene oil is only one of the many
+substances found in petroleum. Fortunately, some of these substances
+are light, like gasoline and benzine; some, like kerosene, are
+heavier; and paraffin and tar are heaviest of all. There are also
+gases, which pass off first and are saved to help keep the furnace
+going. Then come the others, one by one, according to their weight.
+The stillman keeps close watch, and when the color and appearance of
+the distillate changes, he turns it off into another tank. This
+process is called "fractional distillation," and the various products
+are called "fractions." No two kinds of petroleum and no two oil wells
+are just alike, and it needs a skillful man to manage either.
+
+Even after all this distillation, the kerosene still chars the wick
+somewhat--which prevents the wick from drawing up the oil
+properly--and it still has a disagreeable smell. To fit it for burning
+in lamps, it must be treated with sulphuric acid, which carries away
+some of the impurities, and then with caustic soda, which carries away
+others. Before it can be put on the market, it is examined to see
+whether it is of the proper color. Then come three important tests.
+The first is to see that it is of the proper weight. If it is too
+heavy, it will not burn freely enough; if it is too light, then there
+is too much of the lighter oils in it for safety. The second test is
+the "flash test." The object of this is to see how hot the oil must be
+before it gives off a vapor which will burn. The third, the "burning
+test," is to discover how hot the oil must be before it will take fire
+and burn on the surface. Most civilized countries make definite laws
+forbidding the sale of kerosene oil that is not up to a standard of
+safety. Oil for use in lamps should have an open flash test of at
+least 100° F. and a burning point of not less than 125° F.
+
+We say that we burn oil in our lamps, but what we really do is to heat
+the oil until it gives off gas, and then we burn the gas. To keep the
+flame regular and help on the burning, we use a chimney on the lamp.
+The hot air rises in the chimney and the cold air underneath rushes in
+to take its place and brings oxygen to the flame. In a close, stuffy
+room no lamp will give a good clear light, because there is not oxygen
+enough for its flame. Let in fresh air, and the light will be
+brighter. If you hold a cold plate in the flame before the chimney is
+put on, soot or carbon will be deposited. A lamp gives light because
+these particles of carbon become so hot that they glow. In lamps using
+a "mantle," there is the glow not only of these particles, but also of
+the mantle. In a wax candle, we light the wick, its heat melts the wax
+and carries it to the flame. When the wax is made hot enough, it
+becomes gas, and we burn the gas, not the wax. Wax alone will melt,
+but not take fire even if a burning match is held to it. The reason is
+that the match does not give heat enough to turn the wax into gas. But
+put a bit of wax upon a bed of burning coals, where there is a good
+supply of heat, and it will turn into gas and burn.
+
+The products made from petroleum are as different in their character
+and uses as paraffin and naphtha. Some of them are used for oiling
+machinery; tar is used for dyes; naphtha dissolves resin to use in
+varnish; benzine is the great cleanser of clothes, printers' types,
+and almost everything else; gasoline runs automobiles, motors, and
+many sorts of engines; paraffin makes candles, seals jelly glasses,
+covers the heads of matches so that they are no longer spoiled by
+being wet, and makes the ever-useful "waxed paper"; printers' ink and
+waterproof roofing-paper both owe a debt to petroleum. Even in
+medicine, though a little petroleum is no longer looked upon as a
+cure-all, vaseline, one of its products, is of great value. It can be
+mixed with drugs without changing their character, and it does not
+become rancid. For these reasons, salves and other ointments can be
+mixed with it and preserved for years.
+
+
+
+
+XI
+
+LITTLE GRAINS OF SALT
+
+
+The most interesting mine in the world is that of Wieliczka in Poland.
+In it there are some thirty miles of streets and alleys; there are
+churches with pillars, shrines, and statues; there are stairs,
+monuments, and restaurants; there is a ballroom three hundred feet
+long and one hundred and ninety feet high, with beautiful chandeliers,
+and in it is a carven throne whereon the Emperor Franz Joseph sat when
+he visited the mine. There are lakes crossed by ferryboats. There is a
+railroad station for the mule trains which bear the precious mineral
+salt, for this is a salt mine, and shrines, statues, churches,
+chandeliers--everything--are all cut out of salt.
+
+This mine has been worked for at least eight hundred years and still
+has salt enough to supply all Europe for ages. The mass of salt is
+believed to be five hundred miles long, fifty miles wide, and nearly a
+quarter of a mile thick. It is so pure that it is sold just as it
+comes from the mine, either in blocks or finely ground. This mine is a
+wonderful place to visit, almost like an enchanted palace, for as the
+torchlight strikes the crystals of salt, they flash and sparkle as if
+the wall was covered with rubies and diamonds.
+
+There is nothing like an enchanted palace in any salt mine of the
+United States, no statues or chapels or chandeliers. There is only a
+hole in the ground, where mining is carried on in much the same manner
+as in other kinds of mines. The shaft is sunk and lined with timbers
+to keep the dirt from falling in, just as in other mines. In working
+salt mines, however, water is almost as bad as earth, and therefore a
+layer of clay is put between the timbers and the earth. There are the
+usual galleries and pillars, with roof and floor of salt. The workmen
+try to get the salt out in lumps or blocks as far as possible, and so
+they bore in drill holes and then blast with dynamite or powder. The
+salt is loaded upon little cars, running on tracks, and is carried up
+the shaft and to the top of a breaker, usually more than one hundred
+feet above the surface of the ground. There it is dumped upon a screen
+of iron bars, which lets the fine salt fall through. The large lumps
+are sold without crushing or sifting, and are used for cattle and
+sheep.
+
+One of the great deposits of salt is in southeastern California. It is
+thought that the Gulf of California used to run much farther north
+than it now does, and that the earth rose, shutting away part of it
+from the ocean. This imprisoned water was full of salt. In time it
+dried, and the sand blew over it till it was far underground. A better
+way than digging was found to work it, as will be seen later; but
+while digging was going on, the workmen built a cottage of blocks of
+salt, clear and glassy. The little rain that falls there melted the
+blocks only enough to unite them firmly together; and there the house
+has stood for many years.
+
+Countries that have no deposits of rock salt can easily get plenty of
+salt from the water of the ocean if they only have a seacoast. About
+one thirtieth of the ocean water is salt, and if the water is
+evaporated, the salt can be collected without difficulty. France makes
+a great deal of salt in this way. When a man goes into the
+manufacture, or rather, the collecting of salt, he first of all buys
+or rents a piece of land,--perhaps several acres of it,--that lies
+just above high water, and makes it as level as possible. Unless it is
+very firm land, he covers it with clay, so that the water will not
+soak through it. Then he divides it into large square basins, making
+each a little lower than the one before it. Close beside the highest
+basin he makes a reservoir which at high tide receives water from the
+ocean. This flows slowly from the reservoir through one basin after
+another, becoming more and more salt as the water evaporates. At
+length the water is gone, and the salt remains. The workmen take
+wooden scrapers and push the salt toward the walls of the basins and
+then shovel it up on the dikes and heap it into creamy cones that
+sparkle in the sunshine. The dikes are narrow, raised pathways beside
+the basins and between them. As you walk along on top of them, you can
+smell a faint violet perfume from the salt. Thatch is put over the
+cones to protect them from the rain, and there they stand till some of
+the impurities drain away. This salt is not perfectly white, because
+the workmen cannot help scraping up a little of the gray or reddish
+clay with it. Most of it is sold as it is, nevertheless, for many
+people have an absurd notion that the darker it is the purer it is.
+For those who wish to buy white salt it is sent to a refinery to be
+washed with pure water, then boiled down and dried.
+
+So it is that the sun helps to manufacture salt. In some of the colder
+countries, frost does the same work, but in a very different manner.
+When salt water freezes, the _water_ freezes, but the salt does not,
+and a piece of salt water ice is almost as pure as that made of fresh
+water. Of course, after part of the water in a basin of salt water has
+been frozen out, what is left is more salt than it was at first, and
+after the freezing has been repeated several times, only a little
+water remains, and evaporation will soon carry this away, leaving only
+salt in the basin, waiting to be purified.
+
+Not very many years ago one of the encyclopædias remarked that "the
+deposits of salt in the United States are unimportant." This was true
+as far as the working of them was concerned, but in 1913 the United
+States produced more than 34,000,000 barrels. Part of this was made by
+evaporation of the waters of salt springs, and a small share from
+Great Salt Lake in Utah. The early settlers in Utah used to gather
+salt from the shallow bays or lagoons where the water evaporated
+during the summer; but now dams of earth hold back the water in a
+reservoir. In the spring the pumps are put to work and the reservoir
+is soon filled with water. This is left to stand and give the
+impurities a chance to settle to the bottom. Then it is allowed to
+flow into smaller basins, while more water is pumped into the
+reservoir. When autumn comes, the crop of salt is ready to be
+harvested. It is in the form of a crust three to six inches thick,
+some of it in large crystals, and some fine-grained. This crust is
+broken by ploughs, and the salt is heaped up into great cones and left
+for the rain to wash clean. Then it goes to the mill for purifying.
+The water of Great Salt Lake is much more salty than that of the
+ocean. It preserves timber remarkably well, and often salt from the
+lake is put around telephone poles, seventy-five pounds being dropped
+into the hole for each one. It has been suggested to soak timber in
+the Lake, and then paint it with creosote to keep the wet out and the
+salt in.
+
+Salt is also made from the waters of salt springs, which the Indians
+thought were the homes of evil spirits. At Salton, in California, an
+area of more than one thousand acres, which lies two hundred and
+sixty-four feet below sea level, is flooded with water from salt
+springs. When this water has evaporated, all these acres are covered
+with salt ten to twenty inches thick, and as dazzlingly white as if it
+was snow. This great field is ploughed up with a massive four-wheeled
+implement called a "salt-plough." It is run by steam and needs two men
+to manage it. The heavy steel ploughshare breaks up the salt crust,
+making broad, shallow furrows and throwing the salt in ridges on both
+sides. The plough has hardly moved on before the crust begins to form
+again. This broken crust is worked in water by men with hoes in order
+to remove the bits of earth that stick to it, then piled up into cones
+to drain, loaded upon flat trucks, and carried to the breaker. The
+salt fields are wonderfully beautiful in the moonlight, but not very
+agreeable to work in, for the mercury often reaches 140° F., and the
+air is so full of particles of salt that the workers feel an intense
+thirst, which the warm, brackish water does not satisfy. The work is
+done by Indians and Japanese, for white people cannot endure the heat.
+
+A large portion of the salt used in the United States comes directly
+from rock salt strata, hundreds of feet below the surface of the
+ground. These were perhaps the bed of the ocean ages and ages ago.
+There is a great extent of the beds in New York, Michigan, Ohio,
+Kansas, and other States. In Michigan there is a stratum of rock salt
+thirty to two hundred and fifty feet thick and some fifteen hundred to
+two thousand feet below the surface. To mine this would be a difficult
+and expensive undertaking, and a far better way has been discovered.
+First, a pipe is forced down through the surface dirt, the limestone,
+and the shale to the salt stratum. The drill works inside this pipe
+and bores a hole for a six-inch pipe directly into the salt. A
+three-inch pipe is let down inside of the six-inch pipe, and water is
+forced down through the smaller pipe. It dissolves the salt, becomes
+brine, and rises through the space between the two pipes. It is
+carried through troughs to some great tanks, and from these it flows
+into "grain-settlers," then into the "grainers" proper, where the
+grains of salt settle. At the bottom of the grainers are steam pipes,
+and these make the brine so hot that before long little crystals of
+salt are seen floating on the surface of the water. Crystals form much
+better if the water is perfectly smooth, and to bring this about a
+very little oil is poured into the grainer. It spreads over the
+surface in the thinnest film that can be imagined. The water
+evaporates, and the tiny crystals grow, one joining to another as they
+do in rock candy. When they become larger, they drop to the bottom of
+the grainer. They are now swept along in a trough to a "pocket,"
+carried up by an endless chain of buckets, and then wheeled away to
+the packinghouse.
+
+The finest salt is made by using vacuum pans. These are great cans out
+of which the air is pumped, and into which the brine flows. This
+brine, heated by steam pipes, begins to boil, and as the steam from it
+rises, it has to pass through a pipe at the top and is thus carried
+into a small tank into which cold water is flowing. The cold makes the
+steam condense into water, which runs off. The condensed water
+occupies less space than the steam and so maintains the vacuum in the
+pan. For a perfect vacuum the brine is boiled at less than 100° F.,
+while in an open pan or grainer it requires 226° to boil brine. The
+brine is soon so rich in salt that tiny crystals begin to form. These
+are taken out and dried. If you look at some grains of table salt
+through a magnifying glass, you can see that each grain is a tiny
+cubical crystal. Sometimes two or three are united, and often the
+corners are rounded off and worn, but they show plainly that they are
+little cubes.
+
+Most of the salt used on our tables is made by the vacuum process or
+by an improved method which produces tiny flakes of salt similar to
+snowflakes. The salt brine is heated to a high temperature and
+filtered. In the filters the impurities are taken out, and this
+process gives us very pure salt. The tiny flakes dissolve more easily
+than the cubes of salt, and thus flavor food more readily.
+
+With a few savage tribes salt is regarded as a great luxury, but with
+most peoples it is looked upon as a necessity. Some of the early races
+thought a salt spring was a special gift of the gods, and in their
+sacrifices they always used salt. In later times to sit "above the
+salt," between the great ornamental salt cellar and the master of the
+house, was a mark of honor. Less distinguished guests were seated
+"below the salt." To "eat a man's salt" and then be unfaithful to him
+has always been looked upon as a shameful act; and with some of the
+savages, so long as a stranger "ate his salt,"--that is, was a guest
+in the house of any one of them,--he was safe. To "eat salt together"
+is an expression of friendliness. Cakes of salt have been used as
+money in various parts of Africa and Asia. "Attic salt" means wit,
+because the Athenians, who lived in Attica, were famous for their
+keen, delicate wit. To take a story or a statement "with a grain of
+salt" means not to accept it entirely, but only to believe it
+partially. When Christ told his disciples that they were "the salt of
+the earth," he meant that their lives and teaching would influence
+others just as salt affects every article of food and changes its
+flavor. Our word "salary" comes from the Latin word _sal_, meaning
+salt; and _salarium_, or "salt-money," was money given for paying
+one's expenses on a journey. Living without salt would be a difficult
+matter. Cattle that have been shut away from it for a while are almost
+wild to get it. Farmers living among the mountains sometimes drive
+their cattle to a mountain pasture to remain there through the summer,
+and every little while they go up to salt the animals. The cattle know
+the call and know that it means salt; and I have seen them come
+rushing down the mountain-side and through the woods, over fallen
+trees, through briers, and down slippery rocks, bellowing as they
+came, and plunging head first in a wild frenzy to get to the pieces of
+rock salt that were waiting for them.
+
+       *       *       *       *       *
+
+
+
+
+FIRST YEAR IN NUMBER
+
+35 cents net. Postpaid
+
+An Introductory Book to Precede any Series of Arithmetics
+
+BY
+
+FRANKLIN S. HOYT
+
+_Formerly Assistant Superintendent of Schools, Indianapolis_
+
+AND
+
+HARRIET E. PEET
+
+_Instructor in Methods of Teaching Arithmetic, State Normal School,
+Salem, Massachusetts_
+
+The work is based upon the familiar experiences and activities of
+children, and follows as closely as possible the child's own method of
+acquiring new knowledge and skill.
+
+Thus we have lessons based on playing store, making tickets, mailing
+letters, fishing, etc. Every step is made interesting, but no time is
+wasted in mere entertainment.
+
+       *       *       *       *       *
+
+_By the same authors_
+
+THE EVERYDAY ARITHMETICS
+
+THREE-BOOK COURSE
+
+Book One, grades II-IV         $.40
+Book Two, grades V-VI           .40
+Book Three, grades VII-VIII     .45
+
+TWO-BOOK COURSE
+
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+Book Two, grades V-VIII.        .72
+
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+_Distinctive Features_
+
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+
+       *       *       *       *       *
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+HOUGHTON MIFFLIN COMPANY
+BOSTON     NEW YORK     CHICAGO
+1901
+
+
+
+
+"_A STEP FORWARD IN READING_"
+
+THE RIVERSIDE READERS
+
+EDITED BY
+
+JAMES H. VAN SICKLE
+
+_Superintendent of Schools, Springfield, Mass._
+
+AND
+
+WILHELMINA SEEGMILLER
+
+_Late Director of Art, Indianapolis. Formerly Principal of the Wealthy
+Avenue Public School, Grand Rapids, Mich._
+
+ASSISTED BY
+
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+
+_Instructor in Elementary Education, College for Teachers, University
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+HOUGHTON MIFFLIN COMPANY
+BOSTON     NEW YORK     CHICAGO
+1901
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+       *       *       *       *       *
+
+Transcriber's Notes
+
+The List of Illustrations was added, and some of the illustrations
+have been moved from their original positions to avoid breaking up
+paragraphs of text.
+
+
+
+
+
+
+
+
+End of Project Gutenberg's Diggers in the Earth, by Eva March Tappan
+
+*** END OF THIS PROJECT GUTENBERG EBOOK DIGGERS IN THE EARTH ***
+
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+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
+    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+
+<html xmlns="http://www.w3.org/1999/xhtml">
+  <head>
+    <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" />
+    <title>
+      The Project Gutenberg eBook of Diggers in the Earth, by Eva March Tappan.
+    </title>
+    <style type="text/css">
+/*<![CDATA[  XML blockout */
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+    p {  margin-top: .75em;
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+
+    table {margin-left: auto; margin-right: auto;}
+
+    body{margin-left: 10%;
+         margin-right: 10%;
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+
+    .pagenum  { /* uncomment the next line for invisible page numbers */
+            /*  visibility: hidden;  */
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+<body>
+
+
+<pre>
+
+The Project Gutenberg EBook of Diggers in the Earth, by Eva March Tappan
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Diggers in the Earth
+
+Author: Eva March Tappan
+
+Release Date: March 6, 2008 [EBook #24762]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK DIGGERS IN THE EARTH ***
+
+
+
+
+Produced by Diane Monico and The Online Distributed
+Proofreading Team at https://www.pgdp.net (This file was
+produced from images generously made available by The
+Internet Archive/American Libraries.)
+
+
+
+
+
+
+</pre>
+
+
+
+
+
+<h3>THE INDUSTRIAL READERS</h3>
+
+<h3><i>Book II</i></h3>
+
+<h1>DIGGERS IN THE<br />
+EARTH</h1>
+
+<h4>BY</h4>
+
+<h2>EVA MARCH TAPPAN, <span class="smcap">Ph</span>.D.</h2>
+
+<p class="center"><i>Author of "England's Story," "American Hero Stories,"<br />
+"Old World Hero Stories," "Story of the Greek People,"<br />
+"Story of the Roman People," etc. Editor of<br />
+"The Children's Hour."</i></p>
+
+<p class="figcenter" style="width: 99px;">
+<img src="images/image001.png" width="99" height="125" alt="" title="" />
+</p>
+
+<h4>HOUGHTON MIFFLIN COMPANY</h4>
+
+<h5>BOSTON&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;NEW YORK&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;CHICAGO</h5>
+<hr style="width: 65%;" />
+
+
+
+<p class="center"><b>THE INDUSTRIAL READERS</b></p>
+
+<p class="center"><b>By Eva March Tappan</b></p>
+
+
+
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" summary="readers">
+<tr><td align='right'>I.</td><td align='left'>THE FARMER AND HIS FRIENDS. 50 cents.</td></tr>
+<tr><td align='right'>II.</td><td align='left'> DIGGERS IN THE EARTH. 50 cents.</td></tr>
+<tr><td align='right'>III.</td><td align='left'> MAKERS OF MANY THINGS. 50 cents.</td></tr>
+<tr><td align='right'>IV.</td><td align='left'> TRAVELERS AND TRAVELING. 50 cents.</td></tr>
+</table></div>
+<p class="center">The foregoing are list prices, postpaid<br /><br /></p>
+
+
+<p class="center"><small>COPYRIGHT, 1916, BY EVA MARCH TAPPAN</small></p>
+<p class="center"><small>ALL RIGHTS RESERVED</small><br /><br /></p>
+
+<p class="center"><i>First printing April 1916;</i><br />
+<i>Reprinted December 1916</i><br /><br /><br /><br /></p>
+
+<p class="center">The Riverside Press<br />
+<small>CAMBRIDGE, MASSACHUSETTS</small><br />
+<small>U. S. A.</small>
+</p>
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_iii" id="Page_iii">[Pg iii]</a></span></p>
+
+
+<h2>PREFACE</h2>
+
+
+<p>The four books of this series have been written
+not merely to provide agreeable reading matter for
+children, but to give them information. When a
+child can look at a steel pen not simply as an article
+furnished by the city for his use, but rather as the
+result of many interesting processes, he has made a
+distinct growth in intelligence. When he has begun
+to apprehend the fruitfulness of the earth, both
+above ground and below, and the best way in which
+its products may be utilized and carried to the
+places where they are needed, he has not only acquired
+a knowledge of many kinds of industrial life
+which may help him to choose his life-work wisely
+from among them; but he has learned the dependence
+of one person upon other persons, of one part of
+the world upon other parts, and the necessity of
+peaceful intercourse. Best of all, he has learned to
+see. Wordsworth's familiar lines say of a man whose
+eyes had not been opened,&mdash;</p>
+
+<div class="poem"><div class="stanza">
+<span class="i0">"A primrose by a river's brim<br /></span>
+<span class="i0">A yellow primrose was to him,<br /></span>
+<span class="i0">And it was nothing more."<br /></span>
+</div></div>
+
+<p>These books are planned to show the children that
+there is "something more"; to broaden their horizon;
+to reveal to them what invention has accomplished
+and what wide room for invention still
+remains; to teach them that reward comes to the<span class='pagenum'><a name="Page_iv" id="Page_iv">[Pg iv]</a></span>
+man who improves his output beyond the task of the
+moment; and that success is waiting not for him who
+works because he must, but him who works because
+he may.</p>
+
+<p>Acknowledgment is due to the Lehigh Valley
+Railroad, Jones Brothers Company, Alpha Portland
+Cement Company, Dwight W. Woodbridge, the
+Utah Copper Company, the Aluminum Company
+of America, the Diamond Crystal Salt Company,
+T. W. Rickard, and others, whose advice and criticism
+have been of most valuable aid in the preparation
+of this volume.</p>
+
+<p class="author">
+Eva March Tappan.<br />
+</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_v" id="Page_v">[Pg v]</a></span></p>
+<h2><a name="CONTENTS" id="CONTENTS"></a>CONTENTS</h2>
+
+
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" width="50%" summary="toc">
+<tr><td align='right'>I.</td><td align='left'><span class="smcap">In a Coal Mine</span>  </td><td align='right'><a href="#Page_1">1</a></td></tr>
+<tr><td align='right'>II.</td><td align='left'><span class="smcap">Down in the Quarries</span></td><td align='right'>   <a href="#Page_11">11</a></td></tr>
+<tr><td align='right'>III.</td><td align='left'><span class="smcap">Houses of Sand</span></td><td align='right'>   <a href="#Page_21">21</a></td></tr>
+<tr><td align='right'>IV.</td><td align='left'><span class="smcap">Bricks, their Faults and their Virtues</span></td><td align='right'> <a href="#Page_31">31</a></td></tr>
+<tr><td align='right'>V.</td><td align='left'><span class="smcap">At the Gold Diggings</span></td><td align='right'>   <a href="#Page_39">39</a></td></tr>
+<tr><td align='right'>VI.</td><td align='left'><span class="smcap">The Story of a Silver Mine</span></td><td align='right'>  <a href="#Page_48">48</a></td></tr>
+<tr><td align='right'>VII.</td><td align='left'><span class="smcap">Iron, the Everyday Metal</span></td><td align='right'>  <a href="#Page_57">57</a></td></tr>
+<tr><td align='right'>VIII.</td><td align='left'><span class="smcap">Our Good Friend Copper</span></td><td align='right'><a href="#Page_65">65</a></td></tr>
+<tr><td align='right'>IX.</td><td align='left'><span class="smcap">The New Metal, Aluminum</span> </td><td align='right'><a href="#Page_76">76</a></td></tr>
+<tr><td align='right'>X.</td><td align='left'><span class="smcap">The Oil in our Lamps</span></td><td align='right'>   <a href="#Page_84">84</a></td></tr>
+<tr><td align='right'>XI.</td><td align='left'><span class="smcap">Little Grains of Salt</span>  </td><td align='right'><a href="#Page_95">95</a></td></tr>
+</table></div>
+
+
+
+<hr style="width: 45%;" />
+<h2>LIST OF ILLUSTRATIONS</h2>
+
+
+
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" width="50%" summary="loi">
+<tr><td align='left'>A STRUCTURAL STEEL APARTMENT BUILDING</td><td align='right'><a href="#Page_vi">vi</a></td></tr>
+<tr><td align='left'>HOW A COAL MINE LOOKS ABOVEGROUND</td><td align='right'><a href="#Page_5">5</a></td></tr>
+<tr><td align='left'>MINERS AND THEIR MINE</td><td align='right'><a href="#Page_10">10</a></td></tr>
+<tr><td align='left'>OPENING A GRANITE QUARRY</td><td align='right'><a href="#Page_13">13</a></td></tr>
+<tr><td align='left'>BUILDING A CONCRETE ROAD</td><td align='right'><a href="#Page_27">27</a></td></tr>
+<tr><td align='left'>IN A NEW JERSEY BRICK MILL</td><td align='right'><a href="#Page_33">33</a></td></tr>
+<tr><td align='left'>HYDRAULIC GOLD MINING</td><td align='right'><a href="#Page_41">41</a></td></tr>
+<tr><td align='left'>THE STORY OF A SPOON</td><td align='right'><a href="#Page_51">51</a></td></tr>
+<tr><td align='left'>IN THE STEEL FOUNDRY</td><td align='right'><a href="#Page_61">61</a></td></tr>
+<tr><td align='left'>IN A COPPER SMELTER</td><td align='right'><a href="#Page_67">67</a></td></tr>
+<tr><td align='left'>A "MOVIE" OF AN ALUMINUM FUNNEL</td><td align='right'><a href="#Page_79">79</a></td></tr>
+<tr><td align='left'>A CALIFORNIA OIL FIELD</td><td align='right'><a href="#Page_87">87</a></td></tr>
+</table></div>
+
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_vi" id="Page_vi">[Pg vi]</a></span></p>
+<p class="figcenter" style="width: 362px;">
+<img src="images/image006.jpg" width="362" height="580" alt="A STRUCTURAL STEEL APARTMENT BUILDING"
+ title="A STRUCTURAL STEEL APARTMENT BUILDING" />
+<span class="caption">A STRUCTURAL STEEL APARTMENT BUILDING<br /><br />
+
+<i><small>Courtesy American Bridge Co.</small></i><br /><br />
+
+First the steel frame, then the floors, then the stone or brick shell,
+then the interior finishing&mdash;this is how the building is made.</span>
+</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_1" id="Page_1">[Pg 1]</a></span></p>
+<h1><a name="THE_INDUSTRIAL_READERS" id="THE_INDUSTRIAL_READERS"></a>THE INDUSTRIAL READERS</h1>
+
+<h3>BOOK II</h3>
+
+<h2>DIGGERS IN THE EARTH</h2>
+
+
+
+<h2><a name="I" id="I"></a>I</h2>
+
+<h3>IN A COAL MINE</h3>
+
+
+<p>Did you ever wonder how beds of coal happened
+to be in the earth? This is their story.</p>
+
+<p>Centuries ago, so many thousand centuries that
+even the most learned men can only guess at their
+number, strange things were coming to pass. The
+air was so moist and cloudy that the sun's rays had
+hard work to get through. It was warm, nevertheless,
+for the crust of the earth was not nearly so
+thick as it is now, and much heat came from the
+earth itself. Many plants and trees grow best in
+warm, moist air; and such plants flourished in those
+days. Some of their descendants are living now, but
+they are dwarfs, while their ancestors were giants.
+There is a little "horse-tail" growing in our meadows,
+and there are ferns and club mosses almost everywhere.
+These are some of the descendants; but
+many of their ancestors were forty or fifty feet high.
+They grew very fast, especially in swamps; and when
+they died, there was no lack of others to take their
+places. Dead leaves fell and heaped up around them.<span class='pagenum'><a name="Page_2" id="Page_2">[Pg 2]</a></span>
+Stumps stood and decayed, just as they do in our
+forests to-day. Every year the soft, black, decaying
+mass grew deeper. As the crust of the earth was so
+thin, it bent and wrinkled easily. It often sank in
+one place and rose in another. When these low,
+swampy places sank, water rushed over them, pressing
+down upon them with a great weight and sweeping
+in sand and clay. Now, if you burn a heap of
+wood in the open air, the carbon in the wood burns
+and only a pile of ashes remains. "Burning" means
+that the carbon in the wood unites with the oxygen
+gas in the air. If you cover the wood before you
+light it, so that only a little oxygen reaches it, much
+of the carbon is left, in the form of charcoal.</p>
+
+<p>When wood decays, its carbon unites with the
+oxygen of the air; and so decay is really a sort of
+burning. In the forests of to-day the leaves, and at
+length the trees themselves, fall and decay in the
+open air; but at the time when our coal was forming,
+the water kept the air away, and much carbon was
+left. This is the way coal was made. Some of the
+layers, or strata, are fifty or sixty feet thick, and
+some are hardly thicker than paper. On top of each
+one is a stratum of sandstone or dark-gray shale.
+This was made by the sand and mud which were
+brought in by the water. These shaly rocks split
+easily into sheets and show beautiful fossil impressions
+of ferns. There are also impressions of the
+bark and fruit of trees, together with shells, crinoids,
+corals, remains of fishes and flying lizards, and some
+few trilobites,&mdash;crablike animals with a shell somewhat<span class='pagenum'><a name="Page_3" id="Page_3">[Pg 3]</a></span>
+like the back of a lobster, but marked into
+three divisions or lobes, from which its name comes.</p>
+
+<p>Since the crust of the earth was so thin and yielding,
+it wrinkled up as the earth cooled, much as the
+skin of an apple wrinkles when the apple dries. This
+brought some of the strata of coal to the surface,
+and after a while people discovered that it would
+burn. If a vein of coal cropped out on a man's farm,
+he broke some of it up with his pickaxe, shoveled it
+into his wheelbarrow, and wheeled it home. After
+a while hundreds of thousands of people wanted
+coal; and now it had to be mined. In some places
+the coal stratum was horizontal and cropped out on
+the side of a hill, so that a level road could be dug
+straight into it. In other places the coal was so near
+the surface that it could be quarried under the open
+sky, just as granite is quarried. Generally, however,
+if you wish to visit a coal mine, you go to a shaft, a
+square, black well sometimes deeper than the height
+of three or four ordinary church steeples. You get
+into the "cage," a great steel box, and are lowered
+down, down, down. At last the cage stops and you
+are at the bottom of the mine. The miners' faces,
+hands, overalls, are all black with coal dust. They
+wear tiny lamps on their caps, and as they come
+near the walls of coal, it sparkles as it catches the
+light. Here and there hangs an electric lamp. It is
+doing its best to give out light, but its glass is thick
+with coal dust. The low roof is held up by stout
+wooden timbers and pillars of coal. A long passageway
+stretches off into a blacker darkness than you<span class='pagenum'><a name="Page_4" id="Page_4">[Pg 4]</a></span>
+ever dreamed of. Suddenly there is a blaze of red
+light far down the passage, a roar, a medley of all
+sorts of noises,&mdash;the rattling of chains, the clattering
+of couplings, the shouts of men, the crash of coal
+falling into the bins. It is a locomotive dragging its
+line of cars loaded with coal. In a few minutes it
+rushes back with empty cars to have them refilled.</p>
+
+<p>All along this passageway are "rooms," that is,
+chambers which have been made by digging out the
+coal. Above them is a vast amount of earth and
+rock, sometimes hundreds of feet in thickness. There
+is always danger that the roof will cave in, and so
+the rooms are not made large, and great pillars of
+coal are left to hold up the roof.</p>
+
+<p>Not many years ago the miner used to do all the
+work with his muscles; now machines do most of it.
+The miner then had to lie down on his side near the
+wall of coal in his "room" and cut into it, close to
+the floor, as far as his pickaxe would reach. Then
+he bored a hole into the top of the coal, pushed in a
+cartridge, thrust in a slender squib, lighted it, and
+ran for his life. The cartridge exploded, and perhaps
+a ton or two of coal fell. The miner's helper shoveled
+this into a car and pushed it out of the room to join
+the long string of cars.</p>
+<p><span class='pagenum'><a name="Page_5" id="Page_5">[Pg 5]</a></span></p>
+<p class="figcenter" style="width: 600px;">
+<img src="images/image011.jpg" width="600" height="310" alt="HOW A COAL MINE LOOKS ABOVEGROUND" title="HOW A COAL MINE LOOKS ABOVEGROUND" />
+<span class="caption">HOW A COAL MINE LOOKS ABOVEGROUND<br /><br />
+
+All that shows on the surface is the machinery shed where
+the various engines work to keep the air fresh, and bring
+up the miners and the coal.</span>
+</p>
+
+<p>That is the way mining used to be done. In these
+days a man with a small machine for cutting coal
+comes first. He puts his cutter on the floor against
+the wall of coal and turns on the electricity. <i>Chip,
+chip</i>, grinds the machine, eating its way swiftly into
+the coal, and soon there is a deep cut all along the<span class='pagenum'><a name="Page_6" id="Page_6">[Pg 6]</a></span>
+side of the room. The man and his machine go elsewhere,
+and the first room is left for its next visitors.
+They come in the evening and bore holes for the
+blasting. Once these holes were bored by hand, but
+now they are made with powerful drills that work
+by compressed air. A little later other men come
+and set off cartridges. In the morning when the
+dust has settled and the smoke has blown away, the
+loaders appear with their shovels and load the coal
+into the cars. Then it is raised to the surface and
+made ready for market.</p>
+
+<p>Did you ever notice that some pieces of coal are
+dull and smutty, while others are hard and bright?
+The dull coal is called bituminous, because it contains
+more bitumen or mineral pitch. This is often
+sold as "run-of-mine" coal,&mdash;that is, just as it
+comes from the mine, whether in big pieces or in
+little ones; but sometimes it is passed over screens,
+and in this process the dust and smaller bits drop
+out.</p>
+
+<p>The second kind of coal, the sort that is hard and
+bright, is anthracite. Its name is connected with a
+Greek word meaning ruby. It burns with a glow,
+but does not blaze. Most of the anthracite coal is
+used in houses, and householders will not buy it
+unless the pieces are of nearly the same size and free
+from dirt, coal dust, and slate. The work of preparation
+is done in odd-shaped buildings called "breakers."
+One part of a breaker is often a hundred or a
+hundred and fifty feet in height. The coal is carried
+to the top of the breaker. From there it makes a<span class='pagenum'><a name="Page_7" id="Page_7">[Pg 7]</a></span>
+journey to the ground, but something happens to it
+every little way. It goes between rollers, which
+crush it; then over screens, through which the
+smaller pieces fall. Sometimes the screens are so
+made that the coal will pass over them, while the
+thin, flat pieces of slate will fall through. In spite
+of all this, bits of coal mixed with slate sometimes
+slide down with the coal, and these are picked out
+by boys. A better way of getting rid of them is now
+coming into use. This is to put the coal and slate
+into moving water. The slate is heavier than the
+coal, and sinks; and so the coal can easily be separated
+from it. Dealers have names for the various
+sizes of coal. "Egg" must be between two and two
+and five eighths inches in diameter; "nut" between
+three fourths and one and one eighth inches; "pea"
+between one half and three fourths of an inch.</p>
+
+<p>Mining coal is dangerous work. Any blow of the
+pickaxe may break into a vein of water which will
+burst out and flood the mine. The wooden props
+which support the roof may break, or the pillars of
+coal may not be large enough; and the roof may fall
+in and crush the workers. There are always poisonous
+gases. The coal, as has been said before, was
+made under water, and therefore the gas which was
+formed in the decaying leaves and wood could not
+escape. It is always bubbling out from the coal, and
+at any moment a pickaxe may break into a hole that
+is full of it. One kind of gas is called "choke-damp,"
+because it chokes or suffocates any one who breathes
+it. There is also "white-damp," the gas which you<span class='pagenum'><a name="Page_8" id="Page_8">[Pg 8]</a></span>
+see burning with a pretty blue flame over a hot coal
+fire. Worst of all is the "fire-damp." If you stir up
+the water in a marsh, you will see bubbles of it rise
+to the surface. It is harmless in a marsh, but quite
+the opposite in a mine. When it unites with a certain
+amount of air, it becomes explosive, and the
+least bit of flame will cause a terrible explosion.
+Even coal dust may explode if the air is full of it,
+and it is suddenly set in motion by too heavy a blast
+of powder.</p>
+
+<p>Miners used to work by candlelight. Every one
+knew how dangerous this was; but no one found any
+better way until, about a hundred years ago, Sir
+Humphry Davy noticed something which other
+people had not observed. He discovered that flame
+would not pass through fine wire gauze, and he made
+a safety lamp in which a little oil lamp was placed
+in a round funnel of wire gauze. The light, but not
+the flame, would pass through it; and all safety
+lamps that burn oil have been made on this principle.
+The electric lamp, however, is now in general
+use. The miner wears it on his cap, and between his
+shoulders he carries a small, light storage battery.
+Even with safety lamps, however, there are sometimes
+explosions. The only way to make a mine at
+all safe from dangerous gases is to keep it full of
+fresh, pure air. There is no wind to blow through
+the chambers and passages, and therefore air has
+to be forced in. One way is to keep a large fire at
+the bottom of the air shaft. If you stand on a stepladder,
+you will feel that the top of the room is much<span class='pagenum'><a name="Page_9" id="Page_9">[Pg 9]</a></span>
+warmer than the floor. This is because hot air rises;
+and in a mine, the hot air over the fire rises and sucks
+the foul air and gas out of the mine, and fresh air
+rushes in to take its place. Another way is by a
+"fan," a machine that forces fresh air into the
+mine.</p>
+<p><span class='pagenum'><a name="Page_10" id="Page_10">[Pg 10]</a></span></p>
+<p class="figcenter" style="width: 390px;">
+<img src="images/image015.jpg" width="390" height="600" alt="MINERS AND THEIR MINE"
+ title="MINERS AND THEIR MINE" />
+<span class="caption">MINERS AND THEIR MINE<br /><br />
+
+Notice the safety lamps in the men&#39;s caps, and the little railroad
+on which the cars of coal and ore travel, hauled by the useful mule.</span>
+</p>
+
+<p>So it is that by hard work and much danger we
+get coal for burning. Now, coal is dirty and heavy.
+A coal fire is hard to kindle and hard to put out, and
+the ashes are decidedly disagreeable to handle. And
+after all, we do not really burn the coal itself, but
+only the gas from it which results from the union of
+carbon and oxygen. In some places natural gas, as
+it is called, which comes directly from some storehouse
+in the ground, is used in stoves and furnaces
+and fireplaces for both heating and cooking; and
+perhaps before long gas will be manufactured so
+cheaply and can be used so safely and comfortably
+that we shall not have to burn coal at all, but can
+use gas for all purposes&mdash;unless electricity should
+take its place.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_11" id="Page_11">[Pg 11]</a></span></p>
+<h2><a name="II" id="II"></a>II</h2>
+
+<h3>DOWN IN THE QUARRIES</h3>
+
+
+<p>When walking in the country one day I came to a
+beautiful pond by the side of the road. The water
+was almost as clear as air, and as I looked down into
+it, I could see that the bottom was made of granite.
+The farther shores were cliffs of clean granite thirty
+or forty feet high and coming down to the water's
+edge. The marks of tools could be seen on them,
+showing where blocks of stone had evidently been
+split off. I picked up a piece of the rock and examined
+it closely. It proved to be made up of three
+kinds of material. First, there were tiny sparkling
+bits of mica. In some places there are mica mines
+yielding big sheets of this curious mineral which
+is used in the doors of stoves and the little windows
+of automobile curtains. With the point of a knife
+the bits in my piece of granite could be split into
+tiny sheets as thin as paper. The second material
+was quartz. This was grayish-white and looked
+somewhat like glass. The third material was feldspar.
+This, too, was whitish, but one or two sides
+of each bit were flat, as if they had not been broken,
+but split. This is the most common kind of granite.
+There are many varieties. Some of them are almost
+white, some dark gray, others pale pink, and yet
+others deep red. It is found in more than half the
+States of the Union.<span class='pagenum'><a name="Page_12" id="Page_12">[Pg 12]</a></span></p>
+
+<p>This quarry had been given up and allowed to fill
+with water; but it was a granite country, and farther
+down the road there was another, where scores of
+men were hard at work. This second quarry was
+part-way up a hill; or rather, it was a hill of granite
+which men were digging out and carrying away.
+When they began to open the quarry, much of the
+rock was covered with dirt and loose stones, and
+even the granite that showed aboveground was worn
+and broken and stained. This is called "trap rock."
+The easiest way to get rid of it is to blast with dynamite
+and then carry away the dirt and fragments.
+Next comes the getting out of great masses of rock
+to use, some of them perhaps long enough to make
+the pillars of a large building.</p>
+<p><span class='pagenum'><a name="Page_13" id="Page_13">[Pg 13]</a></span></p>
+<p class="figcenter" style="width: 369px;">
+<img src="images/image019.jpg" width="369" height="580" alt="OPENING A GRANITE QUARRY"
+ title="OPENING A GRANITE QUARRY" />
+<span class="caption">OPENING A GRANITE QUARRY<br /><br />
+
+<i><small>Courtesy Jones Brothers Company.</small></i><br /><br />
+
+The first thing to do is to strip off the soil from the stone. Then,
+as the blocks are cut out, the big derrick lifts and loads them on
+waiting cars.</span>
+</p>
+
+<p>Now, granite is a hard stone, but there is no
+special difficulty in cutting it if you know how. In
+the old days, when people wished to split a big
+boulder, they sometimes built a fire beside it, and
+when it was well heated, they dropped a heavy iron
+ball upon it. King's Chapel in Boston was built
+of stone broken in this way. To break from a cliff,
+however, a block of granite big enough to make a
+long pillar is a different matter, and this is what the
+men were doing. First of all, the foreman had examined
+the quarry till he had found a stratum of the
+right thickness. He had marked where the ends
+were to come, and the men had drilled holes down
+to the bottom of the stratum. Then he had drawn
+a line at the back along where he wished the split to
+be, and the men had drilled on this line also a row<span class='pagenum'><a name="Page_14" id="Page_14">[Pg 14]</a></span>
+of holes. Next came the blasting. If one very heavy
+charge had been exploded, it would probably have
+shattered the whole mass, or at any rate have injured
+it badly. Instead of this, they put into each
+hole a light charge of coarse powder and covered it
+with sand. These were all fired at the same instant,
+and thus the great block was loosened from the wall.
+Sometimes there seems to be no sign of strata, and
+then a line of horizontal holes must be drilled where
+the bottom of the block is to be. After this comes
+what is called the "plug-and-feather" process. Into
+each hole are placed two pieces of iron, shaped like
+a pencil split down the middle. These are the
+"feathers." The "plug" is a small steel wedge that
+is put between the iron pieces. Then two men with
+hammers go down the line and strike each wedge
+almost as gently as if it was a nut whose kernel they
+were afraid of crushing. They go down the line
+again, striking as softly as before. Then, if you look
+closely, you can see a tiny crack between the holes.
+There is more hammering, the crack stretches farther,
+a few of the wedges are driven deeper and the
+others drop out. The block splits off. A mighty
+chain is then wound about it, the steam derrick lifts
+it, lays it gently upon a car, and it is carried to the
+shed to be cut into shape, smoothed, and perhaps
+polished.</p>
+
+<p>In almost every kind of work new methods are
+invented after a while. In quarrying, however, the
+same old methods are in use. The only difference is
+that, instead of the work being done by muscle, it is<span class='pagenum'><a name="Page_15" id="Page_15">[Pg 15]</a></span>
+done by compressed air or steam or electricity. Compressed
+air or steam works the drill and the sledgehammer.
+The drill is held by an arm, but the arm is
+a long steel rod which is only guided by the workman.
+Not the horse-sweep of old times, but the
+steam derrick and the electric hoist lift the heavy
+blocks from the quarry. Polishing used to be a very
+slow, expensive operation, because it was all done
+by the strength of some one's right arm, but now,
+although it takes as much work as ever, this work is
+done by machinery. To "point" a piece of stone,
+or give it a somewhat smooth surface, is done now
+with tools worked by compressed air. After this,
+the stone is rubbed&mdash;by machinery, of course&mdash;with
+water and emery, then by wet felt covered with
+pumice or polishing putty. A few years ago two
+young Vermonters invented a machine that would
+saw granite. This saw has no teeth, but only blades
+of iron. Between these blades and the piece of granite,
+however, shot of chilled steel are poured; and
+they do the real cutting.</p>
+
+<p>Granite has long been used in building wherever
+a strong, solid material was needed; but until the
+sand blast was tried, people thought it impossible
+to do fine work in this stone. There was a firm in
+Vermont, however, who believed in the sand blast.
+They had a contract with the Government to furnish
+several thousand headstones for national cemeteries.
+Cutting the names would be slow and costly;
+so they made letters and figures of iron, stuck them
+to the stones, and turned on the blast. If a sand<span class='pagenum'><a name="Page_16" id="Page_16">[Pg 16]</a></span>
+blast is only fast enough, it will cut stone harder
+than itself. The blast was turned upon a stone for
+five minutes. Then the iron letters were removed.
+There stood in raised letters the name, company,
+regiment, and rank of the soldier, while a quarter of
+an inch of the rest of the stone, which the iron letters
+had not protected, had been cut away. By means of
+the sand blast it has become possible to do beautiful
+carving even in material as hard as granite.</p>
+
+<p>Granite looks so solid that people used to think it
+was fireproof; but it is really poor material in a great
+fire. Most substances expand when they are heated;
+but the three substances of which granite is made do
+not expand alike, and so they tend to break apart
+and the granite crumbles.</p>
+
+<p>A marble quarry is even more interesting than a
+granite quarry. If you stand on a hill in a part of
+the country where marble is worked, you will see
+white ledges cropping out here and there. The little
+villages are white because many of the houses are
+built of marble. Then, too, there are great marble
+quarries flashing in the sunshine. Sometimes a
+marble quarry is chiefly on the surface. Sometimes
+the marble stretches into the earth, and the cutting
+follows it until a great cavern is made, perhaps two
+or three hundred feet deep. A roof is often built to
+keep out the rain and snow. It keeps out the light,
+too, and on rainy days the roof, together with the
+smoke and steam of the engines, makes the bottom
+of the quarry a gloomy place. Everywhere there are
+slender ladders with men running up and down<span class='pagenum'><a name="Page_17" id="Page_17">[Pg 17]</a></span>
+them. There are shouts of the men, clanking of
+chains, and puffing of locomotives.</p>
+
+<p>Marble is cut out in somewhat the same way as
+granite, but a valuable machine called a "channeler"
+is much used. This machine runs back and
+forth, cutting a channel two inches wide along the
+ends and back and sometimes the bottom of the
+block to be taken out.</p>
+
+<p>Marble is so much softer than granite that it is
+far more easy to work. Cutting it is a simple matter.
+The saw, which is a smooth flat blade of iron, swings
+back and forth, while between it and the marble
+sand and water are fed. It does not exactly <i>cut</i>, but
+rubs, its way through. The round holes in the tops
+of washstands are cut by saws like this, only bent
+in the form of a cylinder and turned round and
+round, going in a little deeper at each revolution.
+A queer sort of saw is coming into use. It is a cord
+made of three steel wires twisted loosely together.
+This cord is stretched tightly over pulleys and
+moves very rapidly. Every little ridge of the cord
+strikes the stone and cuts a little of it away.</p>
+
+<p>There are varieties of marble without end. The
+purest and daintiest is the white of which statues
+are carved; but there are black, red, yellow, gray,
+blue, green, pink, and orange in all shades. Many
+are beautifully marked. The inner walls of buildings
+are sometimes covered with thin slabs of marble.
+These are often carefully split, and the two pieces
+put up side by side, so that the pattern on one is
+reversed on the other. Certain kinds of marble contain<span class='pagenum'><a name="Page_18" id="Page_18">[Pg 18]</a></span>
+fossils or remains of coral and other animals
+that lived hundreds of thousands of years ago. In
+some marbles there are so many that the stone seems
+to be almost made of them. When a slab is cut and
+polished, the fossils are of course cut into; but even
+then we can sometimes see their shape. One of the
+most common is the crinoid. This was really an
+animal, but it looked somewhat like a closed pond
+lily with a long stem, and people used to call it the
+stone lily. This stem is made up of little flat rings
+looking like bits of a pipestem. The stems are often
+broken up and these bits are scattered through the
+marble. The animals whose shells help to make
+marble lived in the ocean, and when they died sank
+to the bottom. Many of the shells were broken by
+the beating of the waves, but both broken shells and
+whole ones became united and hardened into limestone,
+one kind of which we call marble. Common
+chalk is another kind. Blackboard crayons are made
+of this: so are whitewash and whiting for cleaning
+silver and making putty.</p>
+
+<p>Another stone that builders would be sorry to do
+without is slate. This, too, was formed at the bottom
+of the sea. Rivers brought down fine particles
+of clay, which settled, were covered by other matter,
+and finally became stone. It was formed in layers,
+of course, but, queerly enough, it splits at right
+angles to its bottom line. Just why it does this is
+not quite certain, but the action is thought to be
+due to heat and long, slow pressure, which will do
+wonderful things, as in the case of coal. This splitting<span class='pagenum'><a name="Page_19" id="Page_19">[Pg 19]</a></span>
+is a great convenience for the people who want
+to use it for roofing and for blackboards. Blocks of
+slate are loosened by blasting, and are taken to the
+splitting-shed.</p>
+
+<p>Splitting slate needs care, and a man who is not
+careful should never try to work in a slate quarry.
+The splitting begins by one man's dividing the
+block into pieces about two inches thick and somewhat
+larger than the slates are to be when finished.
+The way he does this is to cut a little notch in one
+end of the block with his "sculpin chisel" and make
+a groove from this across the block. He must then
+set his chisel into the groove, strike it with a mallet,
+and split the slate to the bottom. This sounds easy,
+but it needs skill. Slate has sometimes its own notions
+of behavior, and it does not always care to
+split in a straight line exactly perpendicular to the
+bottom of the stratum. The man keeps it wet so
+that he can see the crack more plainly, and if that
+crack turns back a little to the right, he must turn
+it to the left by striking the sculpin toward the left,
+or perhaps by striking a rather heavy blow on the
+left of the stone itself. Now the chief splitter takes
+it, and with a broad thin chisel he splits it into plates
+becoming thinner at each split. The second assistant
+trims these into the proper shape and size with
+either a heavy knife or a machine. Slate can be
+sawed and planed; but whatever is done to it should
+be done when it first comes from the quarry, for
+then it is not so likely to break. It would be very
+much cheaper if so much was not broken and wasted<span class='pagenum'><a name="Page_20" id="Page_20">[Pg 20]</a></span>
+at the quarries and in the splitting. It is said that
+in Wales sometimes one hundred tons of stone are
+broken up to get between three and four tons of
+good slate. Within the last few years the quarrymen
+have been using channeling machines and getting
+out the slate in great masses instead of small blocks.
+This is not so wasteful by any means; but even now
+there is room for new and helpful inventions.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_21" id="Page_21">[Pg 21]</a></span></p>
+<h2><a name="III" id="III"></a>III</h2>
+
+<h3>HOUSES OF SAND</h3>
+
+
+<p>If you wanted to build a house, of what should
+you build it? In a new country, people generally
+use wood; but after a time wood grows expensive.
+Moreover, wood catches fire easily; therefore, as a
+country becomes more thickly settled and people
+live close together in cities, stone and brick are used.
+Large cities do not allow the building of wooden
+houses within a certain distance from the center,
+and sometimes even the use of wooden shingles is
+forbidden. Of late years large numbers of "concrete"
+or "cement" houses have been built. Our
+grandfathers would have opened their eyes wide at
+the suggestion of a house built of sand, and would
+have felt anxious at every rainfall lest their homes
+should suddenly melt away. Even after thousands
+of concrete buildings were in use, many people still
+feared that they would not stand the cold winters
+and hot summers of the United States; but it has
+been proved that concrete is a success provided it is
+properly made.</p>
+
+<p>No one can succeed in any work unless he understands
+how it should be done. Concrete is made of
+Portland cement, mixed with sand and water and
+either broken stone, gravel, cinders, or slag; but if
+any one thinks that he can mix these together without
+knowing how and produce good concrete, he<span class='pagenum'><a name="Page_22" id="Page_22">[Pg 22]</a></span>
+will make a bad mistake rather than a good building
+material.</p>
+
+<p>First, he must buy Portland cement of the best
+quality. This cement is made of limestone and clay,
+or marl, chalk, and slag. These are crushed and
+ground and put into a kiln which is heated up to
+2500&deg; or 3000&deg;F.; that is, from twelve to fourteen
+times as hot as boiling water. The stone fuses sufficiently
+to form a sort of clinker. After this has
+cooled, it is ground so fine that the greater part of it
+will pass through a sieve having 40,000 meshes to
+the square inch. To every hundred pounds of this
+powder, about three pounds of gypsum is added.
+The mixture is then put into the bags in which we
+see it for sale in the stores. This powder is so greedy
+for water that it will absorb the moisture from the
+air around it. Even in the bags, it begins to harden
+as soon as it gets some moisture; and as soon as it
+hardens, it is of no use. The moral of that is to keep
+your cement in a dry place.</p>
+
+<p>The second substance needed in concrete is broken
+stone or gravel. Of course a hard rock must be selected,
+such as granite or trap rock. Limestone
+calcines in a heat exceeding 1000&deg; F., and therefore
+it cannot be used in fireproof construction. Soft
+rock, like slate or shale or soft sandstone, will not
+answer because it is not strong enough. Gravel is
+always hard. If you look at a cut in a gravel bank,
+you will usually see strata of sand and then strata
+of rounded pebbles of different sizes. The sand was
+once an ancient sea beach; the pebbles were dashed<span class='pagenum'><a name="Page_23" id="Page_23">[Pg 23]</a></span>
+up on it by waves or storms or some change of currents.
+They were at first only broken bits of rock,
+but after being rolled about for a few thousand years
+in the ocean and on the shore, the corners were all
+rounded. Soft rock would have been ground to
+powder by such treatment. Sometimes, if there is
+to be no great strain on the concrete, cinders or
+pieces of brick may be used instead of stone; and
+for some purposes they answer very well.</p>
+
+<p>The third substance used in concrete is sand; but
+it must be the right kind of sand, having both fine
+and coarse grains. These grains need to be sharp, or
+the cement will not stick to them well. They must
+also be clean, that is, free from dirt. If you rub sand
+between your hands, and it soils them, then there
+is clay or loam with it, and it must not be used in
+making concrete unless it is thoroughly washed.
+Another way of testing it is to put it into a glass
+jar partly full of water and shake it. Then let it
+settle. If there is soil in the sand, it will appear as a
+stratum of mud on top of the sand.</p>
+
+<p>The water with which these three substances are
+to be mixed must be clean and must contain no acid
+and no strong alkali. As a general rule, there must
+be twice as much broken stone as sand. When people
+first make concrete, they often expect too much
+of their materials. A good rule for the strongest sort
+of cement, strong enough for floors on which heavy
+machines are to stand, is one fourth of a barrel of
+cement, half a barrel of sand, and one barrel of
+gravel or broken stone. Apparently this would make<span class='pagenum'><a name="Page_24" id="Page_24">[Pg 24]</a></span>
+one and three fourths barrels; but in reality it makes
+only about one barrel, because the sand fills in the
+spaces between the gravel, and the cement fills in
+the spaces between the grains of sand.</p>
+
+<p>There are many sorts of machines on the market
+for mixing the materials; but small quantities can
+just as well be mixed by hand. The "mixing-bowl"
+is a platform, and on this the sand is laid. Then
+comes the cement; and these two must be shoveled
+together several times. While this is being done,
+the broken stone or gravel must be wet, and now it
+is put on top of the sand and cement and well shoveled
+together, with just enough water added so that
+the mass will almost bear the weight of a man.</p>
+
+<p>Concrete is impatient to be hardening, and if it
+is not put into the right place, it will begin promptly
+to harden in the wrong place, and nothing can be
+done with it afterwards. If it is to be made in
+blocks, the moulds must be ready and the concrete
+put into them at once and well tamped down. For
+such uses as beams and the sides of tanks where
+great strength is needed, the cement is often "reinforced,"
+that is, rods of iron or steel are embedded
+in it. For floors, a sheet of woven wire is often
+stretched out and embedded. At first only solid
+blocks, made to imitate rough stone, were used for
+houses, but the hollow block soon took their place.
+This is cheaper; houses built this way are warmer
+in winter and cooler in summer; and it prevents
+moisture from working through the walls. Many
+cities have regulations about the use of hollow<span class='pagenum'><a name="Page_25" id="Page_25">[Pg 25]</a></span>
+blocks, all the more strict because concrete is comparatively
+new as a building material. In Philadelphia
+the blocks must be composed of at least one
+barrel of Portland cement to five barrels of crushed
+rock or gravel. They must be three weeks old or
+more before being used; the lintels and sills of the
+doors must be reinforced; and every block must be
+marked, so that if the building should not prove to
+be of proper strength, the maker may be known.
+There would seem, however, to be little question of
+the quality of the blocks, for samples must pass the
+tests of the Bureau of Building Inspection.</p>
+
+<p>Even better than the hollow block is the method of
+making the four walls of a house at once by building
+double walls of boards and pouring in the concrete.
+When this has hardened, the boards are removed,
+and whatever sort of finish the owner prefers is
+given to the walls. They can be treated by spatter-work,
+pebble dash, or in other ways before the
+cement is fully set, or by bush hammering and tool
+work after the cement has hardened. Coloring
+matter can be mixed with the cement in the first
+place; and if the owner decides to change the color
+after the house is completed, he can paint it with
+a thin cement of coloring matter mixed with plaster
+of Paris.</p>
+
+<p>A concrete house has several advantages. In the
+first place, it will not burn. Neither will granite, but
+granite will fall to pieces in a hot fire. Granite is
+made of quartz, mica, and feldspar, as has been said
+before. These three do not expand alike in heat;<span class='pagenum'><a name="Page_26" id="Page_26">[Pg 26]</a></span>
+and therefore great flakes of the stone split off, so
+that it really seems to melt away. A well-made
+concrete is not affected by fire. It will not burn, and
+it will not carry heat to make other things burn.
+For a concrete house no paint is needed and less
+fuel will be required to keep it warm. If the floors
+are made with even a very little slant, "house-cleaning"
+consists of removing the furniture and
+turning on the hose. Water-tank, sink, washtubs,
+and bathtubs can be cast in concrete and given a
+smooth finish. Wooden floors can be laid over the
+concrete, or a border of wood can be put around
+each room for tacking down carpets or rugs. A concrete
+house may be as ornamental as the owner
+chooses, for columns and cornices and mouldings
+can easily be made of concrete; and if they are cast
+in sand, as iron is, they will have a finish like sandstone.</p>
+
+<p>It is somewhat troublesome to lay concrete in
+very cold weather, because of the danger of freezing
+and cracking. Sometimes the materials are heated,
+and after the concrete is in place, straw or sand or
+sawdust is spread over it. These will keep it warm for
+several hours, and so give the concrete a chance to
+"set." Sometimes a canvas house is built over the
+work. When a concrete dam was to be built in the
+Province of Quebec and the mercury was 20&deg; below
+zero, the contractors built a canvas house over one
+portion of the dam and set up iron stoves in it.
+When this part was completed, they took down the
+house and built it up again over another portion of
+the dam. Sometimes salt is used. Salt water is
+heavier than fresh water and will not freeze so
+easily. Therefore salt put into the water used in
+making the concrete will enable it to endure more
+cold without freezing; but not more than one pound
+of salt to twelve gallons of water should be used.</p>
+<p><span class='pagenum'><a name="Page_27" id="Page_27">[Pg 27]</a></span></p>
+<p class="figcenter" style="width: 600px;">
+<img src="images/image027.jpg" width="600" height="310" alt="BUILDING A CONCRETE ROAD"
+ title="BUILDING A CONCRETE ROAD" />
+<span class="caption">BUILDING A CONCRETE ROAD<br /><br />
+
+<i><small>Courtesy Alpha Portland Cement Co.</small></i><br /><br />
+
+The concrete mixer travels along the prepared roadbed, and after it
+follow the workmen with levelers and stamps.</span>
+</p>
+
+<p><span class='pagenum'><a name="Page_28" id="Page_28">[Pg 28]</a></span></p>
+<p>Concrete objects to being frozen before it is "set,"
+but it is exceedingly accommodating about working
+under water. It must, of course, be carried in some
+way through the water to its proper place without
+being washed away, but this is easily done. Sometimes
+it is let down in great buckets closed at the
+top, but with a hinged bottom that will open when
+the bucket strikes the rock or soil where the material
+is to be left. Sometimes it is poured down through
+a tube. Sometimes it is dropped in sacks made of
+cloth. This cloth must be coarse, so that enough of
+the concrete will ooze through it to unite the bag
+and its contents with what is below it and make a
+solid mass. Sometimes even paper bags have been
+successfully used. The concrete, made rather dry,
+is poured into the bags and they are slid down a
+chute. The paper soon becomes soft and breaks,
+and lets the concrete out. Sometimes concrete
+blocks are moulded on land and lowered by a derrick,
+while a diver stands ready to see that they go
+into their proper places.</p>
+
+<p>Concrete is used for houses, churches, factories,
+walls, sidewalks, steps, foundations, sewers, chimneys,
+piers, cellar bottoms, cisterns, tunnels, and
+even bridges. In the country, it is used for silos,<span class='pagenum'><a name="Page_29" id="Page_29">[Pg 29]</a></span>
+barn floors, ice houses, bins for vegetables, box
+stalls for horses, doghouses, henhouses, fence posts,
+and drinking-troughs. It is of very great value in
+filling cavities in decaying trees. All the decayed
+wood must be cut out, and some long nails driven
+from within the cavity part-way toward the outside,
+so as to help hold the concrete. Then it is poured
+in and allowed to harden. If the cavity is so large
+that there is danger of the trunk's breaking, an
+iron pipe may be set in to strengthen it. If this is
+encased in concrete, it will not rust. A horizontal
+limb with a large cavity may be strengthened by
+bending a piece of piping and running one part of
+it into the limb and the other into the trunk, then
+filling the whole cavity with concrete. If the bark
+is trimmed in such a way as to slant in toward the
+cavity, it will sometimes grow entirely over it.</p>
+
+<p>Concrete is also used for stucco work, that is, for
+plastering the outside of buildings. If the building
+to be stuccoed is of brick or stone, the only preparation
+needed is to clean it and wet it; then put on
+the plaster between one and two inches thick. A
+wooden house must first be covered with two thicknesses
+of roofing-paper, then by wire lathing. The
+concrete will squeeze through the lathing and set.
+Stucco work is nothing new, and if it is well done,
+it is lasting.</p>
+
+<p>Concrete has been used for many purposes besides
+building, and the number of purposes increases
+rapidly. For blackboards, refrigerator linings, and
+railroad ties it has been found available, and for<span class='pagenum'><a name="Page_30" id="Page_30">[Pg 30]</a></span>
+poles or posts of all sizes it has already proved itself
+a success. It has even been suggested as an excellent
+material for boats, if reinforced; and minute directions
+are given by one writer for making a concrete
+rowboat. To do this, the wooden boat to be copied
+is hung up just above the ground, and clay built
+around it, leaving a space between boat and clay
+as thick as the concrete boat is to be. The wooden
+boat is covered with paper and greased, then the
+concrete is poured into the space between the boat
+and the clay mould; and when it hardens and the
+wooden boat is removed, there is a boat of stone&mdash;or
+so the directions declare; but I think most people
+would prefer one of wood. However it may be with
+rowboats, concrete is taking an important place in
+the construction of battleships, a backing for armor
+being made of it instead of teakwood. The Arizona
+is built in this way.</p>
+
+<p>Concrete that is carelessly made is very poor
+stuff, and dangerous to use, for it is not at all reliable
+and may give out at any time; but concrete that
+is made of the best materials and properly put together
+is an exceedingly valuable article.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_31" id="Page_31">[Pg 31]</a></span></p>
+<h2><a name="IV" id="IV"></a>IV</h2>
+
+<h3>BRICKS, THEIR FAULTS AND THEIR VIRTUES</h3>
+
+
+<p>The simplest way to make a brick is to fill a
+mould with soft clay, then take it out and let it
+stiffen, and then put it in the sun to dry. This is
+the way in which the "adobe" bricks of Central
+America are made. They answer very well in countries
+where there is little rain; but one or two heavy
+downpours would be likely to melt a house built of
+such material.</p>
+
+<p>Clay is a kind of earth containing mostly alumina
+and silica or sand, that can be mixed with water,
+moulded into any shape, retain that shape after it
+is dry, and become hard by being burned. If you
+want to make a china cup, you must have a fine sort
+of clay called "kaolin," which is pure white when
+it is fired and is not very common; but if you want
+to make bricks, it will not be at all difficult to find
+a suitable clay bank. And yet the clay, even for
+bricks, must be of the right kind. If it contains too
+much silica (sand), the brick will not mould well;
+if too much alumina it will be weak; if too much
+iron, it will lose its shape in burning; if too much
+lime, it will be flesh-colored when it is burned.</p>
+
+<p>If you want to find out whether a building-brick
+is of good quality, there are some tests that a boy
+or girl can apply as well as any one. First, look the
+brick over and note whether it is straight and true,<span class='pagenum'><a name="Page_32" id="Page_32">[Pg 32]</a></span>
+and whether the edges and corners are sharp. Strike
+it, and see whether it gives a clear, ringing sound.
+Then weigh it and soak it in water for twenty-four
+hours. Weigh it again, and if it is more than one
+fifth heavier than it was before soaking, it is not
+of the first quality.</p>
+
+<p>After the clay has been dug, it must be "tempered,"
+that is, mixed with water and about one
+third or one fourth as much sand as clay, and left
+overnight in a "soak pit," a square pit about five
+feet deep. In the morning the workmen shovel the
+mass over and feed it into the machines for forming
+the bricks. The mixing is better done, however, in
+a "ring pit." This is a circular pit twenty-five or
+thirty feet in diameter, three feet deep, and lined
+with boards or brick. A big iron wheel works from
+the center to the edge and back again for several
+hours, through and through the clay. A method
+even better than this is to put the clay and sand
+and water into a great trough, in which there is a
+long shaft bristling with knives. The shaft revolves,
+mixes the clay, and pushes it along to the end of
+the trough. This is called "pugging," and the
+whole thing&mdash;trough, shaft, and knives&mdash;is a "pug
+mill."</p>
+
+<p>In the old days bricks were always made by hand.
+The moulder stood in front of a wet table whereon
+lay a heap of soft clay. He either wet or sanded
+his mould to keep it from sticking. Meanwhile, his
+assistant had cut a piece of clay and rolled it and
+patted it into the shape of the mould. In making
+bricks, there can be no patching; the mould must
+be filled at one stroke, or else there will be folds in
+the brick. To make a good brick, the moulder lifts
+the clay up above his head and throws it into the
+mould with all his force. Then he presses it into
+the corners with his thumbs, scrapes off with a
+strip of wood any extra clay, or cuts it off with a
+wire, smooths the surface of the brick, puts mould
+and brick upon a board, jerks the mould up and
+proceeds to make another brick.</p>
+<p><span class='pagenum'><a name="Page_33" id="Page_33">[Pg 33]</a></span></p>
+<p class="figcenter" style="width: 367px;">
+<img src="images/image033.jpg" width="367" height="580" alt="IN A NEW JERSEY BRICK MILL"
+ title="IN A NEW JERSEY BRICK MILL" />
+<span class="caption">IN A NEW JERSEY BRICK MILL<br /><br />
+
+<i><small>Copyright by Underwood and Underwood.</small></i><br /><br />
+
+This man is moulding a fire-brick to its final shape.</span>
+</p>
+
+<p><span class='pagenum'><a name="Page_34" id="Page_34">[Pg 34]</a></span></p>
+<p>No matter how expert a moulder may be, brick-making
+by hand is slow work, and in most places
+machines are used. In what is called the "soft-mud"
+process, the clay is pushed on by the pug mill to the
+end of the trough. There stands a mould for six
+bricks. A plunger forces the clay into it, the mould
+is emptied, and in a single hour five thousand bricks
+can be made. By what is called the "stiff-mud"
+process, the stiff clay is put into a machine with an
+opening the size of the end or side of a brick. The
+machine forces the clay through this opening, cuts
+it off at the proper moment; and so makes bricks
+by the thousand without either mould or moulder.
+A third way of making brick is by what is called
+the "dry process." The clay is pulverized and filled
+into moulds the length and breadth of a brick, but
+much deeper, and with neither top nor bottom. One
+plunger from above and another from below strike
+the clay in the mould with much force, and make
+the fine, smooth brick known as "pressed brick."
+All this is done by machinery, and some machines<span class='pagenum'><a name="Page_35" id="Page_35">[Pg 35]</a></span>
+make six bricks at a time. These "dry" bricks are
+fragile before they are burned, and must be handled
+with great care.</p>
+
+<p>Bricks cannot be put into the kiln while they are
+still wet, for when a brick is drying, it is a delicate
+article. It objects to being too hot or too cold, and
+it will not stand showers or drafts. In some way
+about a pound of water must be dried out of each
+brick; but if you try to hurry the drying, the brick
+turns sulky, refuses to have anything more to do
+with you, and proceeds to crack. To dry, bricks are
+sometimes spread on floors; or piled up in racks on
+short pieces of board called "pallets"; and sometimes
+they are put upon little cars and run slowly
+through heated tunnels. The last is the best way
+for people who are in a hurry, for it takes only from
+twenty-four to thirty-six hours to make the bricks
+ready to go to the kiln to be burned.</p>
+
+<p>In one sort of kiln, the bricks themselves make
+the kiln. They are piled up in arches, but left a
+little way apart so the hot air can move freely
+among them. The sides of the structure are covered
+with burnt brick and mud, but the top is left open
+to allow the steam from the hot bricks to escape.
+The fires are in flues that are left at the bottom.
+They must burn slowly at first, but after a while,
+some forty to sixty hours, the heat becomes intense.
+Thus far the bricks have been grayish or cream-colored,
+but now, if there is iron in them, they turn
+red; if there is lime, they turn yellow; if a large
+amount of lime, they become flesh-colored. Besides<span class='pagenum'><a name="Page_36" id="Page_36">[Pg 36]</a></span>
+this sort of kiln, which is torn down when the
+bricks are sufficiently burned, there is also the permanent
+kiln, which has fixed side walls and either
+an open or closed top. Then, too, there is a "continuous"
+kiln. This has a number of chambers, and
+the heat from each one passes into the next; so that
+bricks in one chamber may be just warming up
+while in another they are ready to be taken out.</p>
+
+<p>When the bricks come out of the kiln, some of
+them are good and some are not. Those that were
+on the outside are not burned enough; those next it
+are not well baked, but can be used for the middle
+of thick walls. The next ones are of good quality; but
+those directly over the fires are so hard and brittle
+that they are of little use except for pavements.</p>
+
+<p>Paving-bricks, however, are not to be despised.
+They are not as smooth and well finished as pressed
+brick, but they are exceedingly useful. They need
+as much care in making as any others, and they
+must be burned in a much hotter fire to make them
+dense and hard. The tests for paving-bricks are
+quite different from those for ordinary building-brick.
+If first-class paving-bricks weighing fifty
+pounds are soaked in water for twenty hours, they
+take up so little water that they will not weigh
+more than fifty-one or fifty-one and a half pounds
+when taken out. To find out how hard they are,
+the bricks are weighed and shaken about with
+foundry shot for a number of hours. Then they are
+weighed again to see how much of their material
+has been rubbed off. A third test is to put one<span class='pagenum'><a name="Page_37" id="Page_37">[Pg 37]</a></span>
+brick on edge into a crushing machine to see how
+much pressure it will stand. Paving-brick is cheaper
+than granite blocks, and if it has a good foundation
+of concrete covered with sand, it will last about
+three fourths as long. Brick is less noisy than stone
+and is easier to clean.</p>
+
+<p>Not so very long ago, when particularly handsome
+bricks were needed for the outside of walls and other
+places where they would be conspicuous, they were
+"re-pressed"; that is, they were made by hand or
+in a "soft-mud" machine, and then, after drying
+for a while, were put into a re-pressing machine to
+give them a smooth finish. These machines are still
+used, but they are hardly necessary, for the "dry-clay"
+brick machine will turn out a smooth brick
+in one operation.</p>
+
+<p>Another substance which is made of almost the
+same materials as brick is terra cotta. To make
+this, fire brick, bits of pottery, partly burned clay,
+and fine white sand are ground to a powder and
+mixed very thoroughly. This mixture is moulded,
+dried, and burned. Until recently, all terra cotta
+was of the color that is called by that name, but
+now it is made in gray, white, and bronze as well.</p>
+
+<p>Bricks are laid in mortar, and this makes a wall
+one solid mass and stronger than it could be without
+any cement. But mortar does more than this. It
+is more elastic than brick, and therefore, when a
+wall settles, the mortar yields a little, and this often
+prevents the bricks from cracking. Bricks are always
+thirsty, and if one is laid in mortar, it will<span class='pagenum'><a name="Page_38" id="Page_38">[Pg 38]</a></span>
+suck the moisture out of it almost as a sponge will
+suck up water. The mortar thus has no chance to
+set, and so is not strong as it should be. That is why
+the bricklayer wets his bricks, especially in summer,
+before he puts them in place. Lime or cement
+mortar will not set in freezing weather, and a brick
+building put up in the winter is in danger of tumbling
+down when the warm days of spring arrive.</p>
+
+<p>This thirstiness of bricks is their greatest fault.
+Three or four days of driving rain will sometimes
+wet through a brick wall two feet thick, crumbling
+the plaster and spoiling the wallpaper. That is
+why it is a poor plan to plaster directly on the
+brick wall of a house. "Furring" strips, as they are
+called, or narrow strips of wood, should be fastened
+on first and the laths nailed to these, or the wall
+can be painted or oiled on the outside. The best
+way, however, though more expensive, is to build
+the wall double. Then there is air between the two
+thicknesses of brick. Air is a poor conductor of
+heat; so in summer it keeps the heat out, and in
+winter it keeps it in.</p>
+
+<p>But brick will suck up water from the ground as well
+as from a storm; and therefore, when a brick house
+is to be built in a wet place, there ought to be a three-eighths-inch
+layer of something waterproof, like asphalt
+and coal tar, put on top of one of the layers of
+brickwork to prevent the moisture from creeping up.</p>
+
+<p>Bricks have their faults, but they will not burn,
+and when properly used, they make a most comfortable
+and enduring house.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_39" id="Page_39">[Pg 39]</a></span></p>
+<h2><a name="V" id="V"></a>V</h2>
+
+<h3>AT THE GOLD DIGGINGS</h3>
+
+
+<p>When gold was first discovered in California, in
+1848, people from all over the world made a frantic
+rush to get there, every one of them hoping that he
+would be lucky enough to make his fortune, and
+fearing lest the precious metal should be gone before
+he could even begin to dig. The gold that
+these men gathered came from what were called
+"placers"; that is, masses of gravel and sand along
+the beds of mountain streams. Each miner had a
+pan of tin or iron, which he filled half-full of the
+gravel, or "pay dirt," as the miners called it. Then,
+holding it under water, he shook off the stones and
+mud over the side of the pan, leaving grains of gold
+mixed with black sand at the bottom. This black
+sand was iron, and after a while the miners removed
+it with a magnet, dried what remained, and blew
+away the dust, leaving only the grains of gold.</p>
+
+<p>Another contrivance which soon came into use
+was the "cradle." This was a long box, sometimes
+only a hollowed-out log. At the top was a sieve
+which sifted out the stones. Nailed to the bottom
+of the cradle were small cleats of wood, or "riffles,"
+which kept the water from running so fast as to
+sweep the gold out of the cradle with it. The cradle
+was placed on rockers and was also tilted slightly.
+The miner shoveled the gravel into the top of the<span class='pagenum'><a name="Page_40" id="Page_40">[Pg 40]</a></span>
+cradle and his partner rocked it. The sieve kept
+back the stones, the water broke up the lumps of
+earth and gravel and washed them down the cradle,
+and the grains of gold were stopped by the riffles,
+and sank to the bottom. Sometimes the "pay dirt"
+continued under a stream. To get at it, the miners
+often built a little canal and turned the water into
+a new channel; then they could work on the former
+bed of the river.</p>
+
+<p>Before many years had passed, the gold that was
+near the surface had been gathered. The miners
+then followed the streams up into the mountains,
+and found that much of the gold had come from
+beds where in ancient times rivers had flowed.
+There was gold still remaining in these beds, but it
+was poorly distributed, the miners thought. Sometimes
+there would be quite an amount in one place,
+and then the miner would dig for days without
+finding any more. Even worse than this was the
+fact that these gravel beds were not on the top of
+the ground, but were covered up with soil and trees.
+Evidently the slow work with pans and cradles
+would not pay here; but it occurred to some one
+that if a powerful stream of water could be directed
+against the great banks of earth, as water is directed
+against a burning building, they would crumble, the
+dirt could be washed down sluices, and the gold be
+saved. This was done. Great reservoirs were built
+high up in the mountains, and water was brought
+by means of ditches or pipes to a convenient place.
+Then it was allowed to rush furiously through a
+hose and nozzle, and the great stream coming with
+tremendous force was played upon the banks of
+gravel. The banks crumbled, the gravel was washed
+into a string of sluices, or long boxes with riffles to
+catch the gold. Soon the miners found that if
+quicksilver was put into these sluices, it would unite
+with the gold and make a sort of paste called
+"amalgam." Then if this amalgam was heated, the
+quicksilver would be driven off in the form of gas,
+and the gold would remain in a beautiful yellow
+mass.</p>
+<p><span class='pagenum'><a name="Page_41" id="Page_41">[Pg 41]</a></span></p>
+<p class="figcenter" style="width: 800px;">
+<img src="images/image042.jpg" width="800" height="415" alt="HYDRAULIC GOLD MINING"
+ title="HYDRAULIC GOLD MINING" />
+<span class="caption">HYDRAULIC GOLD MINING<br /><br />
+
+A placer mine at Gold Point, California, where tremendous streams of
+water under high pressure are busy washing away the side of a
+gold-bearing hill.</span>
+</p>
+
+<p><span class='pagenum'><a name="Page_42" id="Page_42">[Pg 42]</a></span></p>
+<p>The ancient rivers had also carried gold to the valleys,
+and to collect this a dredge, which the miners
+called a "gold ship," came into use. The "ship"
+part of this machine is an immense flat scow.
+Stretching out from one end is something which
+looks like a moving ladder. This is the support of
+an endless chain of buckets, each of which can bite
+into the gravel and take a mouthful of five or six
+hundred pounds. They drop this gravel into a big
+drum which is continually revolving. Water flows
+through the drum, and washes out the sand and
+bits of gold over large tables, where by means of
+riffles and quicksilver the gold is captured. This
+scow was usually on dry land at first; but its digging
+soon made a lake, and then it floated. It must
+be more fascinating to hold a pan in your own hands
+and pick out little grains of gold or perhaps even
+a big piece of it with your own fingers, but if the
+gravel is good the dredge makes more money.</p>
+
+<p>In Alaska the great difficulty in mining is that,<span class='pagenum'><a name="Page_43" id="Page_43">[Pg 43]</a></span>
+except at the surface, the ground is frozen all the
+year round. At first, the miners used to thaw the
+place where they wished to dig by building wood
+fires; but this was a slow method, and now the
+thawing is done by steam. They carry the steam
+in a pipe to the place where the digging is to be
+done, and send it through a hose. At the end of the
+hose is a pointed steel tube. They hammer this tube
+into the ground and let some steam pass through
+the nozzle. This softens the ground so that picks
+and shovels may be used. There is generally cold
+enough in Alaska, but once at least the miners had
+to manufacture it. The gold-bearing gravel was
+deep, the ground was flat, and it was often overflowed.
+They set up a freezing plant, and shut in
+their land with a bulkhead of ice several feet thick.
+Then they pumped out what water was already in
+and did their work with no more trouble.</p>
+
+<p>When gold began to grow less in the California
+gravel, the miners looked for it in the rocks on the
+mountain-side. The placer miners laughed at them
+and called their shafts "coyote holes"; but in time
+the placers failed, while nearly all of our gold to-day
+comes from veins of white quartz in the rocks. A
+vein of gold is the most capricious thing in the
+world. It may be so tiny that it can hardly be seen,
+then widen and grow rich in gold, then suddenly
+come to an end. This is why a new mine is so uncertain
+an enterprise. The gold may hold out and
+bring fortunes to the investors, or it may fail, and
+then all they will have to show for their money is the<span class='pagenum'><a name="Page_44" id="Page_44">[Pg 44]</a></span>
+memory that they put it into a hole in the ground.
+The managers of a few of the well-established mines,
+however, have explored so far as to make sure that
+there is gold enough for many years of digging.</p>
+
+<p>The mining engineer must be a very wide-awake
+man. It is not enough for him simply to remember
+what was taught him in the schools of mining; he
+must be bright enough to invent new ways of meeting
+difficulties. No two mines are alike, and he
+must be ready for all sorts of emergencies. A gold
+mine now consists of a shaft or pit dug several hundred
+feet down into the rock, with levels or galleries
+running off from it and with big openings like
+rooms made where the rock was dug out. The roofs
+of the rooms are supported by great timbers. To
+break away the rock, the miner makes a hole with
+a rock drill worked by electricity or compressed air,
+puts powder or dynamite into the hole and explodes
+it. The broken rock is then raised to the surface
+and crushed in a "stamping mill." Here the
+ore is fed into a great steel box called a "mortar."
+Five immense hammers, often weighing a thousand
+pounds apiece, drop down upon the ore, one after
+another, until it is fine enough to go through a wire
+screen in the front of the box. When two hundred
+or more of these hammers are pounding away with
+all their might, a stamping mill is a pretty noisy
+place. The ore, crushed to a fine mud, now runs
+over sloping tables covered with copper. Sticking
+to the top of the copper is a film of quicksilver.
+This holds fast whatever gold there may be and<span class='pagenum'><a name="Page_45" id="Page_45">[Pg 45]</a></span>
+makes an amalgam, which is scraped off from time
+to time, and the quicksilver is driven from the gold
+by heat.</p>
+
+<p>Gold that is not united with other metals is called
+"free milling gold." Much of it, however, is found
+in combination with one metal or another, and is
+known as "rebellious" or "refractory" gold. Such
+gold may sometimes be set free by heat, and sometimes
+by chemicals. One way is by the use of chlorine
+gas, and the story of it sounds almost like "The
+house that Jack built." It might run somewhat like
+this: This is the salt that furnishes the chlorine. This
+is the chlorine gas that unites with the gold. This is
+the chloride that is formed when the chlorine gas
+unites with the gold. This is the water that washes
+from the tank the chloride that is formed when the
+chlorine gas unites with the gold. This is the sulphate
+of iron that unites with the chlorine gas of the
+chloride that the water washes from the tank that
+is formed when the chlorine gas unites with the gold&mdash;and
+leaves the gold free.</p>
+
+<p>Another method is by the use of cyanide. More
+than a century ago a chemist discovered that if gold
+was put into water containing a little cyanide, the
+gold would dissolve, while quartz and any metals
+that might be united with the gold would settle in
+the tank. The water in which the gold is dissolved
+is now run into boxes full of shavings of zinc and is
+"precipitated" upon them; that is, the tiny particles
+of gold in the water fall upon the zinc and cling to it.
+Zinc melts more easily than gold, so if this gilded<span class='pagenum'><a name="Page_46" id="Page_46">[Pg 46]</a></span>
+zinc is put into a furnace, the zinc melts and the gold
+is set free.</p>
+
+<p>Very often gold is found combined with lead or
+copper. It must then be melted or smelted in great
+furnaces. The metal is heavier than the rock and
+settles to the bottom of the furnace. It is then
+drawn off and the gold is separated from the other
+metals, usually by electricity.</p>
+
+<p>Sometimes large pieces of gold called "nuggets"
+are found by miners. The largest one known was
+found in Australia. It weighed 190 pounds and was
+worth $42,000. Sometimes spongy lumps of gold
+are found; but as a general thing gold comes from
+the little specks scattered through veins in rock, and
+much work has to be done before it can be made
+into coins or jewelry. It is too soft for such uses
+unless some alloy, usually copper or silver, is mixed
+with it to make it harder. Sometimes it is desirable
+to know how much alloy has been added. The
+jeweler then makes a line with the article on a peculiar
+kind of black stone called a "touchstone," and
+by the color of the golden mark he can tell fairly
+well how nearly pure the article is. To be more
+accurate, he pours nitric acid upon the mark. This
+eats away the alloy and leaves only the gold.</p>
+
+<p>Gold is a wonderful metal. It is of beautiful color;
+it can be hammered so thin that the light will shine
+through it; few acids affect it, and the oxygen which
+eats away iron does not harm it. Pure gold is spoken
+of as being "twenty-four carats fine," from <i>carat</i>,
+an old weight equal to one twenty-fourth of an<span class='pagenum'><a name="Page_47" id="Page_47">[Pg 47]</a></span>
+ounce troy. Watchcases are from eight to eighteen
+carats fine; chains are seldom more than fourteen;
+and the gold coins of the United States are about
+eleven parts of gold and one of copper. Coins wear
+in passing from one person to another, and that is
+why the edges are milled, so that it may be more
+easily seen when they have become too light to be
+used as coins. When such pieces come into the hands
+of the Government, they must be recoined.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_48" id="Page_48">[Pg 48]</a></span></p>
+<h2><a name="VI" id="VI"></a>VI</h2>
+
+<h3>THE STORY OF A SILVER MINE</h3>
+
+
+<p>A man who goes out in search of a mine is called
+a "prospector." The best prospector is a man who
+has learned to keep his eyes open and to recognize
+the signs of gold and silver and other metals. A
+faithful friend goes with him, a donkey or mule
+which carries his bacon and beans, blankets, saucepan,
+and a few tools, such as a pan, pick, shovel,
+hammer, and axe. Sometimes the prospector also
+takes with him a magnifying glass and a little acid
+to test specimens, but usually he trusts to his eyes
+alone.</p>
+
+<p>When these few things have been brought together,
+the prospector and the donkey set out. They
+wander over the hills and down into the canyons. If
+a rock is stained red, the prospector examines it to
+see whether it contains iron; if it is green, he looks
+for copper. In the canyons and along the creeks he
+often tests the gravel for traces of some valuable
+metal. If he finds any of these traces along the
+stream, he follows them on the bank until they stop;
+then he carefully examines the bank of the stream
+or the nearest hillside. If he continues to find bits
+of metal, they will lead him to a vein of ore, from
+which they have been broken by the wind, rain, and
+frost.</p>
+
+<p>Generally a prospector is looking for some one<span class='pagenum'><a name="Page_49" id="Page_49">[Pg 49]</a></span>
+special metal, and in his search he often overlooks
+some other metal; for instance, thousands of the
+gold-seekers who rushed to California in 1849 hurried
+through Nevada on their way. If they had only
+known what was under their feet, they would have
+taken their picks and shovels and begun to dig, instead
+of trying to get out of the region as soon as
+might be. Ten years later, the California placers
+were becoming exhausted, and miners began to go
+elsewhere in their search for gold.</p>
+
+<p>Among those who were working in what is now
+the State of Nevada were two Irishmen who had
+been unlucky in California and had fared no better
+in Nevada. They wanted to go somewhere else, but
+they had not money enough for the journey; so
+they kept on with their work at the foot of Mount
+Davidson, washing the gravel and saving the little
+gold that they found. They were annoyed by some
+heavy black stuff that united with the quicksilver
+in their cradles, interfered with the saving of the
+gold, and put them in a very bad temper. At length
+a man named Henry Comstock came along, who
+told them that this black stuff was silver ore. They
+examined the mountain-side, and discovered the
+outcrop or edge of a great vein containing gold and
+also silver. It is no wonder that people rushed from
+the east and west to the wonderful new mines, for
+it was plain that these new "diggings" were not
+mere placers, but rich veins that many years of
+working might not exhaust. Every newcomer hoped
+to discover a vein; and within a year or two the district<span class='pagenum'><a name="Page_50" id="Page_50">[Pg 50]</a></span>
+around the Comstock lode was full of deep
+shafts, many of them abandoned and half-hidden
+by low brush, but some of them yielding quantities
+of gold and silver. Before this, there had been only
+about a thousand people in what is now Nevada,
+but in two years after the discovery of silver, there
+were 16,000, and a new Territory was formed.</p>
+
+<p>The miners knew how to get gold out of ore, but
+silver was another matter, and some of it was difficult
+to extract. They had so much trouble that they
+were ready to believe in any treatment of the ore,
+no matter how absurd, that promised to help them
+out of their difficulties. Some of them were actually
+persuaded that the juice of the wild sagebrush would
+bring the silver out. It is no wonder that they were
+troubled, for in the Comstock lode were not only
+gold and silver, but ten or twelve other metals or
+combinations of silver with something else. At
+length processes were invented for treating the different
+kinds of ore. Some kinds were crushed in a
+stamping mill, then ground to a powder and mixed
+with quicksilver or mercury. This mercury united
+with both the gold and the silver, making an amalgam.
+The amalgam, together with the finely ground
+ore, was put into a "settler," and here the heavy
+amalgam sank to the bottom and was then strained.
+The extra mercury was collected, and the amalgam
+was put into a retort or kettle and heated. The
+mercury became a gas and was driven off from the
+gold and silver, then caught in a vessel cool enough
+to condense it, just as a cold plate held in steam
+will collect drops of water. Sometimes the ore was
+mixed with copper and lead. In that case common
+salt and copper sulphate were used. Some ore had
+to be roasted in a furnace in order to drive off the
+sulphur.</p>
+<p><span class='pagenum'><a name="Page_51" id="Page_51">[Pg 51]</a></span></p>
+<p class="figcenter" style="width: 600px;">
+<img src="images/image052.jpg" width="600" height="302" alt="THE STORY OF A SPOON"
+ title="THE STORY OF A SPOON" />
+<span class="caption">THE STORY OF A SPOON<br /><br />
+
+<i><small>Courtesy The Gorham Co.</small></i><br /><br />
+
+(1) Silver strip blanked. (2) Pinched. (3) Graded. (4) Outlining of Handle.
+(5) Stamped Handle. (6) Spoon completely trimmed. (7, 8) Finished spoons.</span>
+</p>
+
+<p><span class='pagenum'><a name="Page_52" id="Page_52">[Pg 52]</a></span></p>
+<p>There were great and unusual dangers to be met
+in getting the ore. The vein of quartz which bore it
+was fifty or sixty feet wide. Some was hard, and
+some so soft and crumbling that pillars would not
+hold up the roof. The passageways were then lined
+with heavy logs standing on either side, other logs
+laid across their tops, and all bolted firmly together.
+Nevertheless, they twisted and fell, and slowly but
+certainly the whole mass of earth and rock, two hundred
+or more feet in thickness, was coming down
+upon the heads of the miners. The work on the
+Comstock mines had come to an end unless a man
+could be found able to invent some system of support
+not laid down in the books. The man was
+found. He took short, square timbers five or six
+feet long, put them together as if they were the sides
+and ends of square boxes, and piled them one above
+another, making hollow pillars. He fastened these
+firmly together and filled the space inside with waste
+rock, thus making strong, solid pillars that would
+support almost any weight that could be put upon
+them.</p>
+
+<p>There were two other dangers, water and heat.
+The vein was porous and water was constantly
+trickling out of it. Then, too, there were "water
+pockets," or natural reservoirs in the rock, and any<span class='pagenum'><a name="Page_53" id="Page_53">[Pg 53]</a></span>
+moment the stroke of a pick might let out a torrent
+and force the miners to run for their lives. Sometimes
+minerals were dissolved in this water, and the
+men with closed eyes and swollen faces had to be
+hurried to the surface for treatment. Powerful
+pumps had to be used and the water sent away
+through long lines of pipes. This water was warm,
+and in very deep workings in the Comstock vein it
+was boiling hot. Even with quantities of ice sent
+down to cool them, the men could work in some
+places only a short time.</p>
+
+<p>In San Francisco there was a mining engineer
+named Adolph Sutro who planned to remedy these
+troubles by driving a big four-mile tunnel through
+the heart of the mountain, letting out the hot water
+and the foul air. The owners of some of the mines
+joined him in raising the money, and the tunnel was
+dug. Through this the water ran out. The mines
+were freed of foul air and fresh air was driven in.</p>
+
+<p>The Comstock lode has given up an amazing
+amount of precious metal. Between 1860 and 1890
+it produced $340,000,000. After 1890, however, its
+product grew less. The vein was not so rich, the
+price of silver fell, while the cost of mining it at
+great depths increased. Not nearly so much was
+mined, and at length water rose in the mines up to
+the level of the Sutro Tunnel. In 1900 new machinery
+was put in and new methods were adopted, such
+as treating the tailings with cyanide and so saving
+much of the precious metal from them. From the
+beginning the Comstock mines have been so ready<span class='pagenum'><a name="Page_54" id="Page_54">[Pg 54]</a></span>
+to follow improved methods that they have been
+called the mining school of the world.</p>
+
+<p>Great quantities of silver are used for making
+jewelry and for tableware. The one objection to its
+use is that silver likes to unite with sulphur, and
+thus the silver easily becomes black. There is sulphur
+in the yolk of an egg and that is why the spoon
+with which it has been eaten turns black. Even if
+silverware is not used, it tarnishes, especially in
+towns, because there is so much sulphureted hydrogen
+in the air. In perfectly pure air, it would not
+tarnish. Silver is harder than gold, but not hard
+enough to be used without some alloy, usually copper.
+Tableware is "solid" even if it contains alloy
+enough to stiffen it. It is "plated" if it is made of
+some cheaper metal and covered with silver. The
+old way of doing this was to fasten with bits of
+solder a thin sheet of silver to the cup or vase or
+whatever was in hand and heat it. This did fairly
+well for large, smooth articles; but it was almost
+impossible to finish the edges of spoons so as not to
+show the two metals. If you look at a plated spoon
+to-day, however, you will find that there is no break
+at the edge, and so far as you can tell by the eye, it
+is solid silver. If you look on the back of the spoon,
+you will perhaps see "Rogers Bros. 1846." These
+men were the first silvermakers in this country to
+plate tableware by electricity. To make a spoon,
+they formed one out of iron or copper and made
+sure that it was perfectly clean. Then across a bath
+of silver cyanide, potassium cyanide, and water they<span class='pagenum'><a name="Page_55" id="Page_55">[Pg 55]</a></span>
+laid two metal rods, and from these they hung a
+spoon at one end and a plate of silver at the other.
+These rods were connected with the two poles of a
+battery. The electrical current passed through them,
+released the silver from the silver cyanide, and this
+was deposited upon the spoon. The cyanide that
+had lost its silver took enough more from the silver
+plate to make up. The amount of silver on the spoon
+depends upon the length of time it remains in the
+bath. It is weighed before plating and again afterwards,
+to make sure that the proper amount of silver
+has been deposited upon it. On the back of
+many plated articles you will see the words "Triple
+plate" or "Quadruple plate." If the article has
+been made by a reliable firm, this means that the
+triple plate it manufactures contains three times as
+much silver as "single plate," and that quadruple
+plate contains four times as much. A piece of silver
+looks just as well if it has stayed in the bath only
+a few minutes, but of course it has taken on so little
+silver that this will soon wear off and show the
+cheaper metal.</p>
+
+<p>A large amount of silver is used for coins. When
+the United States needs dollars, half-dollars, quarters,
+and dimes, notice is given and offers are called
+for, stating the quantity for sale and its price. When
+it is delivered, it is first of all "assayed"; that is,
+tested to find out how nearly pure it is and how much
+it is worth. Next it is refined, or purified from other
+metals, mixed with a little copper to harden it, then
+melted again and poured into moulds to make bars.<span class='pagenum'><a name="Page_56" id="Page_56">[Pg 56]</a></span>
+If dollars are to be made, the bar is made thinner
+by passing it between heavy rollers, and blanks for
+dollars are cut out with a die. These blanks are
+weighed and every one that is too heavy or too light
+is put back to be melted over again. Thus far these
+dollars are only round, smooth pieces of metal. They
+must be milled to give them a rough edge, and they
+must be stamped. For stamping, the piece of metal
+is placed between two dies, one above and one below,
+and these close upon it with a force of one hundred
+and fifty tons. Every part of the process of manufacturing
+money is carried on with the utmost care.
+The places where coins are made are called "mints."
+The United States has four; the oldest is in Philadelphia,
+and there are branch mints in San Francisco,
+New Orleans, and Denver. Coins minted in Philadelphia
+have no distinguishing mark; but coins
+minted in San Francisco are marked with a tiny
+"S"; if minted in New Orleans, with an "O"; and if
+in Denver, with a "D."</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_57" id="Page_57">[Pg 57]</a></span></p>
+<h2><a name="VII" id="VII"></a>VII</h2>
+
+<h3>IRON, THE EVERYDAY METAL</h3>
+
+
+<p>Did you ever realize that your food and clothes,
+your books, and the house in which you live all
+depend upon iron? Vegetables, grains, and fruits
+are cultivated with iron tools; fish are caught with
+iron hooks, and many iron articles are used in the
+care and sale of meat. Clothes are woven on iron
+looms, sewed with iron needles, and fastened together
+with buttons containing iron. Books are
+printed and bound by iron machines, and sometimes
+written with iron pens or on iron typewriters.
+Houses are put together with nails; and indeed,
+there is hardly an article in use that could be made
+as well or as easily if iron was not plenty. If you
+were making a world and wanted to give the people
+the most useful metal possible, the gift would have
+to be iron; and the wisest thing you could do would
+be to put it everywhere, but in such forms that the
+people would have to use their brains to make it of
+service.</p>
+
+<p>This is just the way with the iron in our world.
+Wherever you see a bank of red sand or red clay or
+a little brook which leaves a red mark on the ground
+as it flows, there is iron. Iron is in most soils, in red
+bricks, in garnets, in ripening apples, and even in
+your own blood. It forms one twentieth part of the<span class='pagenum'><a name="Page_58" id="Page_58">[Pg 58]</a></span>
+crust of the earth. Iron dissolves in water if you
+give it time enough. If you leave a steel tool out of
+doors on a wet night, it will rust; that is, some of the
+iron will unite with the oxygen of the water. This is
+rather inconvenient, and yet in another way this
+dissolving is a great benefit. Through the millions
+of years that are past, the oxygen of the rain has
+dissolved the iron in the hills and has worked it
+down, so that now it is in great beds of ore or in rich
+"pockets" that are often of generous size. One of
+them, which is now being mined in Minnesota, is
+more than two miles long, half a mile wide, and of
+great thickness. The rains are still at work washing
+down iron from the hills. They carry the tiny particles
+along as easily as possible until they come upon
+limestone. Then, almost as if it was frightened, the
+brook drops its iron and runs away as fast as it can.
+Sometimes it flows into a pond or bog in which are
+certain minute plants or animals that act as limestone
+does, and the particles of iron fall to the bottom
+of the pond. In colonial days much of the iron
+worked in America was taken from these deposits.
+One kind of iron is of special interest because it
+comes directly from the sky, and falls in the shape of
+stones called "meteorites," some of which weigh
+many tons. In some of the old fables about wonderful
+heroes, the stories sometimes declare that the
+swords with which they accomplished their deeds of
+prowess fell straight from the heavens, which probably
+means that they were made of meteoric iron.
+Fortunately for the people and their homes, meteorites<span class='pagenum'><a name="Page_59" id="Page_59">[Pg 59]</a></span>
+are not common, but every large museum has
+specimens of them.</p>
+
+<p>It is not especially difficult to make iron if you
+have the ore, a charcoal fire in a little oven of stones,
+and a pair of bellows. Put on layers of charcoal alternating
+with layers of ore, blow the bellows, and by
+and by you will have a lump of iron. It is not really
+melted, but it can be pounded and worked. This is
+called the "Catalan method," because the people of
+Catalonia in Spain made iron in this way. It is still
+used by the natives of the interior of Africa. But if
+all the iron was made by this method, it would be
+far more costly than gold. The man who makes iron
+in these days must have an immense "blast furnace,"
+perhaps one hundred feet high, a real "pillar
+of fire." Into this furnace are dropped masses of
+ore, and with it coke to make it hotter and limestone
+to carry off the silica slag, or worthless part. To
+increase the heat, blasts of hot air are blown into
+the bottom of the furnace. This air is heated by
+passing it through great steel cylinders as high as
+the furnace. The fuel used is nothing more than the
+gases which come out at the top of the furnace.</p>
+
+<p>The slag is so much lighter than iron that when
+the ore is melted the slag floats on top just as oil
+floats on water, and can be drained out of the furnace
+through a higher opening than that through
+which the iron flows. The slag tap is open most of the
+time, but the iron tap is opened only once in about
+six hours. It is a magnificent sight when a furnace
+is "tapped" and the stream of iron drawn off.<span class='pagenum'><a name="Page_60" id="Page_60">[Pg 60]</a></span>
+Imagine a great shed, dark and gloomy, with many
+workmen hurrying about to make ready for what
+is to come. The floor is of sand and slopes down
+from the furnace. Through the center of this floor
+runs a long ditch straight from the furnace to the
+end of the shed. Opening from it on both sides are
+many smaller ditches; and connecting with these
+are little gravelike depressions two or three feet long
+and as close together as can be. These are called
+"pigs." When the time has come, the workmen
+gather about the furnace, and with a long bar they
+drill into the hard-baked clay of the tapping hole.
+Suddenly it breaks, and with a rush and a roar the
+crimson flood of molten iron gushes out. It flows
+down the trench into the ditches, then into the pigs,
+till their whole pattern is marked out in glowing
+iron. Now the blast begins to drive great beautiful
+sparks through the tapping hole. This means that
+the molten iron is exhausted. The blast is turned
+off, and the "mud-gun" is brought into position and
+shoots balls of clay into the tapping hole to close it
+for another melting, or "drive." The crimson pigs
+become rose-red, darken, and turn gray. The men
+play streams of water over them and the building
+is filled with vapor. As soon as the pigs are cool
+enough, they are carted away and piled up outside
+the building.</p>
+
+<p>In some iron works moulds of pressed steel carried
+on an endless chain are used instead of sand floors.
+The chain carries them past the mouth of a trough
+full of melted iron. They are filled, borne under
+water to be cooled, and then dropped upon cars. A
+first-class machine can make twenty pigs a minute.</p>
+<p><span class='pagenum'><a name="Page_61" id="Page_61">[Pg 61]</a></span></p>
+<p class="figcenter" style="width: 368px;">
+<img src="images/image062.jpg" width="368" height="580" alt="IN THE STEEL FOUNDRY"
+ title="IN THE STEEL FOUNDRY" />
+<span class="caption">IN THE STEEL FOUNDRY<br /><br />
+
+It is a dangerous business to visit a steel mill. Tremendous kettles
+travel overhead on huge cranes, hot metal flows from unexpected places,
+and there is a constant glow and steam and roar everywhere to confuse
+the unwary.</span>
+</p>
+
+<p><span class='pagenum'><a name="Page_62" id="Page_62">[Pg 62]</a></span></p>
+<p>Most of the iron made in blast furnaces is turned
+into steel. Steel has been made for centuries, but
+until a few years ago the process was slow and
+costly. A workman's steel tools were treasures, and
+a good jackknife was a valuable article. Railroads
+were using iron rails. They soon wore out, but at
+the suggestion to use steel, the presidents of the
+roads would have exclaimed, "Steel, indeed! We
+might as well use silver!" Trains needed to be
+longer and heavier, but iron rails and bridges could
+not stand the strain. Land in cities was becoming
+more valuable; higher buildings were needed, but
+stone was too expensive. Everywhere there was a
+call for a metal that should be strong and cheap.
+Iron was plentiful, but steel was dear. A cheaper
+method of making iron into steel was needed; and
+whenever there is pressing need of an invention, it
+is almost sure to come. Before long, what is known
+as the "Bessemer process" was invented. One great
+difficulty in the manufacture of steel was to leave
+just the right amount of carbon in the iron. Bessemer
+simply took it all out, and then put back exactly
+what was needed. Molten iron, tons and tons
+of it, is run into an immense pear-shaped vessel
+called a "converter." Fierce blasts of air are forced
+in from below. These unite with the carbon and
+destroy it. There is a roar, a clatter, and a clang.
+Terrible flames of glowing red shoot up. Suddenly
+they change from red to yellow, then to white; and<span class='pagenum'><a name="Page_63" id="Page_63">[Pg 63]</a></span>
+this is the signal that the carbon has been burned
+out. The enormously heavy converter is so perfectly
+poised that a child can move it. The workmen
+now tilt it and drop in whatever carbon is needed.
+The molten steel is poured into square moulds,
+forming masses called "blooms," and is carried
+away. More iron is put into the converter, and the
+work begins again.</p>
+
+<p>The Bessemer process makes enormous masses of
+steel and makes it very cheaply; but it has one
+fault&mdash;it is too quick. The converter roars away
+for a few minutes, till the carbon and other impurities
+are burned out; and the men have no control
+over the operation. In what is called the "open-hearth"
+process, pig iron, scrap iron, and ore are
+melted together with whatever other substances
+may be needed to make the particular kind of steel
+desired. This process takes much longer than the
+Bessemer, but it can be controlled. Open-hearth
+steel is more homogeneous,&mdash;that is, more nearly
+alike all the way through,&mdash;and is better for some
+purposes, while for others the Bessemer is preferred.</p>
+
+<p>Steel is hard and strong, but it has two faults.
+A steel bar will stand a very heavy blow and not
+break, but if it is struck gently many thousand
+times, it sometimes crystallizes and may snap. A
+steel rail may carry a train for years and then may
+crystallize and break and cause a wreck. Inventors
+are at work discovering alloys to prevent this crystallization.
+The second fault of steel is that it rusts
+and loses its strength. That is why an iron bridge or<span class='pagenum'><a name="Page_64" id="Page_64">[Pg 64]</a></span>
+fence must be kept painted to protect it from the
+moisture in the air.</p>
+
+<p>If all the iron that is in use should suddenly disappear,
+did you ever think what would happen?
+Houses, churches, skyscrapers, and bridges would
+fall to the ground. Railroad trains, automobiles, and
+carriages would become heaps of rubbish. Ships
+would fall apart and become only scattered planks
+floating on the surface of the water. Clocks and
+watches would become empty cases. There would
+be no machines for manufacturing or for agriculture,
+not even a spade to dig a garden. Everybody
+would be out of work. If you wish to see how it
+would seem, try for an hour to use nothing that is
+of iron or has been made by using iron.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_65" id="Page_65">[Pg 65]</a></span></p>
+<h2><a name="VIII" id="VIII"></a>VIII</h2>
+
+<h3>OUR GOOD FRIEND COPPER</h3>
+
+
+<p>Where did rocks come from?</p>
+
+<p>Some were deposited in water, like limestone and
+like the shale and sandstone that lie over the strata
+of coal. Others were made by fire, and were thrown
+up in a melted state from the interior of the earth.
+Such rocks are the Giant's Causeway in Ireland
+and the Palisades of the Hudson River. They are
+called "igneous" rocks, from the Latin word <i>ignis</i>
+meaning "fire."</p>
+
+<p>When the igneous rocks were thrown up to the
+surface of the earth, they brought various metals
+with them. How the metals happened to be there
+ready to be brought up, no one knows. Some people
+think they were dissolved in water and then deposited;
+others think that electricity had something
+to do with their formation. However that may be,
+metals were brought up with the igneous rocks, and
+one of these metals is copper.</p>
+
+<p>Now, to one who did not know how to work iron,
+copper was indeed a wonderful treasure, for it made
+very good knives and spoons. The people who
+lived in this country long before the Indians came
+understood how to use it, and after a while the
+Indians themselves found out its value. They did
+not trouble themselves to dig for it; they simply
+picked it up from the ground, good pure metal in<span class='pagenum'><a name="Page_66" id="Page_66">[Pg 66]</a></span>
+lumps; and with stones for hammers they beat it
+into knives.</p>
+
+<p>There was only one place in what is now the
+United States where they could do this, and that
+was in northern Michigan. A long point of land
+stretches out into Lake Superior as if it was trying
+to see what could be found there. Just beyond its
+reach is Isle Royal; and in these two places there
+was plenty of copper, enough for the Indians,
+enough for the people who have come after them,
+and enough for a great many more. One piece of
+copper which the Indians did not pick up, and
+the United States Government did, is the famous
+Ontonagon Boulder, so called because it was found
+near the Ontonagon River. It weighs more than
+three tons. The Indians would have been glad to
+make use of it, but it was too hard for their tools,
+and so they are said to have worshiped it as a god.
+It is now in the National Museum in Washington.</p>
+
+<p>The lumps of copper, such as those which delighted
+the hearts of the Indians, are known to-day
+as "barrel" copper, because they are of a good size
+to be dropped into barrels and carried away for
+smelting. The great boulders which the Indians
+could not use are called "mass" copper. Sometimes
+they weigh as much as five hundred tons.
+The copper in them is almost pure, and a big boulder
+is worth perhaps $200,000. Nevertheless, the
+mine-owners do not rejoice when they come upon
+such a mass in their digging, for it cannot be either
+dug or blasted, and has to be cut away with chisels
+of chilled steel. Now, a mine may be wonderfully
+rich in metal, but if working it costs too much, then
+another mine with less metal but more easily
+worked will pay better. So it is with these great
+masses of copper. They are interesting to study and
+they look well in museums, but they do not pay so
+well as the "stamp" copper which is found in humble
+little bits in the gangue, or the rock of the vein,
+and has to be pounded in a stamp mill. This gangue
+is dug out and broken up as in mines of other metals.
+The copper is much heavier than the rock, so it is
+easy to get rid of the worthless gangue by means of
+a flow of water. The gangue of the Michigan mines
+is exceedingly hard, but the stamps are so powerful
+that one can crush five hundred tons in less than
+twenty-four hours. Some copper can be taken out
+of the mortars at once, but the rest of the broken
+gangue is fed to jigs, or screens, which are kept
+under jets of water. The water is thrown up from
+below and the lighter rock is tossed away, while the
+heavier copper falls through the tiny holes in the
+screens.</p>
+<p><span class='pagenum'><a name="Page_67" id="Page_67">[Pg 67]</a></span></p>
+<p class="figcenter" style="width: 373px;">
+<img src="images/image068.jpg" width="373" height="580" alt="IN A COPPER SMELTER"
+ title="IN A COPPER SMELTER" />
+<span class="caption">IN A COPPER SMELTER<br /><br />
+
+The men are pouring hot copper into moulds for castings.</span>
+</p>
+
+<p><span class='pagenum'><a name="Page_68" id="Page_68">[Pg 68]</a></span></p>
+<p>After the ore has been through all these experiences,
+it comes out looking like dark-colored sand
+or coarse brown sugar. It is not interesting, and no
+one who saw it for the first time would ever fancy
+that it was going to turn into something beautiful.
+It is dumped into freight cars and trundled off to the
+smelting furnaces. But however uninteresting it
+looks, it is well worth while to follow these cars to
+see what happens to it at the smelters. First of all,<span class='pagenum'><a name="Page_69" id="Page_69">[Pg 69]</a></span>
+even before it goes into the smelting furnace, it must
+be roasted. There is usually sulphur combined with
+the copper, and roasting will get rid of much of it.
+In some places this is done by building up a great
+heap of ore with a little wood. The wood is kindled,
+and by the time it has burned out, the sulphur in
+the ore has begun to burn, and in a good-sized heap
+it will continue to burn for perhaps two months.</p>
+
+<p>Such a heap is a good thing to keep away from,
+for the fumes of sulphur are very disagreeable. Indeed,
+they will kill trees and other growing things
+wherever the wind may carry them, even several
+miles away. The managers of mines of copper as
+well as of gold and silver have learned to economize;
+and it has been found that instead of letting these
+fumes go into the air, they may be made to pass
+through acid chambers lined with zinc and full of
+water. The water holds the fumes, and can be used
+in making sulphuric acid.</p>
+
+<p>After the ore has been roasted, it is put into the
+furnace for smelting. If you should make an oven
+and put into it a mixture of wood and roasted copper,
+that would be a smelting furnace. Set the wood on
+fire, pump in air to make the flame hot, and if your
+furnace could be made hot enough,&mdash;that is, 2300&deg;
+F., or about eleven times as hot as boiling water,&mdash;you
+could smelt copper. Of course the furnace of a
+real smelting factory will hold tons and tons of
+copper ore and has all sorts of improvements, but
+after all it is in principle only an oven with wood
+and ore and draft. Another sort of furnace, which is<span class='pagenum'><a name="Page_70" id="Page_70">[Pg 70]</a></span>
+better for some kinds of ore, has a grate for the fire
+and a bed above it for the copper.</p>
+
+<p>Imagine an enormous furnace holding between
+two and three hundred tons of metal and burning
+with such a terrific heat that by contrast boiling
+water would seem cool and comfortable. Suddenly,
+while you stand looking at it, but a long way off, a
+door flies open and the most beautiful cascade&mdash;only
+it is not a waterfall, but a <i>copper</i> fall&mdash;pours
+out. It looks like red, red gold, rich and wonderful,
+with little flames of red and blue dancing over it.
+It might almost be one of the fire-breathing dragons
+of the old story-books; and if it should get loose, it
+would devour whomever it touched far quicker than
+any dragon. It hardly seems as if any one could
+manage such a monster; but it looks easy, after you
+have seen it done. An enormous horizontal wheel
+revolves slowly. On its edge are moulds shaped like
+bricks, but much larger. On the hub of the wheel a
+workman sits to direct the filling of these. A set
+of them is filled, and moves on, and others take their
+place. When they are partly cooled, another workman,
+at the farther side of the wheel, pries them out
+of the mould and drops them into water. Then by
+the aid of the fingers of a machine and those of men,
+they are loaded upon cars.</p>
+
+<p>In copper there is often some gold and silver. The
+precious metals do not make the copper any better,
+and if they can be separated from it, they are well
+worth the trouble. This is done by electricity. It is
+so successful that the metallurgists are hoping soon<span class='pagenum'><a name="Page_71" id="Page_71">[Pg 71]</a></span>
+to take a long step ahead and by means of electricity
+to produce refined copper directly from the ore.
+Indeed, this has been done already in the laboratories,
+but before the managers of mines can employ
+the method, a way of making it less expensive must
+be discovered.</p>
+
+<p>No mine that wastes anything is as well managed
+as it might be; and superintendents are constantly
+on the watch for cheaper methods and for ways to
+make the refuse matter of use. Even the scoria, or
+slag from the furnaces, has been found to be good
+for something, and now it is made into a coarse sort
+of brick that for certain rough uses is of value. By
+the way, the shaft of a copper mine, the Red Jacket,
+has shown itself of use in a manner that no one
+expected, namely, it helps to prove that the earth
+turns around. This shaft is the deepest mining shaft
+in the world, and when you get into the cage, you
+go down a full mile toward the center of the earth.
+If you drop any article into the shaft, it always
+strikes the east side before reaching the bottom.
+The only way to explain this is that the earth turns
+toward the east.</p>
+
+<p>Copper mixed with zinc forms brass, which is
+harder than copper alone. It tarnishes, though not
+so easily as copper; but a coat of varnish will protect
+it till the varnish wears off. A good way to find
+out the many uses of brass and to see how valuable
+they are is to go along the street and through a
+house and make a list. On the street you will see
+signs, harness buckles, and buttons, everywhere.<span class='pagenum'><a name="Page_72" id="Page_72">[Pg 72]</a></span>
+Look on the automobiles and fire engines for a fine
+display of brass, polished and shining. In the house
+you will find brass bedsteads, curtain rods, faucets,
+pipes, drawerpulls, candlesticks, gas and electric
+fixtures, lamps, the works of clocks and watches,
+and scores of other things. You will not have any
+idea how many they are till you begin to count.</p>
+
+<p>Copper mixed with tin forms bronze. Go into a
+hardware store and look at the samples of bronze
+outside of each drawer, and you will be surprised
+that there are so many. Bronze does not change
+even when in the open air for ages. That is one
+reason why it has always been so much used for
+statues. There are two strange facts about this mixture.
+One is that bronze is harder than either copper
+or tin. The other is that if you mix one pint of
+melted copper with one pint of tin, the mixture will
+be less than a quart. Just why these things are so,
+no one is quite certain. Mathematics declares that
+the whole is equal to the sum of its parts; but in
+this one case the whole seems to be less than the
+sum of its parts.</p>
+
+<p>Another reason why bronze is so much used for
+statues is that the castings are smooth. I once went
+to a foundry to have a brass ornament shaped somewhat
+like a cone made for a clock. The foundryman
+formed a mould in clay and poured the melted brass
+into it. When it had cooled, the mould was broken
+off and the ornament taken out; but it was of no use
+because it was so full of little hollows that it could
+not be made smooth without cutting away a great<span class='pagenum'><a name="Page_73" id="Page_73">[Pg 73]</a></span>
+deal of it. The man had to try three times before he
+succeeded in making one that could be polished. If
+it had been made of bronze, there would have been
+no trouble, because bronze, hard as it is after it
+cools, flows when it is melted almost as easily as
+molasses and fills every little nook and corner of the
+mould.</p>
+
+<p>A famous Latin poet named Horace, who lived two
+thousand years ago, wrote of his poems, "I have
+reared a monument more lasting than bronze";
+and he was right, for few statues have endured from
+his day to ours, but his poems are still read and
+admired.</p>
+
+<p>Bells are made of bronze, about three quarters
+copper and one quarter tin. It is thought that much
+copper gives a deep, full tone, and that much tin
+with, sometimes, zinc makes the tone sharp. The age
+of a bell has something to do with its sound being
+rich and mellow; but the bellmaker has even more,
+for he must understand not only how to cast it, but
+also how to tune it. If you tap a large bell, it will, if
+properly tuned, sound a clear note. Tap it just on
+the curve of the top, and it will give a note exactly
+one octave above the first. If the note of the bell is
+too low, it can be made higher by cutting away a
+little from the inner rim. If it is too high, it can be
+made lower by filing on the inside a little above the
+rim. Many of the old bells contain the gifts of silver
+and gold which were thrown in by people who
+watched their founding. The most famous bell in
+the United States is the "Liberty Bell" of Independence<span class='pagenum'><a name="Page_74" id="Page_74">[Pg 74]</a></span>
+Hall, in Philadelphia, which rang when
+Independence was adopted by Congress. This was
+founded in England long before the Revolution and
+later was melted and founded again in the United
+States.</p>
+
+<p>It would not be easy to get on without brass and
+bronze; but even these alloys are not so necessary as
+copper by itself. It is so strong that it is used in
+boiler tubes of locomotives, as roofing for buildings
+and railroad coaches, in the great pans and vats of
+the sugar factories and refineries. A copper ore
+called "malachite," which shows many shades of
+green, beautifully blended and mingled, is used for
+the tops of tables. Wooden ships are often "copper-bottomed";
+that is, sheets of copper are nailed to
+that part of the hull which is under water in order
+to prevent barnacles from making their homes on it,
+and so lessening the speed of the vessel.</p>
+
+<p>People often say that the latter half of the nineteenth
+century was the Age of Steel, because so
+many new uses for steel were found at that time.
+The twentieth century promises to be the Age of
+Electricity, and electricity must have copper. Formerly
+iron was used for telegraph wires; but it needs
+much more electricity to carry power or light or heat
+or a telegraphic message over an iron wire than one
+of copper. Moreover, iron will rust and will not
+stretch in storms like copper, and so needs renewing
+much oftener. Electric lighting and the telephone
+are everywhere, even on the summits of mountains
+and in mines a mile below the earth's surface. Electric<span class='pagenum'><a name="Page_75" id="Page_75">[Pg 75]</a></span>
+power, if a waterfall furnishes the electricity,
+is the cheapest power known. The common blue
+vitriol is one form of copper, and to this we owe
+many of our electric conveniences. It is used in all
+wet batteries, and so it rings our doorbells for us.
+It also sprays our apple and peach trees, and is a
+very valuable article. Indeed, copper in all its forms,
+pure and alloyed, is one of our best and most helpful
+friends.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_76" id="Page_76">[Pg 76]</a></span></p>
+<h2><a name="IX" id="IX"></a>IX</h2>
+
+<h3>THE NEW METAL, ALUMINUM</h3>
+
+
+<p>Not many years ago a college boy read about an
+interesting metal called "aluminum." It was as
+strong as iron, but weighed only one third as much,
+and moisture would not make it rust. It was made
+of a substance called "alumina," and a French
+chemist had declared that the clay banks were full
+of it; and yet it cost as much as silver. It had been
+used in France for jewelry and knicknacks, and a
+rattle of it had been presented to the baby son of
+the Emperor of France as a great rarity.</p>
+
+<p>The college boy thought by day and dreamed by
+night of the metal that was everywhere, but that
+might as well be nowhere, so far as getting at it was
+concerned. At the age of twenty-one, the young
+man graduated, but even his new diploma could not
+keep his mind away from aluminum. He borrowed
+the college laboratory and set to work. For seven
+or eight months he tried mixing the metal with
+various substances to see if it would not dissolve.
+At length he tried a stone from Greenland called
+"cryolite," which had already been used for making
+a kind of porcelain. The name of this stone comes
+from two Greek words meaning "ice stone," and it is
+so called because it melts so easily. The young student
+melted it and found that it would dissolve
+alumina. Then he ran an electric current through<span class='pagenum'><a name="Page_77" id="Page_77">[Pg 77]</a></span>
+the melted mass, and there was a deposit of aluminum.
+This young man, just out of college, had discovered
+a process that resulted in reducing the cost
+of aluminum from twelve dollars a pound to eighteen
+cents. Meanwhile a Frenchman of the same age
+had been working away by himself, and made the
+same discovery only two months later.</p>
+
+<p>Aluminum is now made from a mineral called
+"bauxite," found chiefly in Georgia, Alabama, and
+Arkansas. Mining it is much more agreeable than
+coal mining, for the work is done aboveground.
+The bauxite is in beds or strata which often cover
+the hills like a blanket. First of all, the mine is
+"stripped,"&mdash;that is, the soil which covers the ore
+is removed,&mdash;and then the mining is done in great
+steps eight or ten feet high, if a hill is to be worked.
+There is some variety in mining bauxite, for it occurs
+in three forms. First, it may be a rock, which has to
+be blasted in order to loosen it. Second, it may be
+in the form of gray or red clay. Third, it occurs in
+round masses, sometimes no larger than peas, and
+sometimes an inch in diameter. In this form it can
+easily be loosened with a pickaxe, and shoveled into
+cars to be carried to the mill. Bauxite is a rather
+mischievous mineral and sometimes acts as if it
+delighted in playing tricks upon managers of mines.
+The ore may not change in the least in its appearance,
+and yet it may suddenly have become much
+richer or much poorer. Therefore the superintendent
+has to give his ore a chemical test every little while
+to make sure that all things are going on well.<span class='pagenum'><a name="Page_78" id="Page_78">[Pg 78]</a></span></p>
+
+<p>This bauxite is purified, and the result is a fine
+white powder, which is pure alumina, and consists of
+the metal aluminum and the gas oxygen. Cryolite
+is now melted by electricity. The white powder is
+put into it, and dissolves just as sugar dissolves in
+water. The electricity keeps on working, and now
+it separates the alumina into its two parts. The
+aluminum is a little heavier than the melted cryolite,
+and therefore it settles and may be drawn off at
+the bottom of the melting-pot.</p>
+
+<p>There are a good many reasons why aluminum is
+useful. As has been said it is strong and light and
+does not rust in moisture. You can beat it into
+sheets as thin as gold leaf, and you can draw it into
+the finest wire. It is softer than silver, and it can be
+punched into almost any form. It is the most
+accommodating of metals. You can hammer it in
+the cold until it becomes as hard as soft iron. Then,
+if you need to have it soft again, it will become so by
+melting. It takes a fine polish and is not affected,
+as silver is, by the fumes which are thrown off by
+burning coal; and so keeps its color when silver
+would turn black. Salt water does not hurt it in the
+least, and few of the acids affect it. Another good
+quality is that it conducts electricity excellently.
+It is true that copper will do the same work with a
+smaller wire; but the aluminum is much lighter and
+so cheap that the larger wire of aluminum costs less
+than the smaller one of copper, and its use for this
+purpose is on the increase. It conducts heat as well
+as silver. If you put one spoon of aluminum, one of
+silver, and one that is "plated" into a cup of hot
+water, the handles of the first two will almost burn
+your fingers before the third is at all uncomfortable
+to touch.</p>
+<p><span class='pagenum'><a name="Page_79" id="Page_79">[Pg 79]</a></span></p>
+<p class="figcenter" style="width: 556px;">
+<img src="images/image080.jpg" width="556" height="600" alt="A &quot;MOVIE&quot; OF AN ALUMINUM FUNNEL"
+ title="A &quot;MOVIE&quot; OF AN ALUMINUM FUNNEL" />
+<span class="caption">A "MOVIE" OF AN ALUMINUM FUNNEL<br /><br />
+
+<i><small>Courtesy The Aluminum Cooking Utensil Company.</small></i><br /><br />
+
+Seventeen other operations are necessary after the thirteenth stamping
+operation before the funnel is ready to be sold. And after all this
+work, we can buy it for 35 cents at any hardware store.</span>
+</p>
+
+<p><span class='pagenum'><a name="Page_80" id="Page_80">[Pg 80]</a></span></p>
+<p>Aluminum is found not only in clay and indeed in
+most rocks except sandstone and limestone, but also
+in several of the precious stones, in the yellow topaz,
+the blue sapphire and lapis-lazuli, and the red garnet
+and ruby. It might look down upon some of its
+metallic relatives, but it is friendly with them all,
+and perfectly willing to form alloys with most of
+them. A single ounce of it put into a ton of steel as
+the latter is being poured out will drive away the
+gases which often make little holes in castings.
+Mixed with copper it makes a beautiful bronze
+which has the yellow gleam of gold, but is hard to
+work. When a piece of jewelry looks like gold, but
+is sold at too low a price to be "real," it may be aluminum
+bronze, very pretty at first, but before long its
+luster will vanish. Aluminum bronze is not good for
+jewelry, but it is good for many uses, especially for
+bearings in machinery. Aluminum mixed with even
+a very little silver has the color and brightness of
+silver. The most common alloys with aluminum are
+zinc, copper, and manganese, but in such small
+quantities that they do not change its appearance.</p>
+
+<p>With so many good qualities and so few bad ones,
+it is small wonder that aluminum is employed for
+more purposes than can be counted. A very few
+years ago it was only an interesting curiosity, but
+now it is one of the hardest-worked metals. Automobiles<span class='pagenum'><a name="Page_81" id="Page_81">[Pg 81]</a></span>
+in particular owe a great deal to its help.
+When they first began to be common, in 1904-05,
+the engines were less powerful than they are now
+made, and aluminum was largely employed in order
+to lessen the weight. Before long it was in use for
+carburetors, bodies, gear-boxes, fenders, hoods, and
+many other parts of the machine. Makers of electric
+apparatus use aluminum instead of brass. The
+frames of opera glasses and of cameras are made of
+it. Travelers and soldiers and campers, people to
+whom every extra ounce of weight counts, are glad
+enough to have dishes of aluminum. The accommodating
+metal is even used for "wallpaper," and
+threads of it are combined with silk to give a specially
+brilliant effect on the stage. It can be made
+into a paint which will protect iron from rust; and
+will make woodwork partially fireproof.</p>
+
+<p>Aluminum has been gladly employed by the manufacturers
+of all sorts of articles, but nowhere has
+its welcome been more cordial than in the kitchen.
+Any one who has ever lifted the heavy iron kettles
+which were in use not so very many years ago will
+realize what an improvement it is to have kettles
+made of aluminum. But aluminum has other advantages
+besides its lightness. If any food containing a
+weak acid, like vinegar and water, is put into a copper
+kettle, some of the copper dissolves and goes
+into the food; acid does not affect aluminum except
+to brighten it if it has been discolored by an alkali
+like soda. "Tin" dishes, so called, are only iron
+with a coating of tin. The tin soon wears off, and<span class='pagenum'><a name="Page_82" id="Page_82">[Pg 82]</a></span>
+the iron rusts; aluminum does not rust in moisture.
+A strong alkali will destroy it, but no alkali in common
+use in the kitchen is strong enough to do more
+harm than to change the color, and a weak acid will
+restore that. Enameled ware, especially if it is
+white, looks dainty and attractive; but the enamel is
+likely to chip off, and, too, if the dish "boils dry,"
+the food in it and the dish itself are spoiled. Aluminum
+never chips, and it holds the heat in such a
+manner as to make all parts of the dish equally hot.
+Food, then, is not so likely to "burn down," but if it
+does, only the part that sticks will taste scorched;
+and no matter how many times a dish "boils dry,"
+it will never break. If you make a dent in it, you
+can easily pound it back into shape again. It is said
+that an aluminum teakettle one sixteenth of an inch
+in diameter can be bent almost double before it will
+break.</p>
+
+<p>Aluminum dishes are made in two ways. Sometimes
+they are cast, and sometimes they are drawn
+on a machine. If one is to be smaller at the top, as
+in the case of a coffeepot, it is drawn out into a cylinder,
+then put on a revolving spindle. As it whirls
+around, a tool is held against it wherever it is to
+be made smaller, and very soon the coffeepot is in
+shape. The spout is soldered on, but even the solder
+is made chiefly of aluminum.</p>
+
+<p>Aluminum dishes may become battered and
+bruised, but they need never be thrown away.
+There is an old story of some enchanted slippers
+which brought misfortune to whoever owned them.<span class='pagenum'><a name="Page_83" id="Page_83">[Pg 83]</a></span>
+The man who possessed them tried his best to get
+rid of the troublesome articles, but they always returned.
+So it is with an aluminum dish. Bend it,
+burn it, put acid into it, do what you will to get rid
+of it, but like the slippers it remains with you.
+Unlike them, however, it brings good fortune, because
+it saves time and trouble and patience and
+money.</p>
+
+<p>A few years ago the motive power for most manufactures
+was steam. Electricity is rapidly taking its
+place; and if aluminum was good for nothing else
+save to act as a conductor of electricity in its various
+applications, there would even then be a great future
+before it.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_84" id="Page_84">[Pg 84]</a></span></p>
+<h2><a name="X" id="X"></a>X</h2>
+
+<h3>THE OIL IN OUR LAMPS</h3>
+
+
+<p>Probably the first man who went to a spring for
+a drink and found oil floating on the water was decidedly
+annoyed. He did not care in the least where
+the oil came from or what it was good for; he was
+thirsty, and it had spoiled his drink, and that was
+enough for him. We know now that oil comes
+chiefly from strata of coarse sandstone, but we are
+not quite sure how it happened to be there. The sand
+which formed these strata was deposited by water
+ages and ages ago&mdash;we are certain of that. Another
+thing that we are certain of is that where the
+strata lie flat, there is no oil. Hot substances become
+smaller as they cool; and as the earth grew
+cooler, it became smaller. The crust of the earth
+wrinkled as the skin of an apple does when it dries.
+In the tops of these great sandstone wrinkles there
+is often gas; and below the gas is the place where oil
+is found. There is no use in looking for petroleum
+where the folds of the strata are very sharp, because
+in that case the strata crack and let the oil
+flow away. It is not in pools, but the porous stone
+holds it just as a sponge holds water. If you drop a
+little oil upon a stone even much less porous than
+sandstone, it will not be easy to wipe it off, because
+some of it will have sunk into the stone.</p>
+
+<p>In many places the gas forces its way out, and is<span class='pagenum'><a name="Page_85" id="Page_85">[Pg 85]</a></span>
+piped to carry to houses for light and heat. Not far
+above Niagara Falls there was a spring of gas which
+flowed for years. An iron pipe was put down, and
+when the gas was lighted, the flame shot up three
+or four feet. The gas came with such force that a
+handkerchief put over the end of the pipe would not
+burn, though the flame would blaze away above it.
+In the country of the fire worshipers, on the shores
+of the Caspian Sea, fires of natural gas have been
+burning for ages, kindled, perhaps, by lightning centuries
+ago. There is a vast supply of oil in this place;
+and indeed there is hardly a country that has not
+more or less of it.</p>
+
+<p>In the United States the colonists soon learned
+that there was petroleum in what is now the State
+of New York; but New York was a long way from
+the Atlantic seaboard in those days, and they went
+on contentedly burning candles or sperm whale oil,
+or, a little later, a rather dangerous liquid which was
+known as "fluid." The Indians believed that the oil
+which appeared in the springs was a good medicine.
+They threw their blankets upon the water, and when
+these had become saturated with the oil, they
+wrung them out and sold the oil. Those were the
+times when if a medicine only tasted and smelled
+bad enough, people never doubted that it would
+cure all their diseases, and they gladly bought the
+oil of the Indians.</p>
+
+<p>When at last it became clear to the members of
+an enterprising company that oil for use in lamps
+could be made from petroleum, they secured some<span class='pagenum'><a name="Page_86" id="Page_86">[Pg 86]</a></span>
+land in Pennsylvania that seemed promising and
+set to work to dig a well. But the more they dug,
+the more the loose dirt fell in upon them. Fortunately
+for the company, the superintendent had
+brains, and he thought out a way to get the better
+of the crumbling soil. He simply drove down an iron
+pipe to the sandstone which contained the oil, and
+set his borer at work within the pipe. One morning
+he found that the oil had gushed in nearly to the top
+of the well. He had "struck oil."</p>
+
+<p>This was about ten years after the rush to California
+for gold, and now that this cheaper and
+quicker method of making a well had been invented,
+there was almost as much of a rush to Pennsylvania
+for oil. With every penny that they could beg or
+borrow, people from the East hurried to the westward
+to buy or lease a piece of land in the hope of
+making their fortunes. A song of the day had for its
+refrain,&mdash;</p>
+
+<div class="poem"><div class="stanza">
+<span class="i0">"Stocks par, stocks up,<br /></span>
+<span class="i2">Then on the wane;<br /></span>
+<span class="i0">Everybody's troubled with<br /></span>
+<span class="i2">Oil on the brain."<br /></span>
+</div></div>
+
+<p>In the course of a year or two, the first "gusher"
+was discovered. The workmen had drilled down
+some four or five hundred feet and were working
+away peacefully, when a furious stream of oil burst
+forth which hurled the tools high up into the air.
+Hundreds of barrels gushed out every day, and
+soon other gushers were discovered. The most famous
+one in the world is at Lakeview, California.
+For months it produced fifty thousand barrels of oil
+a day, and threw it up three hundred and fifty feet
+into the air in a black column, spraying the country
+with oil for a mile around. The oil flowed away in
+a river, and for a time no one could plan any way to
+stop it or store it. At last, however, a mammoth
+tank was built around the well and made firm with
+stones and bags of earth. This was soon full of oil;
+and with all this vast weight of oil pressing down
+upon it, the stream could not rise more than a few
+feet above the surface. Just why oil should come out
+with such force, the geologists are not quite certain;
+but it is thought to result from a pressure of gas
+upon the sandstone containing it. The flow almost
+always becomes less and less, and after a time the
+most generous well has to be pumped.</p>
+<p><span class='pagenum'><a name="Page_87" id="Page_87">[Pg 87]</a></span></p>
+<p class="figcenter" style="width: 800px;">
+<img src="images/image088.jpg" width="800" height="413" alt="A CALIFORNIA OIL FIELD"
+ title="A CALIFORNIA OIL FIELD" />
+<span class="caption">A CALIFORNIA OIL FIELD<br /><br />
+
+For scenery, one should not go to an oil field. Looks, smell, and oil
+alike are unpleasant, but every oil derrick covers a fortune and helps
+to make our machinery run smoothly.</span>
+</p>
+
+<p><span class='pagenum'><a name="Page_88" id="Page_88">[Pg 88]</a></span></p>
+<p>An "oil field" may extend over thousands of
+square miles; but within this field there are always
+"pools"; that is, certain smaller fields, where oil is
+found. When a man thinks there is oil in a certain
+spot, sometimes he buys the land if he is able; but
+oftener he gets permission of the owner to bore a
+well, agreeing to pay him a royalty; that is, a certain
+percentage of all the oil that is produced.
+When this has been arranged, he builds his derrick.
+This consists of four strong upright beams firmly
+held together by crossbeams. It stands directly
+over the place where the well is to be dug. It is from
+thirty to eighty feet in height, according to the
+depth at which it is hoped to find oil. There must
+also be an engine house to provide the power for<span class='pagenum'><a name="Page_89" id="Page_89">[Pg 89]</a></span>
+drilling. An iron pipe eight or ten inches in diameter
+is driven down through the soil until it comes to
+rock. Now the regular drilling begins. At the top
+of the derrick is a pulley. Over the pulley passes a
+stout rope to which the heavy drilling tools&mdash;the
+"string of tools," as they are called&mdash;are fastened.
+The drilling goes on day and night. The drill makes
+the hole, and the sand pump sucks out the water and
+loose bits of stone. When the drill has gone to the
+bottom of the strata which carry water, the sides of
+the bore are cased to keep the water out; then the
+drilling continues, but now the drill makes its way
+into the oil-bearing sandstone.</p>
+
+<p>There is nothing certain about the search for oil.
+In some places it is near the surface, in others it is
+perhaps three or four thousand feet down. The well
+may prove to be a gusher and pour out hundreds of
+thousands of gallons a day; or the oil may refuse to
+rise to the surface and have to be pumped out even
+at the first. Naturally, no one is prepared for a
+gusher, and millions of gallons have often flowed
+away before any arrangements could be made for
+storing the oil. Sometimes a well that gives only a
+moderate flow can be made to yield generously by
+exploding a heavy charge of dynamite at the bottom,
+to break up the rock and, it is always hoped,
+to open some new oil-holding crevice that the drill
+has not reached.</p>
+
+<p>Crude petroleum is a dark, disagreeable, bad-smelling
+liquid; and before it can be of much use, it
+must be refined. For several years it was carried in<span class='pagenum'><a name="Page_90" id="Page_90">[Pg 90]</a></span>
+barrels from the oil fields to Pittsburgh by wagon
+and boat, a slow, expensive process, and generally
+unsatisfactory to all but the teamsters. Then came
+the railroads. They provided iron tanks in the shape
+of a cylinder fastened to freight cars, much like those
+employed to-day. There was only one difficulty
+about sending oil by rail, and that was that it still
+had to be hauled by team to the railroad, sometimes
+a number of miles. At length, some one said to himself,
+"Why cannot we simply run a pipe directly
+from the well to the railroad?" This was done.
+Pumping engines were put in a few miles apart, and
+the invention was a success in the eyes of all but the
+teamsters. In spite of their opposition, however,
+pipe-lines increased.</p>
+
+<p>Before this it had been necessary to build the refineries
+as near the oil regions as possible in order to
+save the expense of carrying the oil; but now they
+could be built wherever it was most convenient.
+To-day oil can be brought at a small expense from
+west of the Mississippi River to the Atlantic seaboard,
+refined, and distributed throughout that
+part of the country, or loaded into "tankers,"&mdash;that
+is, steamships containing strong tanks of steel,&mdash;and
+so taken across the ocean. The pipes are
+made of iron and are six or eight inches or more in
+diameter. In using them one difficulty was found
+which has been overcome in an ingenious fashion.
+Sometimes they become choked by the impurities of
+the oil and the flow is lessened. Then a "go-devil"
+is put into them. This is shaped like a cartridge, is<span class='pagenum'><a name="Page_91" id="Page_91">[Pg 91]</a></span>
+about three feet in length, composed of springs and
+plates of iron and so flexible that it can turn around
+a corner. It is so made that as it slips down the current
+of oil, it whirls around and in so doing its nose
+of sharp blades scrapes the pipes clean.</p>
+
+<p>The pipes go over hills and through swamps.
+They cross rivers sometimes by means of bridges,
+and sometimes they are anchored to the bed of the
+stream. If they have to go through a salt marsh,
+they are laid in concrete to preserve the iron. If
+these lines were suddenly destroyed and oil had to
+be carried in the old way, kerosene would become an
+expensive luxury.</p>
+
+<p>Getting the oil out of the ground and carried to
+the refineries is not all of the business by any means.
+The early oils crusted on the lamp wicks, their smell
+was unendurable, and they were given to exploding.
+Evidently, if oil was to be used for lighting, it must
+be improved, and the first step was to distil it. To
+distil anything means to boil it and collect the vapor.
+If you hold a piece of cold earthenware in the steam
+of a teakettle, water will collect on it. This is distilled
+water, and is purer than that in the kettle.
+Petroleum was at first distilled in a rough way; but
+now it is done with the utmost care and exactness.
+The crude oil is pumped into boilers holding six hundred
+barrels or more. The fires are started, and the oil
+soon begins to turn into vapor. This vapor passes
+through coils of pipe or long, straight, parallel pipes.
+Cold water is pumped over these pipes, the vapor
+turns into a liquid again, and we have kerosene oil.<span class='pagenum'><a name="Page_92" id="Page_92">[Pg 92]</a></span></p>
+
+<p>This is the outline of the process, but it is a small
+part of the actual work in all its details. Kerosene
+oil is only one of the many substances found in petroleum.
+Fortunately, some of these substances are
+light, like gasoline and benzine; some, like kerosene,
+are heavier; and paraffin and tar are heaviest of all.
+There are also gases, which pass off first and are
+saved to help keep the furnace going. Then come the
+others, one by one, according to their weight. The
+stillman keeps close watch, and when the color and
+appearance of the distillate changes, he turns it off
+into another tank. This process is called "fractional
+distillation," and the various products are called
+"fractions." No two kinds of petroleum and no two
+oil wells are just alike, and it needs a skillful man
+to manage either.</p>
+
+<p>Even after all this distillation, the kerosene still
+chars the wick somewhat&mdash;which prevents the
+wick from drawing up the oil properly&mdash;and it still
+has a disagreeable smell. To fit it for burning in
+lamps, it must be treated with sulphuric acid,
+which carries away some of the impurities, and then
+with caustic soda, which carries away others. Before
+it can be put on the market, it is examined to
+see whether it is of the proper color. Then come
+three important tests. The first is to see that it is
+of the proper weight. If it is too heavy, it will not
+burn freely enough; if it is too light, then there is too
+much of the lighter oils in it for safety. The second
+test is the "flash test." The object of this is to see
+how hot the oil must be before it gives off a vapor<span class='pagenum'><a name="Page_93" id="Page_93">[Pg 93]</a></span>
+which will burn. The third, the "burning test," is to
+discover how hot the oil must be before it will take fire
+and burn on the surface. Most civilized countries
+make definite laws forbidding the sale of kerosene
+oil that is not up to a standard of safety. Oil for
+use in lamps should have an open flash test of at least
+100&deg; F. and a burning point of not less than 125&deg; F.</p>
+
+<p>We say that we burn oil in our lamps, but what
+we really do is to heat the oil until it gives off gas,
+and then we burn the gas. To keep the flame regular
+and help on the burning, we use a chimney on the
+lamp. The hot air rises in the chimney and the cold
+air underneath rushes in to take its place and brings
+oxygen to the flame. In a close, stuffy room no
+lamp will give a good clear light, because there is not
+oxygen enough for its flame. Let in fresh air, and
+the light will be brighter. If you hold a cold plate
+in the flame before the chimney is put on, soot or
+carbon will be deposited. A lamp gives light because
+these particles of carbon become so hot that they
+glow. In lamps using a "mantle," there is the glow
+not only of these particles, but also of the mantle.
+In a wax candle, we light the wick, its heat melts the
+wax and carries it to the flame. When the wax is
+made hot enough, it becomes gas, and we burn the
+gas, not the wax. Wax alone will melt, but not take
+fire even if a burning match is held to it. The reason
+is that the match does not give heat enough to turn
+the wax into gas. But put a bit of wax upon a bed
+of burning coals, where there is a good supply of
+heat, and it will turn into gas and burn.<span class='pagenum'><a name="Page_94" id="Page_94">[Pg 94]</a></span></p>
+
+<p>The products made from petroleum are as different
+in their character and uses as paraffin and
+naphtha. Some of them are used for oiling machinery;
+tar is used for dyes; naphtha dissolves resin to
+use in varnish; benzine is the great cleanser of
+clothes, printers' types, and almost everything else;
+gasoline runs automobiles, motors, and many sorts
+of engines; paraffin makes candles, seals jelly glasses,
+covers the heads of matches so that they are no
+longer spoiled by being wet, and makes the ever-useful
+"waxed paper"; printers' ink and waterproof
+roofing-paper both owe a debt to petroleum. Even
+in medicine, though a little petroleum is no longer
+looked upon as a cure-all, vaseline, one of its products,
+is of great value. It can be mixed with drugs
+without changing their character, and it does not
+become rancid. For these reasons, salves and other
+ointments can be mixed with it and preserved for
+years.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_95" id="Page_95">[Pg 95]</a></span></p>
+<h2><a name="XI" id="XI"></a>XI</h2>
+
+<h3>LITTLE GRAINS OF SALT</h3>
+
+
+<p>The most interesting mine in the world is that of
+Wieliczka in Poland. In it there are some thirty
+miles of streets and alleys; there are churches with
+pillars, shrines, and statues; there are stairs, monuments,
+and restaurants; there is a ballroom three
+hundred feet long and one hundred and ninety feet
+high, with beautiful chandeliers, and in it is a carven
+throne whereon the Emperor Franz Joseph sat when
+he visited the mine. There are lakes crossed by
+ferryboats. There is a railroad station for the mule
+trains which bear the precious mineral salt, for this
+is a salt mine, and shrines, statues, churches, chandeliers&mdash;everything&mdash;are
+all cut out of salt.</p>
+
+<p>This mine has been worked for at least eight hundred
+years and still has salt enough to supply all
+Europe for ages. The mass of salt is believed to be
+five hundred miles long, fifty miles wide, and nearly
+a quarter of a mile thick. It is so pure that it is sold
+just as it comes from the mine, either in blocks or
+finely ground. This mine is a wonderful place to
+visit, almost like an enchanted palace, for as the
+torchlight strikes the crystals of salt, they flash and
+sparkle as if the wall was covered with rubies and
+diamonds.</p>
+
+<p>There is nothing like an enchanted palace in any<span class='pagenum'><a name="Page_96" id="Page_96">[Pg 96]</a></span>
+salt mine of the United States, no statues or chapels
+or chandeliers. There is only a hole in the ground,
+where mining is carried on in much the same manner
+as in other kinds of mines. The shaft is sunk and
+lined with timbers to keep the dirt from falling in,
+just as in other mines. In working salt mines, however,
+water is almost as bad as earth, and therefore
+a layer of clay is put between the timbers and the
+earth. There are the usual galleries and pillars, with
+roof and floor of salt. The workmen try to get the
+salt out in lumps or blocks as far as possible, and
+so they bore in drill holes and then blast with dynamite
+or powder. The salt is loaded upon little cars,
+running on tracks, and is carried up the shaft and
+to the top of a breaker, usually more than one hundred
+feet above the surface of the ground. There it
+is dumped upon a screen of iron bars, which lets the
+fine salt fall through. The large lumps are sold without
+crushing or sifting, and are used for cattle and
+sheep.</p>
+
+<p>One of the great deposits of salt is in southeastern
+California. It is thought that the Gulf of California
+used to run much farther north than it now does,
+and that the earth rose, shutting away part of it
+from the ocean. This imprisoned water was full of
+salt. In time it dried, and the sand blew over it till
+it was far underground. A better way than digging
+was found to work it, as will be seen later; but while
+digging was going on, the workmen built a cottage
+of blocks of salt, clear and glassy. The little rain
+that falls there melted the blocks only enough to<span class='pagenum'><a name="Page_97" id="Page_97">[Pg 97]</a></span>
+unite them firmly together; and there the house has
+stood for many years.</p>
+
+<p>Countries that have no deposits of rock salt can
+easily get plenty of salt from the water of the ocean
+if they only have a seacoast. About one thirtieth of
+the ocean water is salt, and if the water is evaporated,
+the salt can be collected without difficulty.
+France makes a great deal of salt in this way. When
+a man goes into the manufacture, or rather, the collecting
+of salt, he first of all buys or rents a piece of
+land,&mdash;perhaps several acres of it,&mdash;that lies just
+above high water, and makes it as level as possible.
+Unless it is very firm land, he covers it with clay, so
+that the water will not soak through it. Then he
+divides it into large square basins, making each a
+little lower than the one before it. Close beside the
+highest basin he makes a reservoir which at high
+tide receives water from the ocean. This flows
+slowly from the reservoir through one basin after
+another, becoming more and more salt as the water
+evaporates. At length the water is gone, and the
+salt remains. The workmen take wooden scrapers
+and push the salt toward the walls of the basins and
+then shovel it up on the dikes and heap it into creamy
+cones that sparkle in the sunshine. The dikes are
+narrow, raised pathways beside the basins and between
+them. As you walk along on top of them, you
+can smell a faint violet perfume from the salt.
+Thatch is put over the cones to protect them from
+the rain, and there they stand till some of the impurities
+drain away. This salt is not perfectly white,<span class='pagenum'><a name="Page_98" id="Page_98">[Pg 98]</a></span>
+because the workmen cannot help scraping up a
+little of the gray or reddish clay with it. Most of it
+is sold as it is, nevertheless, for many people have
+an absurd notion that the darker it is the purer it is.
+For those who wish to buy white salt it is sent to a
+refinery to be washed with pure water, then boiled
+down and dried.</p>
+
+<p>So it is that the sun helps to manufacture salt. In
+some of the colder countries, frost does the same
+work, but in a very different manner. When salt
+water freezes, the <i>water</i> freezes, but the salt does
+not, and a piece of salt water ice is almost as pure as
+that made of fresh water. Of course, after part of
+the water in a basin of salt water has been frozen
+out, what is left is more salt than it was at first, and
+after the freezing has been repeated several times,
+only a little water remains, and evaporation will
+soon carry this away, leaving only salt in the basin,
+waiting to be purified.</p>
+
+<p>Not very many years ago one of the encyclop&aelig;dias
+remarked that "the deposits of salt in the United
+States are unimportant." This was true as far as the
+working of them was concerned, but in 1913 the
+United States produced more than 34,000,000 barrels.
+Part of this was made by evaporation of the
+waters of salt springs, and a small share from Great
+Salt Lake in Utah. The early settlers in Utah used
+to gather salt from the shallow bays or lagoons
+where the water evaporated during the summer;
+but now dams of earth hold back the water in a
+reservoir. In the spring the pumps are put to work<span class='pagenum'><a name="Page_99" id="Page_99">[Pg 99]</a></span>
+and the reservoir is soon filled with water. This is
+left to stand and give the impurities a chance to
+settle to the bottom. Then it is allowed to flow into
+smaller basins, while more water is pumped into the
+reservoir. When autumn comes, the crop of salt is
+ready to be harvested. It is in the form of a crust
+three to six inches thick, some of it in large crystals,
+and some fine-grained. This crust is broken by
+ploughs, and the salt is heaped up into great cones
+and left for the rain to wash clean. Then it goes to
+the mill for purifying. The water of Great Salt Lake
+is much more salty than that of the ocean. It preserves
+timber remarkably well, and often salt from
+the lake is put around telephone poles, seventy-five
+pounds being dropped into the hole for each one. It
+has been suggested to soak timber in the Lake, and
+then paint it with creosote to keep the wet out and
+the salt in.</p>
+
+<p>Salt is also made from the waters of salt springs,
+which the Indians thought were the homes of evil
+spirits. At Salton, in California, an area of more
+than one thousand acres, which lies two hundred
+and sixty-four feet below sea level, is flooded with
+water from salt springs. When this water has evaporated,
+all these acres are covered with salt ten to
+twenty inches thick, and as dazzlingly white as if it
+was snow. This great field is ploughed up with a
+massive four-wheeled implement called a "salt-plough."
+It is run by steam and needs two men to
+manage it. The heavy steel ploughshare breaks up
+the salt crust, making broad, shallow furrows and<span class='pagenum'><a name="Page_100" id="Page_100">[Pg 100]</a></span>
+throwing the salt in ridges on both sides. The plough
+has hardly moved on before the crust begins to form
+again. This broken crust is worked in water by men
+with hoes in order to remove the bits of earth that
+stick to it, then piled up into cones to drain, loaded
+upon flat trucks, and carried to the breaker. The
+salt fields are wonderfully beautiful in the moonlight,
+but not very agreeable to work in, for the mercury
+often reaches 140&deg; F., and the air is so full of
+particles of salt that the workers feel an intense
+thirst, which the warm, brackish water does not
+satisfy. The work is done by Indians and Japanese,
+for white people cannot endure the heat.</p>
+
+<p>A large portion of the salt used in the United
+States comes directly from rock salt strata, hundreds
+of feet below the surface of the ground. These were
+perhaps the bed of the ocean ages and ages ago.
+There is a great extent of the beds in New York,
+Michigan, Ohio, Kansas, and other States. In
+Michigan there is a stratum of rock salt thirty to
+two hundred and fifty feet thick and some fifteen
+hundred to two thousand feet below the surface.
+To mine this would be a difficult and expensive
+undertaking, and a far better way has been discovered.
+First, a pipe is forced down through the surface
+dirt, the limestone, and the shale to the salt
+stratum. The drill works inside this pipe and bores
+a hole for a six-inch pipe directly into the salt. A
+three-inch pipe is let down inside of the six-inch
+pipe, and water is forced down through the smaller
+pipe. It dissolves the salt, becomes brine, and rises<span class='pagenum'><a name="Page_101" id="Page_101">[Pg 101]</a></span>
+through the space between the two pipes. It is carried
+through troughs to some great tanks, and from
+these it flows into "grain-settlers," then into the
+"grainers" proper, where the grains of salt settle.
+At the bottom of the grainers are steam pipes, and
+these make the brine so hot that before long little
+crystals of salt are seen floating on the surface of the
+water. Crystals form much better if the water is
+perfectly smooth, and to bring this about a very
+little oil is poured into the grainer. It spreads over
+the surface in the thinnest film that can be imagined.
+The water evaporates, and the tiny crystals grow,
+one joining to another as they do in rock candy.
+When they become larger, they drop to the bottom
+of the grainer. They are now swept along in a trough
+to a "pocket," carried up by an endless chain of
+buckets, and then wheeled away to the packinghouse.</p>
+
+<p>The finest salt is made by using vacuum pans.
+These are great cans out of which the air is pumped,
+and into which the brine flows. This brine, heated
+by steam pipes, begins to boil, and as the steam from
+it rises, it has to pass through a pipe at the top and
+is thus carried into a small tank into which cold
+water is flowing. The cold makes the steam condense
+into water, which runs off. The condensed
+water occupies less space than the steam and so
+maintains the vacuum in the pan. For a perfect
+vacuum the brine is boiled at less than 100&deg; F.,
+while in an open pan or grainer it requires 226&deg; to
+boil brine. The brine is soon so rich in salt that tiny<span class='pagenum'><a name="Page_102" id="Page_102">[Pg 102]</a></span>
+crystals begin to form. These are taken out and
+dried. If you look at some grains of table salt
+through a magnifying glass, you can see that each
+grain is a tiny cubical crystal. Sometimes two or
+three are united, and often the corners are rounded
+off and worn, but they show plainly that they are
+little cubes.</p>
+
+<p>Most of the salt used on our tables is made by the
+vacuum process or by an improved method which
+produces tiny flakes of salt similar to snowflakes.
+The salt brine is heated to a high temperature and
+filtered. In the filters the impurities are taken out,
+and this process gives us very pure salt. The tiny
+flakes dissolve more easily than the cubes of salt,
+and thus flavor food more readily.</p>
+
+<p>With a few savage tribes salt is regarded as a
+great luxury, but with most peoples it is looked upon
+as a necessity. Some of the early races thought a
+salt spring was a special gift of the gods, and in their
+sacrifices they always used salt. In later times to sit
+"above the salt," between the great ornamental salt
+cellar and the master of the house, was a mark of
+honor. Less distinguished guests were seated "below
+the salt." To "eat a man's salt" and then be unfaithful
+to him has always been looked upon as a
+shameful act; and with some of the savages, so long
+as a stranger "ate his salt,"&mdash;that is, was a guest
+in the house of any one of them,&mdash;he was safe. To
+"eat salt together" is an expression of friendliness.
+Cakes of salt have been used as money in various
+parts of Africa and Asia. "Attic salt" means wit,<span class='pagenum'><a name="Page_103" id="Page_103">[Pg 103]</a></span>
+because the Athenians, who lived in Attica, were
+famous for their keen, delicate wit. To take a story
+or a statement "with a grain of salt" means not to
+accept it entirely, but only to believe it partially.
+When Christ told his disciples that they were "the
+salt of the earth," he meant that their lives and
+teaching would influence others just as salt affects
+every article of food and changes its flavor. Our
+word "salary" comes from the Latin word <i>sal</i>,
+meaning salt; and <i>salarium</i>, or "salt-money," was
+money given for paying one's expenses on a journey.
+Living without salt would be a difficult matter.
+Cattle that have been shut away from it for a while
+are almost wild to get it. Farmers living among the
+mountains sometimes drive their cattle to a mountain
+pasture to remain there through the summer,
+and every little while they go up to salt the animals.
+The cattle know the call and know that it means
+salt; and I have seen them come rushing down the
+mountain-side and through the woods, over fallen
+trees, through briers, and down slippery rocks, bellowing
+as they came, and plunging head first in a
+wild frenzy to get to the pieces of rock salt that were
+waiting for them.</p>
+
+
+
+<hr style="width: 65%;" />
+<h2>FIRST YEAR IN NUMBER</h2>
+
+<p class="center">35 cents net. Postpaid</p>
+
+<p class="center">An Introductory Book to Precede any Series of
+Arithmetics</p>
+
+<p class="center">BY</p>
+
+<p class="center"><b>FRANKLIN S. HOYT</b></p>
+
+<p class="center"><i>Formerly Assistant Superintendent of Schools, Indianapolis</i></p>
+
+<p class="center">AND</p>
+
+<p class="center"><b>HARRIET E. PEET</b></p>
+
+<p class="center"><i>Instructor in Methods of Teaching Arithmetic, State Normal
+School, Salem, Massachusetts</i></p>
+
+<p>The work is based upon the familiar experiences and
+activities of children, and follows as closely as possible the
+child's own method of acquiring new knowledge and skill.</p>
+
+<p>Thus we have lessons based on playing store, making
+tickets, mailing letters, fishing, etc. Every step is made interesting,
+but no time is wasted in mere entertainment.</p>
+
+<hr style='width: 45%;' />
+
+<p class="center"><i>By the same authors</i></p>
+
+<h2>THE EVERYDAY ARITHMETICS</h2>
+
+
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" summary="books">
+<tr><td align='center'><b>THREE-BOOK COURSE</b></td></tr>
+<tr><td align='left'>Book One, grades II-IV.</td><td align='right'>$.40</td></tr>
+<tr><td align='left'>Book Two, grades V-VI</td><td align='right'>.40</td></tr>
+<tr><td align='left'>Book Three, grades VII-VIII</td><td align='right'>.45</td></tr>
+<tr><td align='center'><b>TWO-BOOK COURSE</b></td></tr>
+<tr><td align='left'>Book One, grades II-IV.</td><td align='right'>$.40</td></tr>
+<tr><td align='left'>Book Two, grades V-VIII.</td><td align='right'>.72</td></tr>
+<tr><td align='left'>Course of Study (with answers)</td><td align='right'> $.25</td></tr>
+</table></div>
+
+<p class="center"><i><b>Distinctive Features</b></i></p>
+
+<p>1. Their socialized point of view&mdash;all problems and topics
+taken from the everyday life of children, home interests,
+community interests, common business and industries.
+2. Their attractiveness to children&mdash;spirited illustrations,
+legible page, interesting subject matter. 3. The omission
+of all antiquated topics and problems. 4. The grouping of
+problems about a given life situation. 5. The development
+of accuracy and skill in essential processes. 6. The vocational
+studies. 7. The careful attention to method. 8. The
+exact grading. 9. The systematic reviews. 10. The adaptation
+to quick and to slow pupils.</p>
+
+<hr style='width: 25%;' />
+
+<p class="center">
+HOUGHTON MIFFLIN COMPANY<br />
+<small>BOSTON&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;NEW YORK&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;CHICAGO</small><br />
+<small>1901</small><br />
+</p>
+
+
+
+<hr style="width: 65%;" />
+<h3>"<i>A STEP FORWARD IN READING</i>"</h3>
+
+<h2><b>THE RIVERSIDE READERS</b></h2>
+
+<p class="center">EDITED BY</p>
+
+<h3>JAMES H. VAN SICKLE</h3>
+
+<p class="center"><i>Superintendent of Schools, Springfield, Mass.</i></p>
+
+<p class="center">AND</p>
+
+<h3>WILHELMINA SEEGMILLER</h3>
+
+<p class="center"><i>Late Director of Art, Indianapolis. Formerly Principal of the Wealthy
+Avenue Public School, Grand Rapids, Mich.</i></p>
+
+<p class="center">ASSISTED BY</p>
+
+<h3>FRANCES JENKINS</h3>
+
+<p class="center"><i>Instructor in Elementary Education, College for Teachers, University
+of Cincinnati, Formerly Supervisor of Elementary Grades, Decatur, Ill.</i></p>
+
+<p class="center">ILLUSTRATED BY</p>
+
+<p class="center"><b>
+RUTH MARY HALLOCK<br />
+MAGINEL WRIGHT ENRIGHT<br />
+CLARA E. ATWOOD<br />
+E. BOYD SMITH<br />
+HOWARD PYLE</b>, and other notable artists<br />
+</p>
+
+<p class="center">FRESH MATERIAL</p>
+
+<p>These Readers contain an unusually large amount of <i>fresh copyrighted
+material</i> taken from the world's best literature for children.</p>
+
+<p class="center">LATEST TEACHING METHODS</p>
+
+<p>They represent the latest developments in the methods of teaching reading,
+the kind of teaching that will be found in the best schools of to-day.</p>
+
+<p class="center">ARTISTIC MAKE-UP</p>
+
+<p>Artistically the books will set a new standard in text-book making.
+The colored Illustrations of the primary books are particularly
+attractive.</p>
+
+<p class="center">MECHANICAL FEATURES</p>
+
+<p>The paper used in the books, the type for each grade, and the dimensions
+and arrangement of the type page were all determined by careful
+experimenting, in order to safeguard the eyesight of children.</p>
+
+<p class="center"><i>Send for complete illustrated circular describing the unique plan
+of this series.</i></p>
+
+<p class="center"><b>PRICES</b></p>
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" summary="prices">
+<tr><td align='left'>Primer</td><td align='left'>30 cents, <i>net</i>.</td></tr>
+<tr><td align='left'>First Reader</td><td align='left'>35 cents, <i>net</i>.</td></tr>
+<tr><td align='left'>Second Reader</td><td align='left'>40 cents, <i>net</i>.</td></tr>
+<tr><td align='left'>Third Reader</td><td align='left'>50 cents, <i>net</i>.</td></tr>
+<tr><td align='left'>Fourth Reader</td><td align='left'>55 cents, <i>net</i>.</td></tr>
+<tr><td align='left'>Fifth Reader</td><td align='left'>55 cents, <i>net</i>.</td></tr>
+<tr><td align='left'>Sixth Reader</td><td align='left'>55 cents, <i>net</i>.</td></tr>
+<tr><td align='left'>Seventh Reader</td><td align='left'>55 cents, <i>net</i>.</td></tr>
+<tr><td align='left'>Eighth Reader,</td><td align='left'>60 cents, <i>net</i>.</td></tr>
+</table></div>
+
+<hr style='width: 25%;' />
+
+<p class="center">
+HOUGHTON MIFFLIN COMPANY<br />
+<small>BOSTON&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;NEW YORK&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;CHICAGO</small><br />
+<small>1901</small><br />
+</p>
+
+<hr style="width: 95%;" />
+<h3>Transcriber's Notes</h3>
+
+<p>The List of Illustrations was added, and some of the illustrations
+have been moved from their original positions to avoid breaking up
+paragraphs of text.</p>
+
+
+
+
+
+
+
+
+<pre>
+
+
+
+
+
+End of Project Gutenberg's Diggers in the Earth, by Eva March Tappan
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@@ -0,0 +1,3022 @@
+The Project Gutenberg EBook of Diggers in the Earth, by Eva March Tappan
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Diggers in the Earth
+
+Author: Eva March Tappan
+
+Release Date: March 6, 2008 [EBook #24762]
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK DIGGERS IN THE EARTH ***
+
+
+
+
+Produced by Diane Monico and The Online Distributed
+Proofreading Team at https://www.pgdp.net (This file was
+produced from images generously made available by The
+Internet Archive/American Libraries.)
+
+
+
+
+
+
+
+
+
+THE INDUSTRIAL READERS
+
+_Book II_
+
+DIGGERS IN THE
+EARTH
+
+BY
+
+EVA MARCH TAPPAN, Ph.D.
+
+_Author of "England's Story," "American Hero Stories,"
+"Old World Hero Stories," "Story of the Greek People,"
+"Story of the Roman People," etc. Editor of
+"The Children's Hour."_
+
+[Illustration]
+
+HOUGHTON MIFFLIN COMPANY
+
+BOSTON   NEW YORK   CHICAGO
+
+
+
+
+THE INDUSTRIAL READERS
+
+By Eva March Tappan
+
+  I. THE FARMER AND HIS FRIENDS. 50 cents.
+
+ II. DIGGERS IN THE EARTH. 50 cents.
+
+III. MAKERS OF MANY THINGS. 50 cents.
+
+ IV. TRAVELERS AND TRAVELING. 50 cents.
+
+The foregoing are list prices, postpaid
+
+
+COPYRIGHT, 1916, BY EVA MARCH TAPPAN
+ALL RIGHTS RESERVED
+
+_First printing April 1916;_
+_Reprinted December 1916_
+
+
+The Riverside Press
+CAMBRIDGE, MASSACHUSETTS
+U. S. A.
+
+
+
+
+PREFACE
+
+
+The four books of this series have been written not merely to provide
+agreeable reading matter for children, but to give them information.
+When a child can look at a steel pen not simply as an article
+furnished by the city for his use, but rather as the result of many
+interesting processes, he has made a distinct growth in intelligence.
+When he has begun to apprehend the fruitfulness of the earth, both
+above ground and below, and the best way in which its products may be
+utilized and carried to the places where they are needed, he has not
+only acquired a knowledge of many kinds of industrial life which may
+help him to choose his life-work wisely from among them; but he has
+learned the dependence of one person upon other persons, of one part
+of the world upon other parts, and the necessity of peaceful
+intercourse. Best of all, he has learned to see. Wordsworth's familiar
+lines say of a man whose eyes had not been opened,--
+
+    "A primrose by a river's brim
+    A yellow primrose was to him,
+    And it was nothing more."
+
+These books are planned to show the children that there is "something
+more"; to broaden their horizon; to reveal to them what invention has
+accomplished and what wide room for invention still remains; to teach
+them that reward comes to the man who improves his output beyond the
+task of the moment; and that success is waiting not for him who works
+because he must, but him who works because he may.
+
+Acknowledgment is due to the Lehigh Valley Railroad, Jones Brothers
+Company, Alpha Portland Cement Company, Dwight W. Woodbridge, the Utah
+Copper Company, the Aluminum Company of America, the Diamond Crystal
+Salt Company, T. W. Rickard, and others, whose advice and criticism
+have been of most valuable aid in the preparation of this volume.
+
+                                     EVA MARCH TAPPAN.
+
+
+
+
+CONTENTS
+
+   I. IN A COAL MINE                                   1
+
+  II. DOWN IN THE QUARRIES                            11
+
+ III. HOUSES OF SAND                                  21
+
+  IV. BRICKS, THEIR FAULTS AND THEIR VIRTUES          31
+
+   V. AT THE GOLD DIGGINGS                            39
+
+  VI. THE STORY OF A SILVER MINE                      48
+
+ VII. IRON, THE EVERYDAY METAL                        57
+
+VIII. OUR GOOD FRIEND COPPER                          65
+
+  IX. THE NEW METAL, ALUMINUM                         76
+
+   X. THE OIL IN OUR LAMPS                            84
+
+  XI. LITTLE GRAINS OF SALT                           95
+
+
+
+
+LIST OF ILLUSTRATIONS
+
+
+A STRUCTURAL STEEL APARTMENT BUILDING                 vi
+
+HOW A COAL MINE LOOKS ABOVEGROUND                      5
+
+MINERS AND THEIR MINE                                 10
+
+OPENING A GRANITE QUARRY                              13
+
+BUILDING A CONCRETE ROAD                              27
+
+IN A NEW JERSEY BRICK MILL                            33
+
+HYDRAULIC GOLD MINING                                 41
+
+THE STORY OF A SPOON                                  51
+
+IN THE STEEL FOUNDRY                                  61
+
+IN A COPPER SMELTER                                   67
+
+A "MOVIE" OF AN ALUMINUM FUNNEL                       79
+
+A CALIFORNIA OIL FIELD                                87
+
+
+
+
+[Illustration: A STRUCTURAL STEEL APARTMENT BUILDING
+
+_Courtesy American Bridge Co._
+
+First the steel frame, then the floors, then the stone or brick shell,
+then the interior finishing--this is how the building is made.]
+
+
+
+
+THE INDUSTRIAL READERS
+
+BOOK II
+
+DIGGERS IN THE EARTH
+
+
+
+
+I
+
+IN A COAL MINE
+
+
+Did you ever wonder how beds of coal happened to be in the earth? This
+is their story.
+
+Centuries ago, so many thousand centuries that even the most learned
+men can only guess at their number, strange things were coming to
+pass. The air was so moist and cloudy that the sun's rays had hard
+work to get through. It was warm, nevertheless, for the crust of the
+earth was not nearly so thick as it is now, and much heat came from
+the earth itself. Many plants and trees grow best in warm, moist air;
+and such plants flourished in those days. Some of their descendants
+are living now, but they are dwarfs, while their ancestors were
+giants. There is a little "horse-tail" growing in our meadows, and
+there are ferns and club mosses almost everywhere. These are some of
+the descendants; but many of their ancestors were forty or fifty feet
+high. They grew very fast, especially in swamps; and when they died,
+there was no lack of others to take their places. Dead leaves fell and
+heaped up around them. Stumps stood and decayed, just as they do in
+our forests to-day. Every year the soft, black, decaying mass grew
+deeper. As the crust of the earth was so thin, it bent and wrinkled
+easily. It often sank in one place and rose in another. When these
+low, swampy places sank, water rushed over them, pressing down upon
+them with a great weight and sweeping in sand and clay. Now, if you
+burn a heap of wood in the open air, the carbon in the wood burns and
+only a pile of ashes remains. "Burning" means that the carbon in the
+wood unites with the oxygen gas in the air. If you cover the wood
+before you light it, so that only a little oxygen reaches it, much of
+the carbon is left, in the form of charcoal.
+
+When wood decays, its carbon unites with the oxygen of the air; and so
+decay is really a sort of burning. In the forests of to-day the
+leaves, and at length the trees themselves, fall and decay in the open
+air; but at the time when our coal was forming, the water kept the air
+away, and much carbon was left. This is the way coal was made. Some of
+the layers, or strata, are fifty or sixty feet thick, and some are
+hardly thicker than paper. On top of each one is a stratum of
+sandstone or dark-gray shale. This was made by the sand and mud which
+were brought in by the water. These shaly rocks split easily into
+sheets and show beautiful fossil impressions of ferns. There are also
+impressions of the bark and fruit of trees, together with shells,
+crinoids, corals, remains of fishes and flying lizards, and some few
+trilobites,--crablike animals with a shell somewhat like the back of
+a lobster, but marked into three divisions or lobes, from which its
+name comes.
+
+Since the crust of the earth was so thin and yielding, it wrinkled up
+as the earth cooled, much as the skin of an apple wrinkles when the
+apple dries. This brought some of the strata of coal to the surface,
+and after a while people discovered that it would burn. If a vein of
+coal cropped out on a man's farm, he broke some of it up with his
+pickaxe, shoveled it into his wheelbarrow, and wheeled it home. After
+a while hundreds of thousands of people wanted coal; and now it had to
+be mined. In some places the coal stratum was horizontal and cropped
+out on the side of a hill, so that a level road could be dug straight
+into it. In other places the coal was so near the surface that it
+could be quarried under the open sky, just as granite is quarried.
+Generally, however, if you wish to visit a coal mine, you go to a
+shaft, a square, black well sometimes deeper than the height of three
+or four ordinary church steeples. You get into the "cage," a great
+steel box, and are lowered down, down, down. At last the cage stops
+and you are at the bottom of the mine. The miners' faces, hands,
+overalls, are all black with coal dust. They wear tiny lamps on their
+caps, and as they come near the walls of coal, it sparkles as it
+catches the light. Here and there hangs an electric lamp. It is doing
+its best to give out light, but its glass is thick with coal dust. The
+low roof is held up by stout wooden timbers and pillars of coal. A
+long passageway stretches off into a blacker darkness than you ever
+dreamed of. Suddenly there is a blaze of red light far down the
+passage, a roar, a medley of all sorts of noises,--the rattling of
+chains, the clattering of couplings, the shouts of men, the crash of
+coal falling into the bins. It is a locomotive dragging its line of
+cars loaded with coal. In a few minutes it rushes back with empty cars
+to have them refilled.
+
+All along this passageway are "rooms," that is, chambers which have
+been made by digging out the coal. Above them is a vast amount of
+earth and rock, sometimes hundreds of feet in thickness. There is
+always danger that the roof will cave in, and so the rooms are not
+made large, and great pillars of coal are left to hold up the roof.
+
+Not many years ago the miner used to do all the work with his muscles;
+now machines do most of it. The miner then had to lie down on his side
+near the wall of coal in his "room" and cut into it, close to the
+floor, as far as his pickaxe would reach. Then he bored a hole into
+the top of the coal, pushed in a cartridge, thrust in a slender squib,
+lighted it, and ran for his life. The cartridge exploded, and perhaps
+a ton or two of coal fell. The miner's helper shoveled this into a car
+and pushed it out of the room to join the long string of cars.
+
+[Illustration: HOW A COAL MINE LOOKS ABOVEGROUND
+
+All that shows on the surface is the machinery shed where the various
+engines work to keep the air fresh, and bring up the miners and the
+coal.]
+
+That is the way mining used to be done. In these days a man with a
+small machine for cutting coal comes first. He puts his cutter on the
+floor against the wall of coal and turns on the electricity. _Chip,
+chip_, grinds the machine, eating its way swiftly into the coal, and
+soon there is a deep cut all along the side of the room. The man and
+his machine go elsewhere, and the first room is left for its next
+visitors. They come in the evening and bore holes for the blasting.
+Once these holes were bored by hand, but now they are made with
+powerful drills that work by compressed air. A little later other men
+come and set off cartridges. In the morning when the dust has settled
+and the smoke has blown away, the loaders appear with their shovels
+and load the coal into the cars. Then it is raised to the surface and
+made ready for market.
+
+Did you ever notice that some pieces of coal are dull and smutty,
+while others are hard and bright? The dull coal is called bituminous,
+because it contains more bitumen or mineral pitch. This is often sold
+as "run-of-mine" coal,--that is, just as it comes from the mine,
+whether in big pieces or in little ones; but sometimes it is passed
+over screens, and in this process the dust and smaller bits drop out.
+
+The second kind of coal, the sort that is hard and bright, is
+anthracite. Its name is connected with a Greek word meaning ruby. It
+burns with a glow, but does not blaze. Most of the anthracite coal is
+used in houses, and householders will not buy it unless the pieces are
+of nearly the same size and free from dirt, coal dust, and slate. The
+work of preparation is done in odd-shaped buildings called "breakers."
+One part of a breaker is often a hundred or a hundred and fifty feet
+in height. The coal is carried to the top of the breaker. From there
+it makes a journey to the ground, but something happens to it every
+little way. It goes between rollers, which crush it; then over
+screens, through which the smaller pieces fall. Sometimes the screens
+are so made that the coal will pass over them, while the thin, flat
+pieces of slate will fall through. In spite of all this, bits of coal
+mixed with slate sometimes slide down with the coal, and these are
+picked out by boys. A better way of getting rid of them is now coming
+into use. This is to put the coal and slate into moving water. The
+slate is heavier than the coal, and sinks; and so the coal can easily
+be separated from it. Dealers have names for the various sizes of
+coal. "Egg" must be between two and two and five eighths inches in
+diameter; "nut" between three fourths and one and one eighth inches;
+"pea" between one half and three fourths of an inch.
+
+Mining coal is dangerous work. Any blow of the pickaxe may break into
+a vein of water which will burst out and flood the mine. The wooden
+props which support the roof may break, or the pillars of coal may not
+be large enough; and the roof may fall in and crush the workers. There
+are always poisonous gases. The coal, as has been said before, was
+made under water, and therefore the gas which was formed in the
+decaying leaves and wood could not escape. It is always bubbling out
+from the coal, and at any moment a pickaxe may break into a hole that
+is full of it. One kind of gas is called "choke-damp," because it
+chokes or suffocates any one who breathes it. There is also
+"white-damp," the gas which you see burning with a pretty blue flame
+over a hot coal fire. Worst of all is the "fire-damp." If you stir up
+the water in a marsh, you will see bubbles of it rise to the surface.
+It is harmless in a marsh, but quite the opposite in a mine. When it
+unites with a certain amount of air, it becomes explosive, and the
+least bit of flame will cause a terrible explosion. Even coal dust may
+explode if the air is full of it, and it is suddenly set in motion by
+too heavy a blast of powder.
+
+Miners used to work by candlelight. Every one knew how dangerous this
+was; but no one found any better way until, about a hundred years ago,
+Sir Humphry Davy noticed something which other people had not
+observed. He discovered that flame would not pass through fine wire
+gauze, and he made a safety lamp in which a little oil lamp was placed
+in a round funnel of wire gauze. The light, but not the flame, would
+pass through it; and all safety lamps that burn oil have been made on
+this principle. The electric lamp, however, is now in general use. The
+miner wears it on his cap, and between his shoulders he carries a
+small, light storage battery. Even with safety lamps, however, there
+are sometimes explosions. The only way to make a mine at all safe from
+dangerous gases is to keep it full of fresh, pure air. There is no
+wind to blow through the chambers and passages, and therefore air has
+to be forced in. One way is to keep a large fire at the bottom of the
+air shaft. If you stand on a stepladder, you will feel that the top of
+the room is much warmer than the floor. This is because hot air
+rises; and in a mine, the hot air over the fire rises and sucks the
+foul air and gas out of the mine, and fresh air rushes in to take its
+place. Another way is by a "fan," a machine that forces fresh air into
+the mine.
+
+[Illustration: MINERS AND THEIR MINE
+
+Notice the safety lamps in the men's caps, and the little railroad on
+which the cars of coal and ore travel, hauled by the useful mule.]
+
+So it is that by hard work and much danger we get coal for burning.
+Now, coal is dirty and heavy. A coal fire is hard to kindle and hard
+to put out, and the ashes are decidedly disagreeable to handle. And
+after all, we do not really burn the coal itself, but only the gas
+from it which results from the union of carbon and oxygen. In some
+places natural gas, as it is called, which comes directly from some
+storehouse in the ground, is used in stoves and furnaces and
+fireplaces for both heating and cooking; and perhaps before long gas
+will be manufactured so cheaply and can be used so safely and
+comfortably that we shall not have to burn coal at all, but can use
+gas for all purposes--unless electricity should take its place.
+
+
+
+
+II
+
+DOWN IN THE QUARRIES
+
+
+When walking in the country one day I came to a beautiful pond by the
+side of the road. The water was almost as clear as air, and as I
+looked down into it, I could see that the bottom was made of granite.
+The farther shores were cliffs of clean granite thirty or forty feet
+high and coming down to the water's edge. The marks of tools could be
+seen on them, showing where blocks of stone had evidently been split
+off. I picked up a piece of the rock and examined it closely. It
+proved to be made up of three kinds of material. First, there were
+tiny sparkling bits of mica. In some places there are mica mines
+yielding big sheets of this curious mineral which is used in the doors
+of stoves and the little windows of automobile curtains. With the
+point of a knife the bits in my piece of granite could be split into
+tiny sheets as thin as paper. The second material was quartz. This was
+grayish-white and looked somewhat like glass. The third material was
+feldspar. This, too, was whitish, but one or two sides of each bit
+were flat, as if they had not been broken, but split. This is the most
+common kind of granite. There are many varieties. Some of them are
+almost white, some dark gray, others pale pink, and yet others deep
+red. It is found in more than half the States of the Union.
+
+This quarry had been given up and allowed to fill with water; but it
+was a granite country, and farther down the road there was another,
+where scores of men were hard at work. This second quarry was part-way
+up a hill; or rather, it was a hill of granite which men were digging
+out and carrying away. When they began to open the quarry, much of the
+rock was covered with dirt and loose stones, and even the granite that
+showed aboveground was worn and broken and stained. This is called
+"trap rock." The easiest way to get rid of it is to blast with
+dynamite and then carry away the dirt and fragments. Next comes the
+getting out of great masses of rock to use, some of them perhaps long
+enough to make the pillars of a large building.
+
+[Illustration: OPENING A GRANITE QUARRY
+
+_Courtesy Jones Brothers Company._
+
+The first thing to do is to strip off the soil from the stone. Then,
+as the blocks are cut out, the big derrick lifts and loads them on
+waiting cars.]
+
+Now, granite is a hard stone, but there is no special difficulty in
+cutting it if you know how. In the old days, when people wished to
+split a big boulder, they sometimes built a fire beside it, and when
+it was well heated, they dropped a heavy iron ball upon it. King's
+Chapel in Boston was built of stone broken in this way. To break from
+a cliff, however, a block of granite big enough to make a long pillar
+is a different matter, and this is what the men were doing. First of
+all, the foreman had examined the quarry till he had found a stratum
+of the right thickness. He had marked where the ends were to come, and
+the men had drilled holes down to the bottom of the stratum. Then he
+had drawn a line at the back along where he wished the split to be,
+and the men had drilled on this line also a row of holes. Next came
+the blasting. If one very heavy charge had been exploded, it would
+probably have shattered the whole mass, or at any rate have injured it
+badly. Instead of this, they put into each hole a light charge of
+coarse powder and covered it with sand. These were all fired at the
+same instant, and thus the great block was loosened from the wall.
+Sometimes there seems to be no sign of strata, and then a line of
+horizontal holes must be drilled where the bottom of the block is to
+be. After this comes what is called the "plug-and-feather" process.
+Into each hole are placed two pieces of iron, shaped like a pencil
+split down the middle. These are the "feathers." The "plug" is a small
+steel wedge that is put between the iron pieces. Then two men with
+hammers go down the line and strike each wedge almost as gently as if
+it was a nut whose kernel they were afraid of crushing. They go down
+the line again, striking as softly as before. Then, if you look
+closely, you can see a tiny crack between the holes. There is more
+hammering, the crack stretches farther, a few of the wedges are driven
+deeper and the others drop out. The block splits off. A mighty chain
+is then wound about it, the steam derrick lifts it, lays it gently
+upon a car, and it is carried to the shed to be cut into shape,
+smoothed, and perhaps polished.
+
+In almost every kind of work new methods are invented after a while.
+In quarrying, however, the same old methods are in use. The only
+difference is that, instead of the work being done by muscle, it is
+done by compressed air or steam or electricity. Compressed air or
+steam works the drill and the sledgehammer. The drill is held by an
+arm, but the arm is a long steel rod which is only guided by the
+workman. Not the horse-sweep of old times, but the steam derrick and
+the electric hoist lift the heavy blocks from the quarry. Polishing
+used to be a very slow, expensive operation, because it was all done
+by the strength of some one's right arm, but now, although it takes as
+much work as ever, this work is done by machinery. To "point" a piece
+of stone, or give it a somewhat smooth surface, is done now with tools
+worked by compressed air. After this, the stone is rubbed--by
+machinery, of course--with water and emery, then by wet felt covered
+with pumice or polishing putty. A few years ago two young Vermonters
+invented a machine that would saw granite. This saw has no teeth, but
+only blades of iron. Between these blades and the piece of granite,
+however, shot of chilled steel are poured; and they do the real
+cutting.
+
+Granite has long been used in building wherever a strong, solid
+material was needed; but until the sand blast was tried, people
+thought it impossible to do fine work in this stone. There was a firm
+in Vermont, however, who believed in the sand blast. They had a
+contract with the Government to furnish several thousand headstones
+for national cemeteries. Cutting the names would be slow and costly;
+so they made letters and figures of iron, stuck them to the stones,
+and turned on the blast. If a sand blast is only fast enough, it will
+cut stone harder than itself. The blast was turned upon a stone for
+five minutes. Then the iron letters were removed. There stood in
+raised letters the name, company, regiment, and rank of the soldier,
+while a quarter of an inch of the rest of the stone, which the iron
+letters had not protected, had been cut away. By means of the sand
+blast it has become possible to do beautiful carving even in material
+as hard as granite.
+
+Granite looks so solid that people used to think it was fireproof; but
+it is really poor material in a great fire. Most substances expand
+when they are heated; but the three substances of which granite is
+made do not expand alike, and so they tend to break apart and the
+granite crumbles.
+
+A marble quarry is even more interesting than a granite quarry. If you
+stand on a hill in a part of the country where marble is worked, you
+will see white ledges cropping out here and there. The little villages
+are white because many of the houses are built of marble. Then, too,
+there are great marble quarries flashing in the sunshine. Sometimes a
+marble quarry is chiefly on the surface. Sometimes the marble
+stretches into the earth, and the cutting follows it until a great
+cavern is made, perhaps two or three hundred feet deep. A roof is
+often built to keep out the rain and snow. It keeps out the light,
+too, and on rainy days the roof, together with the smoke and steam of
+the engines, makes the bottom of the quarry a gloomy place. Everywhere
+there are slender ladders with men running up and down them. There
+are shouts of the men, clanking of chains, and puffing of locomotives.
+
+Marble is cut out in somewhat the same way as granite, but a valuable
+machine called a "channeler" is much used. This machine runs back and
+forth, cutting a channel two inches wide along the ends and back and
+sometimes the bottom of the block to be taken out.
+
+Marble is so much softer than granite that it is far more easy to
+work. Cutting it is a simple matter. The saw, which is a smooth flat
+blade of iron, swings back and forth, while between it and the marble
+sand and water are fed. It does not exactly _cut_, but rubs, its way
+through. The round holes in the tops of washstands are cut by saws
+like this, only bent in the form of a cylinder and turned round and
+round, going in a little deeper at each revolution. A queer sort of
+saw is coming into use. It is a cord made of three steel wires twisted
+loosely together. This cord is stretched tightly over pulleys and
+moves very rapidly. Every little ridge of the cord strikes the stone
+and cuts a little of it away.
+
+There are varieties of marble without end. The purest and daintiest is
+the white of which statues are carved; but there are black, red,
+yellow, gray, blue, green, pink, and orange in all shades. Many are
+beautifully marked. The inner walls of buildings are sometimes covered
+with thin slabs of marble. These are often carefully split, and the
+two pieces put up side by side, so that the pattern on one is reversed
+on the other. Certain kinds of marble contain fossils or remains of
+coral and other animals that lived hundreds of thousands of years ago.
+In some marbles there are so many that the stone seems to be almost
+made of them. When a slab is cut and polished, the fossils are of
+course cut into; but even then we can sometimes see their shape. One
+of the most common is the crinoid. This was really an animal, but it
+looked somewhat like a closed pond lily with a long stem, and people
+used to call it the stone lily. This stem is made up of little flat
+rings looking like bits of a pipestem. The stems are often broken up
+and these bits are scattered through the marble. The animals whose
+shells help to make marble lived in the ocean, and when they died sank
+to the bottom. Many of the shells were broken by the beating of the
+waves, but both broken shells and whole ones became united and
+hardened into limestone, one kind of which we call marble. Common
+chalk is another kind. Blackboard crayons are made of this: so are
+whitewash and whiting for cleaning silver and making putty.
+
+Another stone that builders would be sorry to do without is slate.
+This, too, was formed at the bottom of the sea. Rivers brought down
+fine particles of clay, which settled, were covered by other matter,
+and finally became stone. It was formed in layers, of course, but,
+queerly enough, it splits at right angles to its bottom line. Just why
+it does this is not quite certain, but the action is thought to be due
+to heat and long, slow pressure, which will do wonderful things, as in
+the case of coal. This splitting is a great convenience for the
+people who want to use it for roofing and for blackboards. Blocks of
+slate are loosened by blasting, and are taken to the splitting-shed.
+
+Splitting slate needs care, and a man who is not careful should never
+try to work in a slate quarry. The splitting begins by one man's
+dividing the block into pieces about two inches thick and somewhat
+larger than the slates are to be when finished. The way he does this
+is to cut a little notch in one end of the block with his "sculpin
+chisel" and make a groove from this across the block. He must then set
+his chisel into the groove, strike it with a mallet, and split the
+slate to the bottom. This sounds easy, but it needs skill. Slate has
+sometimes its own notions of behavior, and it does not always care to
+split in a straight line exactly perpendicular to the bottom of the
+stratum. The man keeps it wet so that he can see the crack more
+plainly, and if that crack turns back a little to the right, he must
+turn it to the left by striking the sculpin toward the left, or
+perhaps by striking a rather heavy blow on the left of the stone
+itself. Now the chief splitter takes it, and with a broad thin chisel
+he splits it into plates becoming thinner at each split. The second
+assistant trims these into the proper shape and size with either a
+heavy knife or a machine. Slate can be sawed and planed; but whatever
+is done to it should be done when it first comes from the quarry, for
+then it is not so likely to break. It would be very much cheaper if so
+much was not broken and wasted at the quarries and in the splitting.
+It is said that in Wales sometimes one hundred tons of stone are
+broken up to get between three and four tons of good slate. Within the
+last few years the quarrymen have been using channeling machines and
+getting out the slate in great masses instead of small blocks. This is
+not so wasteful by any means; but even now there is room for new and
+helpful inventions.
+
+
+
+
+III
+
+HOUSES OF SAND
+
+
+If you wanted to build a house, of what should you build it? In a new
+country, people generally use wood; but after a time wood grows
+expensive. Moreover, wood catches fire easily; therefore, as a country
+becomes more thickly settled and people live close together in cities,
+stone and brick are used. Large cities do not allow the building of
+wooden houses within a certain distance from the center, and sometimes
+even the use of wooden shingles is forbidden. Of late years large
+numbers of "concrete" or "cement" houses have been built. Our
+grandfathers would have opened their eyes wide at the suggestion of a
+house built of sand, and would have felt anxious at every rainfall
+lest their homes should suddenly melt away. Even after thousands of
+concrete buildings were in use, many people still feared that they
+would not stand the cold winters and hot summers of the United States;
+but it has been proved that concrete is a success provided it is
+properly made.
+
+No one can succeed in any work unless he understands how it should be
+done. Concrete is made of Portland cement, mixed with sand and water
+and either broken stone, gravel, cinders, or slag; but if any one
+thinks that he can mix these together without knowing how and produce
+good concrete, he will make a bad mistake rather than a good building
+material.
+
+First, he must buy Portland cement of the best quality. This cement is
+made of limestone and clay, or marl, chalk, and slag. These are
+crushed and ground and put into a kiln which is heated up to 2500 deg. or
+3000 deg.F.; that is, from twelve to fourteen times as hot as boiling
+water. The stone fuses sufficiently to form a sort of clinker. After
+this has cooled, it is ground so fine that the greater part of it will
+pass through a sieve having 40,000 meshes to the square inch. To every
+hundred pounds of this powder, about three pounds of gypsum is added.
+The mixture is then put into the bags in which we see it for sale in
+the stores. This powder is so greedy for water that it will absorb the
+moisture from the air around it. Even in the bags, it begins to harden
+as soon as it gets some moisture; and as soon as it hardens, it is of
+no use. The moral of that is to keep your cement in a dry place.
+
+The second substance needed in concrete is broken stone or gravel. Of
+course a hard rock must be selected, such as granite or trap rock.
+Limestone calcines in a heat exceeding 1000 deg. F., and therefore it
+cannot be used in fireproof construction. Soft rock, like slate or
+shale or soft sandstone, will not answer because it is not strong
+enough. Gravel is always hard. If you look at a cut in a gravel bank,
+you will usually see strata of sand and then strata of rounded pebbles
+of different sizes. The sand was once an ancient sea beach; the
+pebbles were dashed up on it by waves or storms or some change of
+currents. They were at first only broken bits of rock, but after being
+rolled about for a few thousand years in the ocean and on the shore,
+the corners were all rounded. Soft rock would have been ground to
+powder by such treatment. Sometimes, if there is to be no great strain
+on the concrete, cinders or pieces of brick may be used instead of
+stone; and for some purposes they answer very well.
+
+The third substance used in concrete is sand; but it must be the right
+kind of sand, having both fine and coarse grains. These grains need to
+be sharp, or the cement will not stick to them well. They must also be
+clean, that is, free from dirt. If you rub sand between your hands,
+and it soils them, then there is clay or loam with it, and it must not
+be used in making concrete unless it is thoroughly washed. Another way
+of testing it is to put it into a glass jar partly full of water and
+shake it. Then let it settle. If there is soil in the sand, it will
+appear as a stratum of mud on top of the sand.
+
+The water with which these three substances are to be mixed must be
+clean and must contain no acid and no strong alkali. As a general
+rule, there must be twice as much broken stone as sand. When people
+first make concrete, they often expect too much of their materials. A
+good rule for the strongest sort of cement, strong enough for floors
+on which heavy machines are to stand, is one fourth of a barrel of
+cement, half a barrel of sand, and one barrel of gravel or broken
+stone. Apparently this would make one and three fourths barrels; but
+in reality it makes only about one barrel, because the sand fills in
+the spaces between the gravel, and the cement fills in the spaces
+between the grains of sand.
+
+There are many sorts of machines on the market for mixing the
+materials; but small quantities can just as well be mixed by hand. The
+"mixing-bowl" is a platform, and on this the sand is laid. Then comes
+the cement; and these two must be shoveled together several times.
+While this is being done, the broken stone or gravel must be wet, and
+now it is put on top of the sand and cement and well shoveled
+together, with just enough water added so that the mass will almost
+bear the weight of a man.
+
+Concrete is impatient to be hardening, and if it is not put into the
+right place, it will begin promptly to harden in the wrong place, and
+nothing can be done with it afterwards. If it is to be made in blocks,
+the moulds must be ready and the concrete put into them at once and
+well tamped down. For such uses as beams and the sides of tanks where
+great strength is needed, the cement is often "reinforced," that is,
+rods of iron or steel are embedded in it. For floors, a sheet of woven
+wire is often stretched out and embedded. At first only solid blocks,
+made to imitate rough stone, were used for houses, but the hollow
+block soon took their place. This is cheaper; houses built this way
+are warmer in winter and cooler in summer; and it prevents moisture
+from working through the walls. Many cities have regulations about the
+use of hollow blocks, all the more strict because concrete is
+comparatively new as a building material. In Philadelphia the blocks
+must be composed of at least one barrel of Portland cement to five
+barrels of crushed rock or gravel. They must be three weeks old or
+more before being used; the lintels and sills of the doors must be
+reinforced; and every block must be marked, so that if the building
+should not prove to be of proper strength, the maker may be known.
+There would seem, however, to be little question of the quality of the
+blocks, for samples must pass the tests of the Bureau of Building
+Inspection.
+
+Even better than the hollow block is the method of making the four
+walls of a house at once by building double walls of boards and
+pouring in the concrete. When this has hardened, the boards are
+removed, and whatever sort of finish the owner prefers is given to the
+walls. They can be treated by spatter-work, pebble dash, or in other
+ways before the cement is fully set, or by bush hammering and tool
+work after the cement has hardened. Coloring matter can be mixed with
+the cement in the first place; and if the owner decides to change the
+color after the house is completed, he can paint it with a thin cement
+of coloring matter mixed with plaster of Paris.
+
+A concrete house has several advantages. In the first place, it will
+not burn. Neither will granite, but granite will fall to pieces in a
+hot fire. Granite is made of quartz, mica, and feldspar, as has been
+said before. These three do not expand alike in heat; and therefore
+great flakes of the stone split off, so that it really seems to melt
+away. A well-made concrete is not affected by fire. It will not burn,
+and it will not carry heat to make other things burn. For a concrete
+house no paint is needed and less fuel will be required to keep it
+warm. If the floors are made with even a very little slant,
+"house-cleaning" consists of removing the furniture and turning on the
+hose. Water-tank, sink, washtubs, and bathtubs can be cast in concrete
+and given a smooth finish. Wooden floors can be laid over the
+concrete, or a border of wood can be put around each room for tacking
+down carpets or rugs. A concrete house may be as ornamental as the
+owner chooses, for columns and cornices and mouldings can easily be
+made of concrete; and if they are cast in sand, as iron is, they will
+have a finish like sandstone.
+
+It is somewhat troublesome to lay concrete in very cold weather,
+because of the danger of freezing and cracking. Sometimes the
+materials are heated, and after the concrete is in place, straw or
+sand or sawdust is spread over it. These will keep it warm for several
+hours, and so give the concrete a chance to "set." Sometimes a canvas
+house is built over the work. When a concrete dam was to be built in
+the Province of Quebec and the mercury was 20 deg. below zero, the
+contractors built a canvas house over one portion of the dam and set
+up iron stoves in it. When this part was completed, they took down the
+house and built it up again over another portion of the dam.
+Sometimes salt is used. Salt water is heavier than fresh water and
+will not freeze so easily. Therefore salt put into the water used in
+making the concrete will enable it to endure more cold without
+freezing; but not more than one pound of salt to twelve gallons of
+water should be used.
+
+[Illustration: BUILDING A CONCRETE ROAD
+
+_Courtesy Alpha Portland Cement Co._
+
+The concrete mixer travels along the prepared roadbed, and after it
+follow the workmen with levelers and stamps.]
+
+Concrete objects to being frozen before it is "set," but it is
+exceedingly accommodating about working under water. It must, of
+course, be carried in some way through the water to its proper place
+without being washed away, but this is easily done. Sometimes it is
+let down in great buckets closed at the top, but with a hinged bottom
+that will open when the bucket strikes the rock or soil where the
+material is to be left. Sometimes it is poured down through a tube.
+Sometimes it is dropped in sacks made of cloth. This cloth must be
+coarse, so that enough of the concrete will ooze through it to unite
+the bag and its contents with what is below it and make a solid mass.
+Sometimes even paper bags have been successfully used. The concrete,
+made rather dry, is poured into the bags and they are slid down a
+chute. The paper soon becomes soft and breaks, and lets the concrete
+out. Sometimes concrete blocks are moulded on land and lowered by a
+derrick, while a diver stands ready to see that they go into their
+proper places.
+
+Concrete is used for houses, churches, factories, walls, sidewalks,
+steps, foundations, sewers, chimneys, piers, cellar bottoms, cisterns,
+tunnels, and even bridges. In the country, it is used for silos, barn
+floors, ice houses, bins for vegetables, box stalls for horses,
+doghouses, henhouses, fence posts, and drinking-troughs. It is of very
+great value in filling cavities in decaying trees. All the decayed
+wood must be cut out, and some long nails driven from within the
+cavity part-way toward the outside, so as to help hold the concrete.
+Then it is poured in and allowed to harden. If the cavity is so large
+that there is danger of the trunk's breaking, an iron pipe may be set
+in to strengthen it. If this is encased in concrete, it will not rust.
+A horizontal limb with a large cavity may be strengthened by bending a
+piece of piping and running one part of it into the limb and the other
+into the trunk, then filling the whole cavity with concrete. If the
+bark is trimmed in such a way as to slant in toward the cavity, it
+will sometimes grow entirely over it.
+
+Concrete is also used for stucco work, that is, for plastering the
+outside of buildings. If the building to be stuccoed is of brick or
+stone, the only preparation needed is to clean it and wet it; then put
+on the plaster between one and two inches thick. A wooden house must
+first be covered with two thicknesses of roofing-paper, then by wire
+lathing. The concrete will squeeze through the lathing and set. Stucco
+work is nothing new, and if it is well done, it is lasting.
+
+Concrete has been used for many purposes besides building, and the
+number of purposes increases rapidly. For blackboards, refrigerator
+linings, and railroad ties it has been found available, and for poles
+or posts of all sizes it has already proved itself a success. It has
+even been suggested as an excellent material for boats, if reinforced;
+and minute directions are given by one writer for making a concrete
+rowboat. To do this, the wooden boat to be copied is hung up just
+above the ground, and clay built around it, leaving a space between
+boat and clay as thick as the concrete boat is to be. The wooden boat
+is covered with paper and greased, then the concrete is poured into
+the space between the boat and the clay mould; and when it hardens and
+the wooden boat is removed, there is a boat of stone--or so the
+directions declare; but I think most people would prefer one of wood.
+However it may be with rowboats, concrete is taking an important place
+in the construction of battleships, a backing for armor being made of
+it instead of teakwood. The Arizona is built in this way.
+
+Concrete that is carelessly made is very poor stuff, and dangerous to
+use, for it is not at all reliable and may give out at any time; but
+concrete that is made of the best materials and properly put together
+is an exceedingly valuable article.
+
+
+
+
+IV
+
+BRICKS, THEIR FAULTS AND THEIR VIRTUES
+
+
+The simplest way to make a brick is to fill a mould with soft clay,
+then take it out and let it stiffen, and then put it in the sun to
+dry. This is the way in which the "adobe" bricks of Central America
+are made. They answer very well in countries where there is little
+rain; but one or two heavy downpours would be likely to melt a house
+built of such material.
+
+Clay is a kind of earth containing mostly alumina and silica or sand,
+that can be mixed with water, moulded into any shape, retain that
+shape after it is dry, and become hard by being burned. If you want to
+make a china cup, you must have a fine sort of clay called "kaolin,"
+which is pure white when it is fired and is not very common; but if
+you want to make bricks, it will not be at all difficult to find a
+suitable clay bank. And yet the clay, even for bricks, must be of the
+right kind. If it contains too much silica (sand), the brick will not
+mould well; if too much alumina it will be weak; if too much iron, it
+will lose its shape in burning; if too much lime, it will be
+flesh-colored when it is burned.
+
+If you want to find out whether a building-brick is of good quality,
+there are some tests that a boy or girl can apply as well as any one.
+First, look the brick over and note whether it is straight and true,
+and whether the edges and corners are sharp. Strike it, and see
+whether it gives a clear, ringing sound. Then weigh it and soak it in
+water for twenty-four hours. Weigh it again, and if it is more than
+one fifth heavier than it was before soaking, it is not of the first
+quality.
+
+After the clay has been dug, it must be "tempered," that is, mixed
+with water and about one third or one fourth as much sand as clay, and
+left overnight in a "soak pit," a square pit about five feet deep. In
+the morning the workmen shovel the mass over and feed it into the
+machines for forming the bricks. The mixing is better done, however,
+in a "ring pit." This is a circular pit twenty-five or thirty feet in
+diameter, three feet deep, and lined with boards or brick. A big iron
+wheel works from the center to the edge and back again for several
+hours, through and through the clay. A method even better than this is
+to put the clay and sand and water into a great trough, in which there
+is a long shaft bristling with knives. The shaft revolves, mixes the
+clay, and pushes it along to the end of the trough. This is called
+"pugging," and the whole thing--trough, shaft, and knives--is a "pug
+mill."
+
+In the old days bricks were always made by hand. The moulder stood in
+front of a wet table whereon lay a heap of soft clay. He either wet or
+sanded his mould to keep it from sticking. Meanwhile, his assistant
+had cut a piece of clay and rolled it and patted it into the shape of
+the mould. In making bricks, there can be no patching; the mould
+must be filled at one stroke, or else there will be folds in the
+brick. To make a good brick, the moulder lifts the clay up above his
+head and throws it into the mould with all his force. Then he presses
+it into the corners with his thumbs, scrapes off with a strip of wood
+any extra clay, or cuts it off with a wire, smooths the surface of the
+brick, puts mould and brick upon a board, jerks the mould up and
+proceeds to make another brick.
+
+[Illustration: IN A NEW JERSEY BRICK MILL
+
+_Copyright by Underwood and Underwood._
+
+This man is moulding a fire-brick to its final shape.]
+
+No matter how expert a moulder may be, brick-making by hand is slow
+work, and in most places machines are used. In what is called the
+"soft-mud" process, the clay is pushed on by the pug mill to the end
+of the trough. There stands a mould for six bricks. A plunger forces
+the clay into it, the mould is emptied, and in a single hour five
+thousand bricks can be made. By what is called the "stiff-mud"
+process, the stiff clay is put into a machine with an opening the size
+of the end or side of a brick. The machine forces the clay through
+this opening, cuts it off at the proper moment; and so makes bricks by
+the thousand without either mould or moulder. A third way of making
+brick is by what is called the "dry process." The clay is pulverized
+and filled into moulds the length and breadth of a brick, but much
+deeper, and with neither top nor bottom. One plunger from above and
+another from below strike the clay in the mould with much force, and
+make the fine, smooth brick known as "pressed brick." All this is done
+by machinery, and some machines make six bricks at a time. These
+"dry" bricks are fragile before they are burned, and must be handled
+with great care.
+
+Bricks cannot be put into the kiln while they are still wet, for when
+a brick is drying, it is a delicate article. It objects to being too
+hot or too cold, and it will not stand showers or drafts. In some way
+about a pound of water must be dried out of each brick; but if you try
+to hurry the drying, the brick turns sulky, refuses to have anything
+more to do with you, and proceeds to crack. To dry, bricks are
+sometimes spread on floors; or piled up in racks on short pieces of
+board called "pallets"; and sometimes they are put upon little cars
+and run slowly through heated tunnels. The last is the best way for
+people who are in a hurry, for it takes only from twenty-four to
+thirty-six hours to make the bricks ready to go to the kiln to be
+burned.
+
+In one sort of kiln, the bricks themselves make the kiln. They are
+piled up in arches, but left a little way apart so the hot air can
+move freely among them. The sides of the structure are covered with
+burnt brick and mud, but the top is left open to allow the steam from
+the hot bricks to escape. The fires are in flues that are left at the
+bottom. They must burn slowly at first, but after a while, some forty
+to sixty hours, the heat becomes intense. Thus far the bricks have
+been grayish or cream-colored, but now, if there is iron in them, they
+turn red; if there is lime, they turn yellow; if a large amount of
+lime, they become flesh-colored. Besides this sort of kiln, which is
+torn down when the bricks are sufficiently burned, there is also the
+permanent kiln, which has fixed side walls and either an open or
+closed top. Then, too, there is a "continuous" kiln. This has a number
+of chambers, and the heat from each one passes into the next; so that
+bricks in one chamber may be just warming up while in another they are
+ready to be taken out.
+
+When the bricks come out of the kiln, some of them are good and some
+are not. Those that were on the outside are not burned enough; those
+next it are not well baked, but can be used for the middle of thick
+walls. The next ones are of good quality; but those directly over the
+fires are so hard and brittle that they are of little use except for
+pavements.
+
+Paving-bricks, however, are not to be despised. They are not as smooth
+and well finished as pressed brick, but they are exceedingly useful.
+They need as much care in making as any others, and they must be
+burned in a much hotter fire to make them dense and hard. The tests
+for paving-bricks are quite different from those for ordinary
+building-brick. If first-class paving-bricks weighing fifty pounds are
+soaked in water for twenty hours, they take up so little water that
+they will not weigh more than fifty-one or fifty-one and a half pounds
+when taken out. To find out how hard they are, the bricks are weighed
+and shaken about with foundry shot for a number of hours. Then they
+are weighed again to see how much of their material has been rubbed
+off. A third test is to put one brick on edge into a crushing machine
+to see how much pressure it will stand. Paving-brick is cheaper than
+granite blocks, and if it has a good foundation of concrete covered
+with sand, it will last about three fourths as long. Brick is less
+noisy than stone and is easier to clean.
+
+Not so very long ago, when particularly handsome bricks were needed
+for the outside of walls and other places where they would be
+conspicuous, they were "re-pressed"; that is, they were made by hand
+or in a "soft-mud" machine, and then, after drying for a while, were
+put into a re-pressing machine to give them a smooth finish. These
+machines are still used, but they are hardly necessary, for the
+"dry-clay" brick machine will turn out a smooth brick in one
+operation.
+
+Another substance which is made of almost the same materials as brick
+is terra cotta. To make this, fire brick, bits of pottery, partly
+burned clay, and fine white sand are ground to a powder and mixed very
+thoroughly. This mixture is moulded, dried, and burned. Until
+recently, all terra cotta was of the color that is called by that
+name, but now it is made in gray, white, and bronze as well.
+
+Bricks are laid in mortar, and this makes a wall one solid mass and
+stronger than it could be without any cement. But mortar does more
+than this. It is more elastic than brick, and therefore, when a wall
+settles, the mortar yields a little, and this often prevents the
+bricks from cracking. Bricks are always thirsty, and if one is laid in
+mortar, it will suck the moisture out of it almost as a sponge will
+suck up water. The mortar thus has no chance to set, and so is not
+strong as it should be. That is why the bricklayer wets his bricks,
+especially in summer, before he puts them in place. Lime or cement
+mortar will not set in freezing weather, and a brick building put up
+in the winter is in danger of tumbling down when the warm days of
+spring arrive.
+
+This thirstiness of bricks is their greatest fault. Three or four days
+of driving rain will sometimes wet through a brick wall two feet
+thick, crumbling the plaster and spoiling the wallpaper. That is why
+it is a poor plan to plaster directly on the brick wall of a house.
+"Furring" strips, as they are called, or narrow strips of wood, should
+be fastened on first and the laths nailed to these, or the wall can be
+painted or oiled on the outside. The best way, however, though more
+expensive, is to build the wall double. Then there is air between the
+two thicknesses of brick. Air is a poor conductor of heat; so in
+summer it keeps the heat out, and in winter it keeps it in.
+
+But brick will suck up water from the ground as well as from a storm;
+and therefore, when a brick house is to be built in a wet place, there
+ought to be a three-eighths-inch layer of something waterproof, like
+asphalt and coal tar, put on top of one of the layers of brickwork to
+prevent the moisture from creeping up.
+
+Bricks have their faults, but they will not burn, and when properly
+used, they make a most comfortable and enduring house.
+
+
+
+
+V
+
+AT THE GOLD DIGGINGS
+
+
+When gold was first discovered in California, in 1848, people from all
+over the world made a frantic rush to get there, every one of them
+hoping that he would be lucky enough to make his fortune, and fearing
+lest the precious metal should be gone before he could even begin to
+dig. The gold that these men gathered came from what were called
+"placers"; that is, masses of gravel and sand along the beds of
+mountain streams. Each miner had a pan of tin or iron, which he filled
+half-full of the gravel, or "pay dirt," as the miners called it. Then,
+holding it under water, he shook off the stones and mud over the side
+of the pan, leaving grains of gold mixed with black sand at the
+bottom. This black sand was iron, and after a while the miners removed
+it with a magnet, dried what remained, and blew away the dust, leaving
+only the grains of gold.
+
+Another contrivance which soon came into use was the "cradle." This
+was a long box, sometimes only a hollowed-out log. At the top was a
+sieve which sifted out the stones. Nailed to the bottom of the cradle
+were small cleats of wood, or "riffles," which kept the water from
+running so fast as to sweep the gold out of the cradle with it. The
+cradle was placed on rockers and was also tilted slightly. The miner
+shoveled the gravel into the top of the cradle and his partner rocked
+it. The sieve kept back the stones, the water broke up the lumps of
+earth and gravel and washed them down the cradle, and the grains of
+gold were stopped by the riffles, and sank to the bottom. Sometimes
+the "pay dirt" continued under a stream. To get at it, the miners
+often built a little canal and turned the water into a new channel;
+then they could work on the former bed of the river.
+
+Before many years had passed, the gold that was near the surface had
+been gathered. The miners then followed the streams up into the
+mountains, and found that much of the gold had come from beds where in
+ancient times rivers had flowed. There was gold still remaining in
+these beds, but it was poorly distributed, the miners thought.
+Sometimes there would be quite an amount in one place, and then the
+miner would dig for days without finding any more. Even worse than
+this was the fact that these gravel beds were not on the top of the
+ground, but were covered up with soil and trees. Evidently the slow
+work with pans and cradles would not pay here; but it occurred to some
+one that if a powerful stream of water could be directed against the
+great banks of earth, as water is directed against a burning building,
+they would crumble, the dirt could be washed down sluices, and the
+gold be saved. This was done. Great reservoirs were built high up in
+the mountains, and water was brought by means of ditches or pipes to a
+convenient place. Then it was allowed to rush furiously through a
+hose and nozzle, and the great stream coming with tremendous force was
+played upon the banks of gravel. The banks crumbled, the gravel was
+washed into a string of sluices, or long boxes with riffles to catch
+the gold. Soon the miners found that if quicksilver was put into these
+sluices, it would unite with the gold and make a sort of paste called
+"amalgam." Then if this amalgam was heated, the quicksilver would be
+driven off in the form of gas, and the gold would remain in a
+beautiful yellow mass.
+
+[Illustration: HYDRAULIC GOLD MINING
+
+A placer mine at Gold Point, California, where tremendous streams of
+water under high pressure are busy washing away the side of a
+gold-bearing hill.]
+
+The ancient rivers had also carried gold to the valleys, and to
+collect this a dredge, which the miners called a "gold ship," came
+into use. The "ship" part of this machine is an immense flat scow.
+Stretching out from one end is something which looks like a moving
+ladder. This is the support of an endless chain of buckets, each of
+which can bite into the gravel and take a mouthful of five or six
+hundred pounds. They drop this gravel into a big drum which is
+continually revolving. Water flows through the drum, and washes out
+the sand and bits of gold over large tables, where by means of riffles
+and quicksilver the gold is captured. This scow was usually on dry
+land at first; but its digging soon made a lake, and then it floated.
+It must be more fascinating to hold a pan in your own hands and pick
+out little grains of gold or perhaps even a big piece of it with your
+own fingers, but if the gravel is good the dredge makes more money.
+
+In Alaska the great difficulty in mining is that, except at the
+surface, the ground is frozen all the year round. At first, the miners
+used to thaw the place where they wished to dig by building wood
+fires; but this was a slow method, and now the thawing is done by
+steam. They carry the steam in a pipe to the place where the digging
+is to be done, and send it through a hose. At the end of the hose is a
+pointed steel tube. They hammer this tube into the ground and let some
+steam pass through the nozzle. This softens the ground so that picks
+and shovels may be used. There is generally cold enough in Alaska, but
+once at least the miners had to manufacture it. The gold-bearing
+gravel was deep, the ground was flat, and it was often overflowed.
+They set up a freezing plant, and shut in their land with a bulkhead
+of ice several feet thick. Then they pumped out what water was already
+in and did their work with no more trouble.
+
+When gold began to grow less in the California gravel, the miners
+looked for it in the rocks on the mountain-side. The placer miners
+laughed at them and called their shafts "coyote holes"; but in time
+the placers failed, while nearly all of our gold to-day comes from
+veins of white quartz in the rocks. A vein of gold is the most
+capricious thing in the world. It may be so tiny that it can hardly be
+seen, then widen and grow rich in gold, then suddenly come to an end.
+This is why a new mine is so uncertain an enterprise. The gold may
+hold out and bring fortunes to the investors, or it may fail, and then
+all they will have to show for their money is the memory that they
+put it into a hole in the ground. The managers of a few of the
+well-established mines, however, have explored so far as to make sure
+that there is gold enough for many years of digging.
+
+The mining engineer must be a very wide-awake man. It is not enough
+for him simply to remember what was taught him in the schools of
+mining; he must be bright enough to invent new ways of meeting
+difficulties. No two mines are alike, and he must be ready for all
+sorts of emergencies. A gold mine now consists of a shaft or pit dug
+several hundred feet down into the rock, with levels or galleries
+running off from it and with big openings like rooms made where the
+rock was dug out. The roofs of the rooms are supported by great
+timbers. To break away the rock, the miner makes a hole with a rock
+drill worked by electricity or compressed air, puts powder or dynamite
+into the hole and explodes it. The broken rock is then raised to the
+surface and crushed in a "stamping mill." Here the ore is fed into a
+great steel box called a "mortar." Five immense hammers, often
+weighing a thousand pounds apiece, drop down upon the ore, one after
+another, until it is fine enough to go through a wire screen in the
+front of the box. When two hundred or more of these hammers are
+pounding away with all their might, a stamping mill is a pretty noisy
+place. The ore, crushed to a fine mud, now runs over sloping tables
+covered with copper. Sticking to the top of the copper is a film of
+quicksilver. This holds fast whatever gold there may be and makes an
+amalgam, which is scraped off from time to time, and the quicksilver
+is driven from the gold by heat.
+
+Gold that is not united with other metals is called "free milling
+gold." Much of it, however, is found in combination with one metal or
+another, and is known as "rebellious" or "refractory" gold. Such gold
+may sometimes be set free by heat, and sometimes by chemicals. One way
+is by the use of chlorine gas, and the story of it sounds almost like
+"The house that Jack built." It might run somewhat like this: This is
+the salt that furnishes the chlorine. This is the chlorine gas that
+unites with the gold. This is the chloride that is formed when the
+chlorine gas unites with the gold. This is the water that washes from
+the tank the chloride that is formed when the chlorine gas unites with
+the gold. This is the sulphate of iron that unites with the chlorine
+gas of the chloride that the water washes from the tank that is formed
+when the chlorine gas unites with the gold--and leaves the gold free.
+
+Another method is by the use of cyanide. More than a century ago a
+chemist discovered that if gold was put into water containing a little
+cyanide, the gold would dissolve, while quartz and any metals that
+might be united with the gold would settle in the tank. The water in
+which the gold is dissolved is now run into boxes full of shavings of
+zinc and is "precipitated" upon them; that is, the tiny particles of
+gold in the water fall upon the zinc and cling to it. Zinc melts more
+easily than gold, so if this gilded zinc is put into a furnace, the
+zinc melts and the gold is set free.
+
+Very often gold is found combined with lead or copper. It must then be
+melted or smelted in great furnaces. The metal is heavier than the
+rock and settles to the bottom of the furnace. It is then drawn off
+and the gold is separated from the other metals, usually by
+electricity.
+
+Sometimes large pieces of gold called "nuggets" are found by miners.
+The largest one known was found in Australia. It weighed 190 pounds
+and was worth $42,000. Sometimes spongy lumps of gold are found; but
+as a general thing gold comes from the little specks scattered through
+veins in rock, and much work has to be done before it can be made into
+coins or jewelry. It is too soft for such uses unless some alloy,
+usually copper or silver, is mixed with it to make it harder.
+Sometimes it is desirable to know how much alloy has been added. The
+jeweler then makes a line with the article on a peculiar kind of black
+stone called a "touchstone," and by the color of the golden mark he
+can tell fairly well how nearly pure the article is. To be more
+accurate, he pours nitric acid upon the mark. This eats away the alloy
+and leaves only the gold.
+
+Gold is a wonderful metal. It is of beautiful color; it can be
+hammered so thin that the light will shine through it; few acids
+affect it, and the oxygen which eats away iron does not harm it. Pure
+gold is spoken of as being "twenty-four carats fine," from _carat_, an
+old weight equal to one twenty-fourth of an ounce troy. Watchcases
+are from eight to eighteen carats fine; chains are seldom more than
+fourteen; and the gold coins of the United States are about eleven
+parts of gold and one of copper. Coins wear in passing from one person
+to another, and that is why the edges are milled, so that it may be
+more easily seen when they have become too light to be used as coins.
+When such pieces come into the hands of the Government, they must be
+recoined.
+
+
+
+
+VI
+
+THE STORY OF A SILVER MINE
+
+
+A man who goes out in search of a mine is called a "prospector." The
+best prospector is a man who has learned to keep his eyes open and to
+recognize the signs of gold and silver and other metals. A faithful
+friend goes with him, a donkey or mule which carries his bacon and
+beans, blankets, saucepan, and a few tools, such as a pan, pick,
+shovel, hammer, and axe. Sometimes the prospector also takes with him
+a magnifying glass and a little acid to test specimens, but usually he
+trusts to his eyes alone.
+
+When these few things have been brought together, the prospector and
+the donkey set out. They wander over the hills and down into the
+canyons. If a rock is stained red, the prospector examines it to see
+whether it contains iron; if it is green, he looks for copper. In the
+canyons and along the creeks he often tests the gravel for traces of
+some valuable metal. If he finds any of these traces along the stream,
+he follows them on the bank until they stop; then he carefully
+examines the bank of the stream or the nearest hillside. If he
+continues to find bits of metal, they will lead him to a vein of ore,
+from which they have been broken by the wind, rain, and frost.
+
+Generally a prospector is looking for some one special metal, and in
+his search he often overlooks some other metal; for instance,
+thousands of the gold-seekers who rushed to California in 1849 hurried
+through Nevada on their way. If they had only known what was under
+their feet, they would have taken their picks and shovels and begun to
+dig, instead of trying to get out of the region as soon as might be.
+Ten years later, the California placers were becoming exhausted, and
+miners began to go elsewhere in their search for gold.
+
+Among those who were working in what is now the State of Nevada were
+two Irishmen who had been unlucky in California and had fared no
+better in Nevada. They wanted to go somewhere else, but they had not
+money enough for the journey; so they kept on with their work at the
+foot of Mount Davidson, washing the gravel and saving the little gold
+that they found. They were annoyed by some heavy black stuff that
+united with the quicksilver in their cradles, interfered with the
+saving of the gold, and put them in a very bad temper. At length a man
+named Henry Comstock came along, who told them that this black stuff
+was silver ore. They examined the mountain-side, and discovered the
+outcrop or edge of a great vein containing gold and also silver. It is
+no wonder that people rushed from the east and west to the wonderful
+new mines, for it was plain that these new "diggings" were not mere
+placers, but rich veins that many years of working might not exhaust.
+Every newcomer hoped to discover a vein; and within a year or two the
+district around the Comstock lode was full of deep shafts, many of
+them abandoned and half-hidden by low brush, but some of them yielding
+quantities of gold and silver. Before this, there had been only about
+a thousand people in what is now Nevada, but in two years after the
+discovery of silver, there were 16,000, and a new Territory was
+formed.
+
+The miners knew how to get gold out of ore, but silver was another
+matter, and some of it was difficult to extract. They had so much
+trouble that they were ready to believe in any treatment of the ore,
+no matter how absurd, that promised to help them out of their
+difficulties. Some of them were actually persuaded that the juice of
+the wild sagebrush would bring the silver out. It is no wonder that
+they were troubled, for in the Comstock lode were not only gold and
+silver, but ten or twelve other metals or combinations of silver with
+something else. At length processes were invented for treating the
+different kinds of ore. Some kinds were crushed in a stamping mill,
+then ground to a powder and mixed with quicksilver or mercury. This
+mercury united with both the gold and the silver, making an amalgam.
+The amalgam, together with the finely ground ore, was put into a
+"settler," and here the heavy amalgam sank to the bottom and was then
+strained. The extra mercury was collected, and the amalgam was put
+into a retort or kettle and heated. The mercury became a gas and was
+driven off from the gold and silver, then caught in a vessel cool
+enough to condense it, just as a cold plate held in steam will
+collect drops of water. Sometimes the ore was mixed with copper and
+lead. In that case common salt and copper sulphate were used. Some ore
+had to be roasted in a furnace in order to drive off the sulphur.
+
+[Illustration: THE STORY OF A SPOON
+
+_Courtesy The Gorham Co._
+
+(1) Silver strip blanked. (2) Pinched. (3) Graded. (4) Outlining of
+Handle. (5) Stamped Handle. (6) Spoon completely trimmed. (7, 8)
+Finished spoons.]
+
+There were great and unusual dangers to be met in getting the ore. The
+vein of quartz which bore it was fifty or sixty feet wide. Some was
+hard, and some so soft and crumbling that pillars would not hold up
+the roof. The passageways were then lined with heavy logs standing on
+either side, other logs laid across their tops, and all bolted firmly
+together. Nevertheless, they twisted and fell, and slowly but
+certainly the whole mass of earth and rock, two hundred or more feet
+in thickness, was coming down upon the heads of the miners. The work
+on the Comstock mines had come to an end unless a man could be found
+able to invent some system of support not laid down in the books. The
+man was found. He took short, square timbers five or six feet long,
+put them together as if they were the sides and ends of square boxes,
+and piled them one above another, making hollow pillars. He fastened
+these firmly together and filled the space inside with waste rock,
+thus making strong, solid pillars that would support almost any weight
+that could be put upon them.
+
+There were two other dangers, water and heat. The vein was porous and
+water was constantly trickling out of it. Then, too, there were "water
+pockets," or natural reservoirs in the rock, and any moment the
+stroke of a pick might let out a torrent and force the miners to run
+for their lives. Sometimes minerals were dissolved in this water, and
+the men with closed eyes and swollen faces had to be hurried to the
+surface for treatment. Powerful pumps had to be used and the water
+sent away through long lines of pipes. This water was warm, and in
+very deep workings in the Comstock vein it was boiling hot. Even with
+quantities of ice sent down to cool them, the men could work in some
+places only a short time.
+
+In San Francisco there was a mining engineer named Adolph Sutro who
+planned to remedy these troubles by driving a big four-mile tunnel
+through the heart of the mountain, letting out the hot water and the
+foul air. The owners of some of the mines joined him in raising the
+money, and the tunnel was dug. Through this the water ran out. The
+mines were freed of foul air and fresh air was driven in.
+
+The Comstock lode has given up an amazing amount of precious metal.
+Between 1860 and 1890 it produced $340,000,000. After 1890, however,
+its product grew less. The vein was not so rich, the price of silver
+fell, while the cost of mining it at great depths increased. Not
+nearly so much was mined, and at length water rose in the mines up to
+the level of the Sutro Tunnel. In 1900 new machinery was put in and
+new methods were adopted, such as treating the tailings with cyanide
+and so saving much of the precious metal from them. From the beginning
+the Comstock mines have been so ready to follow improved methods that
+they have been called the mining school of the world.
+
+Great quantities of silver are used for making jewelry and for
+tableware. The one objection to its use is that silver likes to unite
+with sulphur, and thus the silver easily becomes black. There is
+sulphur in the yolk of an egg and that is why the spoon with which it
+has been eaten turns black. Even if silverware is not used, it
+tarnishes, especially in towns, because there is so much sulphureted
+hydrogen in the air. In perfectly pure air, it would not tarnish.
+Silver is harder than gold, but not hard enough to be used without
+some alloy, usually copper. Tableware is "solid" even if it contains
+alloy enough to stiffen it. It is "plated" if it is made of some
+cheaper metal and covered with silver. The old way of doing this was
+to fasten with bits of solder a thin sheet of silver to the cup or
+vase or whatever was in hand and heat it. This did fairly well for
+large, smooth articles; but it was almost impossible to finish the
+edges of spoons so as not to show the two metals. If you look at a
+plated spoon to-day, however, you will find that there is no break at
+the edge, and so far as you can tell by the eye, it is solid silver.
+If you look on the back of the spoon, you will perhaps see "Rogers
+Bros. 1846." These men were the first silvermakers in this country to
+plate tableware by electricity. To make a spoon, they formed one out
+of iron or copper and made sure that it was perfectly clean. Then
+across a bath of silver cyanide, potassium cyanide, and water they
+laid two metal rods, and from these they hung a spoon at one end and a
+plate of silver at the other. These rods were connected with the two
+poles of a battery. The electrical current passed through them,
+released the silver from the silver cyanide, and this was deposited
+upon the spoon. The cyanide that had lost its silver took enough more
+from the silver plate to make up. The amount of silver on the spoon
+depends upon the length of time it remains in the bath. It is weighed
+before plating and again afterwards, to make sure that the proper
+amount of silver has been deposited upon it. On the back of many
+plated articles you will see the words "Triple plate" or "Quadruple
+plate." If the article has been made by a reliable firm, this means
+that the triple plate it manufactures contains three times as much
+silver as "single plate," and that quadruple plate contains four times
+as much. A piece of silver looks just as well if it has stayed in the
+bath only a few minutes, but of course it has taken on so little
+silver that this will soon wear off and show the cheaper metal.
+
+A large amount of silver is used for coins. When the United States
+needs dollars, half-dollars, quarters, and dimes, notice is given and
+offers are called for, stating the quantity for sale and its price.
+When it is delivered, it is first of all "assayed"; that is, tested to
+find out how nearly pure it is and how much it is worth. Next it is
+refined, or purified from other metals, mixed with a little copper to
+harden it, then melted again and poured into moulds to make bars. If
+dollars are to be made, the bar is made thinner by passing it between
+heavy rollers, and blanks for dollars are cut out with a die. These
+blanks are weighed and every one that is too heavy or too light is put
+back to be melted over again. Thus far these dollars are only round,
+smooth pieces of metal. They must be milled to give them a rough edge,
+and they must be stamped. For stamping, the piece of metal is placed
+between two dies, one above and one below, and these close upon it
+with a force of one hundred and fifty tons. Every part of the process
+of manufacturing money is carried on with the utmost care. The places
+where coins are made are called "mints." The United States has four;
+the oldest is in Philadelphia, and there are branch mints in San
+Francisco, New Orleans, and Denver. Coins minted in Philadelphia have
+no distinguishing mark; but coins minted in San Francisco are marked
+with a tiny "S"; if minted in New Orleans, with an "O"; and if in
+Denver, with a "D."
+
+
+
+
+VII
+
+IRON, THE EVERYDAY METAL
+
+
+Did you ever realize that your food and clothes, your books, and the
+house in which you live all depend upon iron? Vegetables, grains, and
+fruits are cultivated with iron tools; fish are caught with iron
+hooks, and many iron articles are used in the care and sale of meat.
+Clothes are woven on iron looms, sewed with iron needles, and fastened
+together with buttons containing iron. Books are printed and bound by
+iron machines, and sometimes written with iron pens or on iron
+typewriters. Houses are put together with nails; and indeed, there is
+hardly an article in use that could be made as well or as easily if
+iron was not plenty. If you were making a world and wanted to give the
+people the most useful metal possible, the gift would have to be iron;
+and the wisest thing you could do would be to put it everywhere, but
+in such forms that the people would have to use their brains to make
+it of service.
+
+This is just the way with the iron in our world. Wherever you see a
+bank of red sand or red clay or a little brook which leaves a red mark
+on the ground as it flows, there is iron. Iron is in most soils, in
+red bricks, in garnets, in ripening apples, and even in your own
+blood. It forms one twentieth part of the crust of the earth. Iron
+dissolves in water if you give it time enough. If you leave a steel
+tool out of doors on a wet night, it will rust; that is, some of the
+iron will unite with the oxygen of the water. This is rather
+inconvenient, and yet in another way this dissolving is a great
+benefit. Through the millions of years that are past, the oxygen of
+the rain has dissolved the iron in the hills and has worked it down,
+so that now it is in great beds of ore or in rich "pockets" that are
+often of generous size. One of them, which is now being mined in
+Minnesota, is more than two miles long, half a mile wide, and of great
+thickness. The rains are still at work washing down iron from the
+hills. They carry the tiny particles along as easily as possible until
+they come upon limestone. Then, almost as if it was frightened, the
+brook drops its iron and runs away as fast as it can. Sometimes it
+flows into a pond or bog in which are certain minute plants or animals
+that act as limestone does, and the particles of iron fall to the
+bottom of the pond. In colonial days much of the iron worked in
+America was taken from these deposits. One kind of iron is of special
+interest because it comes directly from the sky, and falls in the
+shape of stones called "meteorites," some of which weigh many tons. In
+some of the old fables about wonderful heroes, the stories sometimes
+declare that the swords with which they accomplished their deeds of
+prowess fell straight from the heavens, which probably means that they
+were made of meteoric iron. Fortunately for the people and their
+homes, meteorites are not common, but every large museum has
+specimens of them.
+
+It is not especially difficult to make iron if you have the ore, a
+charcoal fire in a little oven of stones, and a pair of bellows. Put
+on layers of charcoal alternating with layers of ore, blow the
+bellows, and by and by you will have a lump of iron. It is not really
+melted, but it can be pounded and worked. This is called the "Catalan
+method," because the people of Catalonia in Spain made iron in this
+way. It is still used by the natives of the interior of Africa. But if
+all the iron was made by this method, it would be far more costly than
+gold. The man who makes iron in these days must have an immense "blast
+furnace," perhaps one hundred feet high, a real "pillar of fire." Into
+this furnace are dropped masses of ore, and with it coke to make it
+hotter and limestone to carry off the silica slag, or worthless part.
+To increase the heat, blasts of hot air are blown into the bottom of
+the furnace. This air is heated by passing it through great steel
+cylinders as high as the furnace. The fuel used is nothing more than
+the gases which come out at the top of the furnace.
+
+The slag is so much lighter than iron that when the ore is melted the
+slag floats on top just as oil floats on water, and can be drained out
+of the furnace through a higher opening than that through which the
+iron flows. The slag tap is open most of the time, but the iron tap is
+opened only once in about six hours. It is a magnificent sight when a
+furnace is "tapped" and the stream of iron drawn off. Imagine a great
+shed, dark and gloomy, with many workmen hurrying about to make ready
+for what is to come. The floor is of sand and slopes down from the
+furnace. Through the center of this floor runs a long ditch straight
+from the furnace to the end of the shed. Opening from it on both sides
+are many smaller ditches; and connecting with these are little
+gravelike depressions two or three feet long and as close together as
+can be. These are called "pigs." When the time has come, the workmen
+gather about the furnace, and with a long bar they drill into the
+hard-baked clay of the tapping hole. Suddenly it breaks, and with a
+rush and a roar the crimson flood of molten iron gushes out. It flows
+down the trench into the ditches, then into the pigs, till their whole
+pattern is marked out in glowing iron. Now the blast begins to drive
+great beautiful sparks through the tapping hole. This means that the
+molten iron is exhausted. The blast is turned off, and the "mud-gun"
+is brought into position and shoots balls of clay into the tapping
+hole to close it for another melting, or "drive." The crimson pigs
+become rose-red, darken, and turn gray. The men play streams of water
+over them and the building is filled with vapor. As soon as the pigs
+are cool enough, they are carted away and piled up outside the
+building.
+
+In some iron works moulds of pressed steel carried on an endless chain
+are used instead of sand floors. The chain carries them past the mouth
+of a trough full of melted iron. They are filled, borne under water
+to be cooled, and then dropped upon cars. A first-class machine can
+make twenty pigs a minute.
+
+[Illustration: IN THE STEEL FOUNDRY
+
+It is a dangerous business to visit a steel mill. Tremendous kettles
+travel overhead on huge cranes, hot metal flows from unexpected
+places, and there is a constant glow and steam and roar everywhere to
+confuse the unwary.]
+
+Most of the iron made in blast furnaces is turned into steel. Steel
+has been made for centuries, but until a few years ago the process was
+slow and costly. A workman's steel tools were treasures, and a good
+jackknife was a valuable article. Railroads were using iron rails.
+They soon wore out, but at the suggestion to use steel, the presidents
+of the roads would have exclaimed, "Steel, indeed! We might as well
+use silver!" Trains needed to be longer and heavier, but iron rails
+and bridges could not stand the strain. Land in cities was becoming
+more valuable; higher buildings were needed, but stone was too
+expensive. Everywhere there was a call for a metal that should be
+strong and cheap. Iron was plentiful, but steel was dear. A cheaper
+method of making iron into steel was needed; and whenever there is
+pressing need of an invention, it is almost sure to come. Before long,
+what is known as the "Bessemer process" was invented. One great
+difficulty in the manufacture of steel was to leave just the right
+amount of carbon in the iron. Bessemer simply took it all out, and
+then put back exactly what was needed. Molten iron, tons and tons of
+it, is run into an immense pear-shaped vessel called a "converter."
+Fierce blasts of air are forced in from below. These unite with the
+carbon and destroy it. There is a roar, a clatter, and a clang.
+Terrible flames of glowing red shoot up. Suddenly they change from red
+to yellow, then to white; and this is the signal that the carbon has
+been burned out. The enormously heavy converter is so perfectly poised
+that a child can move it. The workmen now tilt it and drop in whatever
+carbon is needed. The molten steel is poured into square moulds,
+forming masses called "blooms," and is carried away. More iron is put
+into the converter, and the work begins again.
+
+The Bessemer process makes enormous masses of steel and makes it very
+cheaply; but it has one fault--it is too quick. The converter roars
+away for a few minutes, till the carbon and other impurities are
+burned out; and the men have no control over the operation. In what is
+called the "open-hearth" process, pig iron, scrap iron, and ore are
+melted together with whatever other substances may be needed to make
+the particular kind of steel desired. This process takes much longer
+than the Bessemer, but it can be controlled. Open-hearth steel is more
+homogeneous,--that is, more nearly alike all the way through,--and is
+better for some purposes, while for others the Bessemer is preferred.
+
+Steel is hard and strong, but it has two faults. A steel bar will
+stand a very heavy blow and not break, but if it is struck gently many
+thousand times, it sometimes crystallizes and may snap. A steel rail
+may carry a train for years and then may crystallize and break and
+cause a wreck. Inventors are at work discovering alloys to prevent
+this crystallization. The second fault of steel is that it rusts and
+loses its strength. That is why an iron bridge or fence must be kept
+painted to protect it from the moisture in the air.
+
+If all the iron that is in use should suddenly disappear, did you ever
+think what would happen? Houses, churches, skyscrapers, and bridges
+would fall to the ground. Railroad trains, automobiles, and carriages
+would become heaps of rubbish. Ships would fall apart and become only
+scattered planks floating on the surface of the water. Clocks and
+watches would become empty cases. There would be no machines for
+manufacturing or for agriculture, not even a spade to dig a garden.
+Everybody would be out of work. If you wish to see how it would seem,
+try for an hour to use nothing that is of iron or has been made by
+using iron.
+
+
+
+
+VIII
+
+OUR GOOD FRIEND COPPER
+
+
+Where did rocks come from?
+
+Some were deposited in water, like limestone and like the shale and
+sandstone that lie over the strata of coal. Others were made by fire,
+and were thrown up in a melted state from the interior of the earth.
+Such rocks are the Giant's Causeway in Ireland and the Palisades of
+the Hudson River. They are called "igneous" rocks, from the Latin word
+_ignis_ meaning "fire."
+
+When the igneous rocks were thrown up to the surface of the earth,
+they brought various metals with them. How the metals happened to be
+there ready to be brought up, no one knows. Some people think they
+were dissolved in water and then deposited; others think that
+electricity had something to do with their formation. However that may
+be, metals were brought up with the igneous rocks, and one of these
+metals is copper.
+
+Now, to one who did not know how to work iron, copper was indeed a
+wonderful treasure, for it made very good knives and spoons. The
+people who lived in this country long before the Indians came
+understood how to use it, and after a while the Indians themselves
+found out its value. They did not trouble themselves to dig for it;
+they simply picked it up from the ground, good pure metal in lumps;
+and with stones for hammers they beat it into knives.
+
+There was only one place in what is now the United States where they
+could do this, and that was in northern Michigan. A long point of land
+stretches out into Lake Superior as if it was trying to see what could
+be found there. Just beyond its reach is Isle Royal; and in these two
+places there was plenty of copper, enough for the Indians, enough for
+the people who have come after them, and enough for a great many more.
+One piece of copper which the Indians did not pick up, and the United
+States Government did, is the famous Ontonagon Boulder, so called
+because it was found near the Ontonagon River. It weighs more than
+three tons. The Indians would have been glad to make use of it, but it
+was too hard for their tools, and so they are said to have worshiped
+it as a god. It is now in the National Museum in Washington.
+
+The lumps of copper, such as those which delighted the hearts of the
+Indians, are known to-day as "barrel" copper, because they are of a
+good size to be dropped into barrels and carried away for smelting.
+The great boulders which the Indians could not use are called "mass"
+copper. Sometimes they weigh as much as five hundred tons. The copper
+in them is almost pure, and a big boulder is worth perhaps $200,000.
+Nevertheless, the mine-owners do not rejoice when they come upon such
+a mass in their digging, for it cannot be either dug or blasted, and
+has to be cut away with chisels of chilled steel. Now, a mine may be
+wonderfully rich in metal, but if working it costs too much, then
+another mine with less metal but more easily worked will pay better.
+So it is with these great masses of copper. They are interesting to
+study and they look well in museums, but they do not pay so well as
+the "stamp" copper which is found in humble little bits in the gangue,
+or the rock of the vein, and has to be pounded in a stamp mill. This
+gangue is dug out and broken up as in mines of other metals. The
+copper is much heavier than the rock, so it is easy to get rid of the
+worthless gangue by means of a flow of water. The gangue of the
+Michigan mines is exceedingly hard, but the stamps are so powerful
+that one can crush five hundred tons in less than twenty-four hours.
+Some copper can be taken out of the mortars at once, but the rest of
+the broken gangue is fed to jigs, or screens, which are kept under
+jets of water. The water is thrown up from below and the lighter rock
+is tossed away, while the heavier copper falls through the tiny holes
+in the screens.
+
+[Illustration: IN A COPPER SMELTER
+
+The men are pouring hot copper into moulds for castings.]
+
+After the ore has been through all these experiences, it comes out
+looking like dark-colored sand or coarse brown sugar. It is not
+interesting, and no one who saw it for the first time would ever fancy
+that it was going to turn into something beautiful. It is dumped into
+freight cars and trundled off to the smelting furnaces. But however
+uninteresting it looks, it is well worth while to follow these cars to
+see what happens to it at the smelters. First of all, even before it
+goes into the smelting furnace, it must be roasted. There is usually
+sulphur combined with the copper, and roasting will get rid of much of
+it. In some places this is done by building up a great heap of ore
+with a little wood. The wood is kindled, and by the time it has burned
+out, the sulphur in the ore has begun to burn, and in a good-sized
+heap it will continue to burn for perhaps two months.
+
+Such a heap is a good thing to keep away from, for the fumes of
+sulphur are very disagreeable. Indeed, they will kill trees and other
+growing things wherever the wind may carry them, even several miles
+away. The managers of mines of copper as well as of gold and silver
+have learned to economize; and it has been found that instead of
+letting these fumes go into the air, they may be made to pass through
+acid chambers lined with zinc and full of water. The water holds the
+fumes, and can be used in making sulphuric acid.
+
+After the ore has been roasted, it is put into the furnace for
+smelting. If you should make an oven and put into it a mixture of wood
+and roasted copper, that would be a smelting furnace. Set the wood on
+fire, pump in air to make the flame hot, and if your furnace could be
+made hot enough,--that is, 2300 deg. F., or about eleven times as hot as
+boiling water,--you could smelt copper. Of course the furnace of a
+real smelting factory will hold tons and tons of copper ore and has
+all sorts of improvements, but after all it is in principle only an
+oven with wood and ore and draft. Another sort of furnace, which is
+better for some kinds of ore, has a grate for the fire and a bed above
+it for the copper.
+
+Imagine an enormous furnace holding between two and three hundred tons
+of metal and burning with such a terrific heat that by contrast
+boiling water would seem cool and comfortable. Suddenly, while you
+stand looking at it, but a long way off, a door flies open and the
+most beautiful cascade--only it is not a waterfall, but a _copper_
+fall--pours out. It looks like red, red gold, rich and wonderful, with
+little flames of red and blue dancing over it. It might almost be one
+of the fire-breathing dragons of the old story-books; and if it should
+get loose, it would devour whomever it touched far quicker than any
+dragon. It hardly seems as if any one could manage such a monster; but
+it looks easy, after you have seen it done. An enormous horizontal
+wheel revolves slowly. On its edge are moulds shaped like bricks, but
+much larger. On the hub of the wheel a workman sits to direct the
+filling of these. A set of them is filled, and moves on, and others
+take their place. When they are partly cooled, another workman, at the
+farther side of the wheel, pries them out of the mould and drops them
+into water. Then by the aid of the fingers of a machine and those of
+men, they are loaded upon cars.
+
+In copper there is often some gold and silver. The precious metals do
+not make the copper any better, and if they can be separated from it,
+they are well worth the trouble. This is done by electricity. It is so
+successful that the metallurgists are hoping soon to take a long step
+ahead and by means of electricity to produce refined copper directly
+from the ore. Indeed, this has been done already in the laboratories,
+but before the managers of mines can employ the method, a way of
+making it less expensive must be discovered.
+
+No mine that wastes anything is as well managed as it might be; and
+superintendents are constantly on the watch for cheaper methods and
+for ways to make the refuse matter of use. Even the scoria, or slag
+from the furnaces, has been found to be good for something, and now it
+is made into a coarse sort of brick that for certain rough uses is of
+value. By the way, the shaft of a copper mine, the Red Jacket, has
+shown itself of use in a manner that no one expected, namely, it helps
+to prove that the earth turns around. This shaft is the deepest mining
+shaft in the world, and when you get into the cage, you go down a full
+mile toward the center of the earth. If you drop any article into the
+shaft, it always strikes the east side before reaching the bottom. The
+only way to explain this is that the earth turns toward the east.
+
+Copper mixed with zinc forms brass, which is harder than copper alone.
+It tarnishes, though not so easily as copper; but a coat of varnish
+will protect it till the varnish wears off. A good way to find out the
+many uses of brass and to see how valuable they are is to go along the
+street and through a house and make a list. On the street you will see
+signs, harness buckles, and buttons, everywhere. Look on the
+automobiles and fire engines for a fine display of brass, polished and
+shining. In the house you will find brass bedsteads, curtain rods,
+faucets, pipes, drawerpulls, candlesticks, gas and electric fixtures,
+lamps, the works of clocks and watches, and scores of other things.
+You will not have any idea how many they are till you begin to count.
+
+Copper mixed with tin forms bronze. Go into a hardware store and look
+at the samples of bronze outside of each drawer, and you will be
+surprised that there are so many. Bronze does not change even when in
+the open air for ages. That is one reason why it has always been so
+much used for statues. There are two strange facts about this mixture.
+One is that bronze is harder than either copper or tin. The other is
+that if you mix one pint of melted copper with one pint of tin, the
+mixture will be less than a quart. Just why these things are so, no
+one is quite certain. Mathematics declares that the whole is equal to
+the sum of its parts; but in this one case the whole seems to be less
+than the sum of its parts.
+
+Another reason why bronze is so much used for statues is that the
+castings are smooth. I once went to a foundry to have a brass ornament
+shaped somewhat like a cone made for a clock. The foundryman formed a
+mould in clay and poured the melted brass into it. When it had cooled,
+the mould was broken off and the ornament taken out; but it was of no
+use because it was so full of little hollows that it could not be made
+smooth without cutting away a great deal of it. The man had to try
+three times before he succeeded in making one that could be polished.
+If it had been made of bronze, there would have been no trouble,
+because bronze, hard as it is after it cools, flows when it is melted
+almost as easily as molasses and fills every little nook and corner of
+the mould.
+
+A famous Latin poet named Horace, who lived two thousand years ago,
+wrote of his poems, "I have reared a monument more lasting than
+bronze"; and he was right, for few statues have endured from his day
+to ours, but his poems are still read and admired.
+
+Bells are made of bronze, about three quarters copper and one quarter
+tin. It is thought that much copper gives a deep, full tone, and that
+much tin with, sometimes, zinc makes the tone sharp. The age of a bell
+has something to do with its sound being rich and mellow; but the
+bellmaker has even more, for he must understand not only how to cast
+it, but also how to tune it. If you tap a large bell, it will, if
+properly tuned, sound a clear note. Tap it just on the curve of the
+top, and it will give a note exactly one octave above the first. If
+the note of the bell is too low, it can be made higher by cutting away
+a little from the inner rim. If it is too high, it can be made lower
+by filing on the inside a little above the rim. Many of the old bells
+contain the gifts of silver and gold which were thrown in by people
+who watched their founding. The most famous bell in the United States
+is the "Liberty Bell" of Independence Hall, in Philadelphia, which
+rang when Independence was adopted by Congress. This was founded in
+England long before the Revolution and later was melted and founded
+again in the United States.
+
+It would not be easy to get on without brass and bronze; but even
+these alloys are not so necessary as copper by itself. It is so strong
+that it is used in boiler tubes of locomotives, as roofing for
+buildings and railroad coaches, in the great pans and vats of the
+sugar factories and refineries. A copper ore called "malachite," which
+shows many shades of green, beautifully blended and mingled, is used
+for the tops of tables. Wooden ships are often "copper-bottomed"; that
+is, sheets of copper are nailed to that part of the hull which is
+under water in order to prevent barnacles from making their homes on
+it, and so lessening the speed of the vessel.
+
+People often say that the latter half of the nineteenth century was
+the Age of Steel, because so many new uses for steel were found at
+that time. The twentieth century promises to be the Age of
+Electricity, and electricity must have copper. Formerly iron was used
+for telegraph wires; but it needs much more electricity to carry power
+or light or heat or a telegraphic message over an iron wire than one
+of copper. Moreover, iron will rust and will not stretch in storms
+like copper, and so needs renewing much oftener. Electric lighting and
+the telephone are everywhere, even on the summits of mountains and in
+mines a mile below the earth's surface. Electric power, if a
+waterfall furnishes the electricity, is the cheapest power known. The
+common blue vitriol is one form of copper, and to this we owe many of
+our electric conveniences. It is used in all wet batteries, and so it
+rings our doorbells for us. It also sprays our apple and peach trees,
+and is a very valuable article. Indeed, copper in all its forms, pure
+and alloyed, is one of our best and most helpful friends.
+
+
+
+
+IX
+
+THE NEW METAL, ALUMINUM
+
+
+Not many years ago a college boy read about an interesting metal
+called "aluminum." It was as strong as iron, but weighed only one
+third as much, and moisture would not make it rust. It was made of a
+substance called "alumina," and a French chemist had declared that the
+clay banks were full of it; and yet it cost as much as silver. It had
+been used in France for jewelry and knicknacks, and a rattle of it had
+been presented to the baby son of the Emperor of France as a great
+rarity.
+
+The college boy thought by day and dreamed by night of the metal that
+was everywhere, but that might as well be nowhere, so far as getting
+at it was concerned. At the age of twenty-one, the young man
+graduated, but even his new diploma could not keep his mind away from
+aluminum. He borrowed the college laboratory and set to work. For
+seven or eight months he tried mixing the metal with various
+substances to see if it would not dissolve. At length he tried a stone
+from Greenland called "cryolite," which had already been used for
+making a kind of porcelain. The name of this stone comes from two
+Greek words meaning "ice stone," and it is so called because it melts
+so easily. The young student melted it and found that it would
+dissolve alumina. Then he ran an electric current through the melted
+mass, and there was a deposit of aluminum. This young man, just out of
+college, had discovered a process that resulted in reducing the cost
+of aluminum from twelve dollars a pound to eighteen cents. Meanwhile a
+Frenchman of the same age had been working away by himself, and made
+the same discovery only two months later.
+
+Aluminum is now made from a mineral called "bauxite," found chiefly in
+Georgia, Alabama, and Arkansas. Mining it is much more agreeable than
+coal mining, for the work is done aboveground. The bauxite is in beds
+or strata which often cover the hills like a blanket. First of all,
+the mine is "stripped,"--that is, the soil which covers the ore is
+removed,--and then the mining is done in great steps eight or ten feet
+high, if a hill is to be worked. There is some variety in mining
+bauxite, for it occurs in three forms. First, it may be a rock, which
+has to be blasted in order to loosen it. Second, it may be in the form
+of gray or red clay. Third, it occurs in round masses, sometimes no
+larger than peas, and sometimes an inch in diameter. In this form it
+can easily be loosened with a pickaxe, and shoveled into cars to be
+carried to the mill. Bauxite is a rather mischievous mineral and
+sometimes acts as if it delighted in playing tricks upon managers of
+mines. The ore may not change in the least in its appearance, and yet
+it may suddenly have become much richer or much poorer. Therefore the
+superintendent has to give his ore a chemical test every little while
+to make sure that all things are going on well.
+
+This bauxite is purified, and the result is a fine white powder, which
+is pure alumina, and consists of the metal aluminum and the gas
+oxygen. Cryolite is now melted by electricity. The white powder is put
+into it, and dissolves just as sugar dissolves in water. The
+electricity keeps on working, and now it separates the alumina into
+its two parts. The aluminum is a little heavier than the melted
+cryolite, and therefore it settles and may be drawn off at the bottom
+of the melting-pot.
+
+There are a good many reasons why aluminum is useful. As has been said
+it is strong and light and does not rust in moisture. You can beat it
+into sheets as thin as gold leaf, and you can draw it into the finest
+wire. It is softer than silver, and it can be punched into almost any
+form. It is the most accommodating of metals. You can hammer it in the
+cold until it becomes as hard as soft iron. Then, if you need to have
+it soft again, it will become so by melting. It takes a fine polish
+and is not affected, as silver is, by the fumes which are thrown off
+by burning coal; and so keeps its color when silver would turn black.
+Salt water does not hurt it in the least, and few of the acids affect
+it. Another good quality is that it conducts electricity excellently.
+It is true that copper will do the same work with a smaller wire; but
+the aluminum is much lighter and so cheap that the larger wire of
+aluminum costs less than the smaller one of copper, and its use for
+this purpose is on the increase. It conducts heat as well as silver.
+If you put one spoon of aluminum, one of silver, and one that is
+"plated" into a cup of hot water, the handles of the first two will
+almost burn your fingers before the third is at all uncomfortable to
+touch.
+
+[Illustration: A "MOVIE" OF AN ALUMINUM FUNNEL
+
+_Courtesy The Aluminum Cooking Utensil Company._
+
+Seventeen other operations are necessary after the thirteenth stamping
+operation before the funnel is ready to be sold. And after all this
+work, we can buy it for 35 cents at any hardware store.]
+
+Aluminum is found not only in clay and indeed in most rocks except
+sandstone and limestone, but also in several of the precious stones,
+in the yellow topaz, the blue sapphire and lapis-lazuli, and the red
+garnet and ruby. It might look down upon some of its metallic
+relatives, but it is friendly with them all, and perfectly willing to
+form alloys with most of them. A single ounce of it put into a ton of
+steel as the latter is being poured out will drive away the gases
+which often make little holes in castings. Mixed with copper it makes
+a beautiful bronze which has the yellow gleam of gold, but is hard to
+work. When a piece of jewelry looks like gold, but is sold at too low
+a price to be "real," it may be aluminum bronze, very pretty at first,
+but before long its luster will vanish. Aluminum bronze is not good
+for jewelry, but it is good for many uses, especially for bearings in
+machinery. Aluminum mixed with even a very little silver has the color
+and brightness of silver. The most common alloys with aluminum are
+zinc, copper, and manganese, but in such small quantities that they do
+not change its appearance.
+
+With so many good qualities and so few bad ones, it is small wonder
+that aluminum is employed for more purposes than can be counted. A
+very few years ago it was only an interesting curiosity, but now it is
+one of the hardest-worked metals. Automobiles in particular owe a
+great deal to its help. When they first began to be common, in
+1904-05, the engines were less powerful than they are now made, and
+aluminum was largely employed in order to lessen the weight. Before
+long it was in use for carburetors, bodies, gear-boxes, fenders,
+hoods, and many other parts of the machine. Makers of electric
+apparatus use aluminum instead of brass. The frames of opera glasses
+and of cameras are made of it. Travelers and soldiers and campers,
+people to whom every extra ounce of weight counts, are glad enough to
+have dishes of aluminum. The accommodating metal is even used for
+"wallpaper," and threads of it are combined with silk to give a
+specially brilliant effect on the stage. It can be made into a paint
+which will protect iron from rust; and will make woodwork partially
+fireproof.
+
+Aluminum has been gladly employed by the manufacturers of all sorts of
+articles, but nowhere has its welcome been more cordial than in the
+kitchen. Any one who has ever lifted the heavy iron kettles which were
+in use not so very many years ago will realize what an improvement it
+is to have kettles made of aluminum. But aluminum has other advantages
+besides its lightness. If any food containing a weak acid, like
+vinegar and water, is put into a copper kettle, some of the copper
+dissolves and goes into the food; acid does not affect aluminum except
+to brighten it if it has been discolored by an alkali like soda. "Tin"
+dishes, so called, are only iron with a coating of tin. The tin soon
+wears off, and the iron rusts; aluminum does not rust in moisture. A
+strong alkali will destroy it, but no alkali in common use in the
+kitchen is strong enough to do more harm than to change the color, and
+a weak acid will restore that. Enameled ware, especially if it is
+white, looks dainty and attractive; but the enamel is likely to chip
+off, and, too, if the dish "boils dry," the food in it and the dish
+itself are spoiled. Aluminum never chips, and it holds the heat in
+such a manner as to make all parts of the dish equally hot. Food,
+then, is not so likely to "burn down," but if it does, only the part
+that sticks will taste scorched; and no matter how many times a dish
+"boils dry," it will never break. If you make a dent in it, you can
+easily pound it back into shape again. It is said that an aluminum
+teakettle one sixteenth of an inch in diameter can be bent almost
+double before it will break.
+
+Aluminum dishes are made in two ways. Sometimes they are cast, and
+sometimes they are drawn on a machine. If one is to be smaller at the
+top, as in the case of a coffeepot, it is drawn out into a cylinder,
+then put on a revolving spindle. As it whirls around, a tool is held
+against it wherever it is to be made smaller, and very soon the
+coffeepot is in shape. The spout is soldered on, but even the solder
+is made chiefly of aluminum.
+
+Aluminum dishes may become battered and bruised, but they need never
+be thrown away. There is an old story of some enchanted slippers which
+brought misfortune to whoever owned them. The man who possessed them
+tried his best to get rid of the troublesome articles, but they always
+returned. So it is with an aluminum dish. Bend it, burn it, put acid
+into it, do what you will to get rid of it, but like the slippers it
+remains with you. Unlike them, however, it brings good fortune,
+because it saves time and trouble and patience and money.
+
+A few years ago the motive power for most manufactures was steam.
+Electricity is rapidly taking its place; and if aluminum was good for
+nothing else save to act as a conductor of electricity in its various
+applications, there would even then be a great future before it.
+
+
+
+
+X
+
+THE OIL IN OUR LAMPS
+
+
+Probably the first man who went to a spring for a drink and found oil
+floating on the water was decidedly annoyed. He did not care in the
+least where the oil came from or what it was good for; he was thirsty,
+and it had spoiled his drink, and that was enough for him. We know now
+that oil comes chiefly from strata of coarse sandstone, but we are not
+quite sure how it happened to be there. The sand which formed these
+strata was deposited by water ages and ages ago--we are certain of
+that. Another thing that we are certain of is that where the strata
+lie flat, there is no oil. Hot substances become smaller as they cool;
+and as the earth grew cooler, it became smaller. The crust of the
+earth wrinkled as the skin of an apple does when it dries. In the tops
+of these great sandstone wrinkles there is often gas; and below the
+gas is the place where oil is found. There is no use in looking for
+petroleum where the folds of the strata are very sharp, because in
+that case the strata crack and let the oil flow away. It is not in
+pools, but the porous stone holds it just as a sponge holds water. If
+you drop a little oil upon a stone even much less porous than
+sandstone, it will not be easy to wipe it off, because some of it will
+have sunk into the stone.
+
+In many places the gas forces its way out, and is piped to carry to
+houses for light and heat. Not far above Niagara Falls there was a
+spring of gas which flowed for years. An iron pipe was put down, and
+when the gas was lighted, the flame shot up three or four feet. The
+gas came with such force that a handkerchief put over the end of the
+pipe would not burn, though the flame would blaze away above it. In
+the country of the fire worshipers, on the shores of the Caspian Sea,
+fires of natural gas have been burning for ages, kindled, perhaps, by
+lightning centuries ago. There is a vast supply of oil in this place;
+and indeed there is hardly a country that has not more or less of it.
+
+In the United States the colonists soon learned that there was
+petroleum in what is now the State of New York; but New York was a
+long way from the Atlantic seaboard in those days, and they went on
+contentedly burning candles or sperm whale oil, or, a little later, a
+rather dangerous liquid which was known as "fluid." The Indians
+believed that the oil which appeared in the springs was a good
+medicine. They threw their blankets upon the water, and when these had
+become saturated with the oil, they wrung them out and sold the oil.
+Those were the times when if a medicine only tasted and smelled bad
+enough, people never doubted that it would cure all their diseases,
+and they gladly bought the oil of the Indians.
+
+When at last it became clear to the members of an enterprising company
+that oil for use in lamps could be made from petroleum, they secured
+some land in Pennsylvania that seemed promising and set to work to
+dig a well. But the more they dug, the more the loose dirt fell in
+upon them. Fortunately for the company, the superintendent had brains,
+and he thought out a way to get the better of the crumbling soil. He
+simply drove down an iron pipe to the sandstone which contained the
+oil, and set his borer at work within the pipe. One morning he found
+that the oil had gushed in nearly to the top of the well. He had
+"struck oil."
+
+This was about ten years after the rush to California for gold, and
+now that this cheaper and quicker method of making a well had been
+invented, there was almost as much of a rush to Pennsylvania for oil.
+With every penny that they could beg or borrow, people from the East
+hurried to the westward to buy or lease a piece of land in the hope of
+making their fortunes. A song of the day had for its refrain,--
+
+    "Stocks par, stocks up,
+      Then on the wane;
+    Everybody's troubled with
+      Oil on the brain."
+
+In the course of a year or two, the first "gusher" was discovered. The
+workmen had drilled down some four or five hundred feet and were
+working away peacefully, when a furious stream of oil burst forth
+which hurled the tools high up into the air. Hundreds of barrels
+gushed out every day, and soon other gushers were discovered. The most
+famous one in the world is at Lakeview, California. For months it
+produced fifty thousand barrels of oil a day, and threw it up three
+hundred and fifty feet into the air in a black column, spraying the
+country with oil for a mile around. The oil flowed away in a river,
+and for a time no one could plan any way to stop it or store it. At
+last, however, a mammoth tank was built around the well and made firm
+with stones and bags of earth. This was soon full of oil; and with all
+this vast weight of oil pressing down upon it, the stream could not
+rise more than a few feet above the surface. Just why oil should come
+out with such force, the geologists are not quite certain; but it is
+thought to result from a pressure of gas upon the sandstone containing
+it. The flow almost always becomes less and less, and after a time the
+most generous well has to be pumped.
+
+[Illustration: A CALIFORNIA OIL FIELD
+
+For scenery, one should not go to an oil field. Looks, smell, and oil
+alike are unpleasant, but every oil derrick covers a fortune and helps
+to make our machinery run smoothly.]
+
+An "oil field" may extend over thousands of square miles; but within
+this field there are always "pools"; that is, certain smaller fields,
+where oil is found. When a man thinks there is oil in a certain spot,
+sometimes he buys the land if he is able; but oftener he gets
+permission of the owner to bore a well, agreeing to pay him a royalty;
+that is, a certain percentage of all the oil that is produced. When
+this has been arranged, he builds his derrick. This consists of four
+strong upright beams firmly held together by crossbeams. It stands
+directly over the place where the well is to be dug. It is from thirty
+to eighty feet in height, according to the depth at which it is hoped
+to find oil. There must also be an engine house to provide the power
+for drilling. An iron pipe eight or ten inches in diameter is driven
+down through the soil until it comes to rock. Now the regular drilling
+begins. At the top of the derrick is a pulley. Over the pulley passes
+a stout rope to which the heavy drilling tools--the "string of tools,"
+as they are called--are fastened. The drilling goes on day and night.
+The drill makes the hole, and the sand pump sucks out the water and
+loose bits of stone. When the drill has gone to the bottom of the
+strata which carry water, the sides of the bore are cased to keep the
+water out; then the drilling continues, but now the drill makes its
+way into the oil-bearing sandstone.
+
+There is nothing certain about the search for oil. In some places it
+is near the surface, in others it is perhaps three or four thousand
+feet down. The well may prove to be a gusher and pour out hundreds of
+thousands of gallons a day; or the oil may refuse to rise to the
+surface and have to be pumped out even at the first. Naturally, no one
+is prepared for a gusher, and millions of gallons have often flowed
+away before any arrangements could be made for storing the oil.
+Sometimes a well that gives only a moderate flow can be made to yield
+generously by exploding a heavy charge of dynamite at the bottom, to
+break up the rock and, it is always hoped, to open some new
+oil-holding crevice that the drill has not reached.
+
+Crude petroleum is a dark, disagreeable, bad-smelling liquid; and
+before it can be of much use, it must be refined. For several years it
+was carried in barrels from the oil fields to Pittsburgh by wagon and
+boat, a slow, expensive process, and generally unsatisfactory to all
+but the teamsters. Then came the railroads. They provided iron tanks
+in the shape of a cylinder fastened to freight cars, much like those
+employed to-day. There was only one difficulty about sending oil by
+rail, and that was that it still had to be hauled by team to the
+railroad, sometimes a number of miles. At length, some one said to
+himself, "Why cannot we simply run a pipe directly from the well to
+the railroad?" This was done. Pumping engines were put in a few miles
+apart, and the invention was a success in the eyes of all but the
+teamsters. In spite of their opposition, however, pipe-lines
+increased.
+
+Before this it had been necessary to build the refineries as near the
+oil regions as possible in order to save the expense of carrying the
+oil; but now they could be built wherever it was most convenient.
+To-day oil can be brought at a small expense from west of the
+Mississippi River to the Atlantic seaboard, refined, and distributed
+throughout that part of the country, or loaded into "tankers,"--that
+is, steamships containing strong tanks of steel,--and so taken across
+the ocean. The pipes are made of iron and are six or eight inches or
+more in diameter. In using them one difficulty was found which has
+been overcome in an ingenious fashion. Sometimes they become choked by
+the impurities of the oil and the flow is lessened. Then a "go-devil"
+is put into them. This is shaped like a cartridge, is about three
+feet in length, composed of springs and plates of iron and so flexible
+that it can turn around a corner. It is so made that as it slips down
+the current of oil, it whirls around and in so doing its nose of sharp
+blades scrapes the pipes clean.
+
+The pipes go over hills and through swamps. They cross rivers
+sometimes by means of bridges, and sometimes they are anchored to the
+bed of the stream. If they have to go through a salt marsh, they are
+laid in concrete to preserve the iron. If these lines were suddenly
+destroyed and oil had to be carried in the old way, kerosene would
+become an expensive luxury.
+
+Getting the oil out of the ground and carried to the refineries is not
+all of the business by any means. The early oils crusted on the lamp
+wicks, their smell was unendurable, and they were given to exploding.
+Evidently, if oil was to be used for lighting, it must be improved,
+and the first step was to distil it. To distil anything means to boil
+it and collect the vapor. If you hold a piece of cold earthenware in
+the steam of a teakettle, water will collect on it. This is distilled
+water, and is purer than that in the kettle. Petroleum was at first
+distilled in a rough way; but now it is done with the utmost care and
+exactness. The crude oil is pumped into boilers holding six hundred
+barrels or more. The fires are started, and the oil soon begins to
+turn into vapor. This vapor passes through coils of pipe or long,
+straight, parallel pipes. Cold water is pumped over these pipes, the
+vapor turns into a liquid again, and we have kerosene oil.
+
+This is the outline of the process, but it is a small part of the
+actual work in all its details. Kerosene oil is only one of the many
+substances found in petroleum. Fortunately, some of these substances
+are light, like gasoline and benzine; some, like kerosene, are
+heavier; and paraffin and tar are heaviest of all. There are also
+gases, which pass off first and are saved to help keep the furnace
+going. Then come the others, one by one, according to their weight.
+The stillman keeps close watch, and when the color and appearance of
+the distillate changes, he turns it off into another tank. This
+process is called "fractional distillation," and the various products
+are called "fractions." No two kinds of petroleum and no two oil wells
+are just alike, and it needs a skillful man to manage either.
+
+Even after all this distillation, the kerosene still chars the wick
+somewhat--which prevents the wick from drawing up the oil
+properly--and it still has a disagreeable smell. To fit it for burning
+in lamps, it must be treated with sulphuric acid, which carries away
+some of the impurities, and then with caustic soda, which carries away
+others. Before it can be put on the market, it is examined to see
+whether it is of the proper color. Then come three important tests.
+The first is to see that it is of the proper weight. If it is too
+heavy, it will not burn freely enough; if it is too light, then there
+is too much of the lighter oils in it for safety. The second test is
+the "flash test." The object of this is to see how hot the oil must be
+before it gives off a vapor which will burn. The third, the "burning
+test," is to discover how hot the oil must be before it will take fire
+and burn on the surface. Most civilized countries make definite laws
+forbidding the sale of kerosene oil that is not up to a standard of
+safety. Oil for use in lamps should have an open flash test of at
+least 100 deg. F. and a burning point of not less than 125 deg. F.
+
+We say that we burn oil in our lamps, but what we really do is to heat
+the oil until it gives off gas, and then we burn the gas. To keep the
+flame regular and help on the burning, we use a chimney on the lamp.
+The hot air rises in the chimney and the cold air underneath rushes in
+to take its place and brings oxygen to the flame. In a close, stuffy
+room no lamp will give a good clear light, because there is not oxygen
+enough for its flame. Let in fresh air, and the light will be
+brighter. If you hold a cold plate in the flame before the chimney is
+put on, soot or carbon will be deposited. A lamp gives light because
+these particles of carbon become so hot that they glow. In lamps using
+a "mantle," there is the glow not only of these particles, but also of
+the mantle. In a wax candle, we light the wick, its heat melts the wax
+and carries it to the flame. When the wax is made hot enough, it
+becomes gas, and we burn the gas, not the wax. Wax alone will melt,
+but not take fire even if a burning match is held to it. The reason is
+that the match does not give heat enough to turn the wax into gas. But
+put a bit of wax upon a bed of burning coals, where there is a good
+supply of heat, and it will turn into gas and burn.
+
+The products made from petroleum are as different in their character
+and uses as paraffin and naphtha. Some of them are used for oiling
+machinery; tar is used for dyes; naphtha dissolves resin to use in
+varnish; benzine is the great cleanser of clothes, printers' types,
+and almost everything else; gasoline runs automobiles, motors, and
+many sorts of engines; paraffin makes candles, seals jelly glasses,
+covers the heads of matches so that they are no longer spoiled by
+being wet, and makes the ever-useful "waxed paper"; printers' ink and
+waterproof roofing-paper both owe a debt to petroleum. Even in
+medicine, though a little petroleum is no longer looked upon as a
+cure-all, vaseline, one of its products, is of great value. It can be
+mixed with drugs without changing their character, and it does not
+become rancid. For these reasons, salves and other ointments can be
+mixed with it and preserved for years.
+
+
+
+
+XI
+
+LITTLE GRAINS OF SALT
+
+
+The most interesting mine in the world is that of Wieliczka in Poland.
+In it there are some thirty miles of streets and alleys; there are
+churches with pillars, shrines, and statues; there are stairs,
+monuments, and restaurants; there is a ballroom three hundred feet
+long and one hundred and ninety feet high, with beautiful chandeliers,
+and in it is a carven throne whereon the Emperor Franz Joseph sat when
+he visited the mine. There are lakes crossed by ferryboats. There is a
+railroad station for the mule trains which bear the precious mineral
+salt, for this is a salt mine, and shrines, statues, churches,
+chandeliers--everything--are all cut out of salt.
+
+This mine has been worked for at least eight hundred years and still
+has salt enough to supply all Europe for ages. The mass of salt is
+believed to be five hundred miles long, fifty miles wide, and nearly a
+quarter of a mile thick. It is so pure that it is sold just as it
+comes from the mine, either in blocks or finely ground. This mine is a
+wonderful place to visit, almost like an enchanted palace, for as the
+torchlight strikes the crystals of salt, they flash and sparkle as if
+the wall was covered with rubies and diamonds.
+
+There is nothing like an enchanted palace in any salt mine of the
+United States, no statues or chapels or chandeliers. There is only a
+hole in the ground, where mining is carried on in much the same manner
+as in other kinds of mines. The shaft is sunk and lined with timbers
+to keep the dirt from falling in, just as in other mines. In working
+salt mines, however, water is almost as bad as earth, and therefore a
+layer of clay is put between the timbers and the earth. There are the
+usual galleries and pillars, with roof and floor of salt. The workmen
+try to get the salt out in lumps or blocks as far as possible, and so
+they bore in drill holes and then blast with dynamite or powder. The
+salt is loaded upon little cars, running on tracks, and is carried up
+the shaft and to the top of a breaker, usually more than one hundred
+feet above the surface of the ground. There it is dumped upon a screen
+of iron bars, which lets the fine salt fall through. The large lumps
+are sold without crushing or sifting, and are used for cattle and
+sheep.
+
+One of the great deposits of salt is in southeastern California. It is
+thought that the Gulf of California used to run much farther north
+than it now does, and that the earth rose, shutting away part of it
+from the ocean. This imprisoned water was full of salt. In time it
+dried, and the sand blew over it till it was far underground. A better
+way than digging was found to work it, as will be seen later; but
+while digging was going on, the workmen built a cottage of blocks of
+salt, clear and glassy. The little rain that falls there melted the
+blocks only enough to unite them firmly together; and there the house
+has stood for many years.
+
+Countries that have no deposits of rock salt can easily get plenty of
+salt from the water of the ocean if they only have a seacoast. About
+one thirtieth of the ocean water is salt, and if the water is
+evaporated, the salt can be collected without difficulty. France makes
+a great deal of salt in this way. When a man goes into the
+manufacture, or rather, the collecting of salt, he first of all buys
+or rents a piece of land,--perhaps several acres of it,--that lies
+just above high water, and makes it as level as possible. Unless it is
+very firm land, he covers it with clay, so that the water will not
+soak through it. Then he divides it into large square basins, making
+each a little lower than the one before it. Close beside the highest
+basin he makes a reservoir which at high tide receives water from the
+ocean. This flows slowly from the reservoir through one basin after
+another, becoming more and more salt as the water evaporates. At
+length the water is gone, and the salt remains. The workmen take
+wooden scrapers and push the salt toward the walls of the basins and
+then shovel it up on the dikes and heap it into creamy cones that
+sparkle in the sunshine. The dikes are narrow, raised pathways beside
+the basins and between them. As you walk along on top of them, you can
+smell a faint violet perfume from the salt. Thatch is put over the
+cones to protect them from the rain, and there they stand till some of
+the impurities drain away. This salt is not perfectly white, because
+the workmen cannot help scraping up a little of the gray or reddish
+clay with it. Most of it is sold as it is, nevertheless, for many
+people have an absurd notion that the darker it is the purer it is.
+For those who wish to buy white salt it is sent to a refinery to be
+washed with pure water, then boiled down and dried.
+
+So it is that the sun helps to manufacture salt. In some of the colder
+countries, frost does the same work, but in a very different manner.
+When salt water freezes, the _water_ freezes, but the salt does not,
+and a piece of salt water ice is almost as pure as that made of fresh
+water. Of course, after part of the water in a basin of salt water has
+been frozen out, what is left is more salt than it was at first, and
+after the freezing has been repeated several times, only a little
+water remains, and evaporation will soon carry this away, leaving only
+salt in the basin, waiting to be purified.
+
+Not very many years ago one of the encyclopaedias remarked that "the
+deposits of salt in the United States are unimportant." This was true
+as far as the working of them was concerned, but in 1913 the United
+States produced more than 34,000,000 barrels. Part of this was made by
+evaporation of the waters of salt springs, and a small share from
+Great Salt Lake in Utah. The early settlers in Utah used to gather
+salt from the shallow bays or lagoons where the water evaporated
+during the summer; but now dams of earth hold back the water in a
+reservoir. In the spring the pumps are put to work and the reservoir
+is soon filled with water. This is left to stand and give the
+impurities a chance to settle to the bottom. Then it is allowed to
+flow into smaller basins, while more water is pumped into the
+reservoir. When autumn comes, the crop of salt is ready to be
+harvested. It is in the form of a crust three to six inches thick,
+some of it in large crystals, and some fine-grained. This crust is
+broken by ploughs, and the salt is heaped up into great cones and left
+for the rain to wash clean. Then it goes to the mill for purifying.
+The water of Great Salt Lake is much more salty than that of the
+ocean. It preserves timber remarkably well, and often salt from the
+lake is put around telephone poles, seventy-five pounds being dropped
+into the hole for each one. It has been suggested to soak timber in
+the Lake, and then paint it with creosote to keep the wet out and the
+salt in.
+
+Salt is also made from the waters of salt springs, which the Indians
+thought were the homes of evil spirits. At Salton, in California, an
+area of more than one thousand acres, which lies two hundred and
+sixty-four feet below sea level, is flooded with water from salt
+springs. When this water has evaporated, all these acres are covered
+with salt ten to twenty inches thick, and as dazzlingly white as if it
+was snow. This great field is ploughed up with a massive four-wheeled
+implement called a "salt-plough." It is run by steam and needs two men
+to manage it. The heavy steel ploughshare breaks up the salt crust,
+making broad, shallow furrows and throwing the salt in ridges on both
+sides. The plough has hardly moved on before the crust begins to form
+again. This broken crust is worked in water by men with hoes in order
+to remove the bits of earth that stick to it, then piled up into cones
+to drain, loaded upon flat trucks, and carried to the breaker. The
+salt fields are wonderfully beautiful in the moonlight, but not very
+agreeable to work in, for the mercury often reaches 140 deg. F., and the
+air is so full of particles of salt that the workers feel an intense
+thirst, which the warm, brackish water does not satisfy. The work is
+done by Indians and Japanese, for white people cannot endure the heat.
+
+A large portion of the salt used in the United States comes directly
+from rock salt strata, hundreds of feet below the surface of the
+ground. These were perhaps the bed of the ocean ages and ages ago.
+There is a great extent of the beds in New York, Michigan, Ohio,
+Kansas, and other States. In Michigan there is a stratum of rock salt
+thirty to two hundred and fifty feet thick and some fifteen hundred to
+two thousand feet below the surface. To mine this would be a difficult
+and expensive undertaking, and a far better way has been discovered.
+First, a pipe is forced down through the surface dirt, the limestone,
+and the shale to the salt stratum. The drill works inside this pipe
+and bores a hole for a six-inch pipe directly into the salt. A
+three-inch pipe is let down inside of the six-inch pipe, and water is
+forced down through the smaller pipe. It dissolves the salt, becomes
+brine, and rises through the space between the two pipes. It is
+carried through troughs to some great tanks, and from these it flows
+into "grain-settlers," then into the "grainers" proper, where the
+grains of salt settle. At the bottom of the grainers are steam pipes,
+and these make the brine so hot that before long little crystals of
+salt are seen floating on the surface of the water. Crystals form much
+better if the water is perfectly smooth, and to bring this about a
+very little oil is poured into the grainer. It spreads over the
+surface in the thinnest film that can be imagined. The water
+evaporates, and the tiny crystals grow, one joining to another as they
+do in rock candy. When they become larger, they drop to the bottom of
+the grainer. They are now swept along in a trough to a "pocket,"
+carried up by an endless chain of buckets, and then wheeled away to
+the packinghouse.
+
+The finest salt is made by using vacuum pans. These are great cans out
+of which the air is pumped, and into which the brine flows. This
+brine, heated by steam pipes, begins to boil, and as the steam from it
+rises, it has to pass through a pipe at the top and is thus carried
+into a small tank into which cold water is flowing. The cold makes the
+steam condense into water, which runs off. The condensed water
+occupies less space than the steam and so maintains the vacuum in the
+pan. For a perfect vacuum the brine is boiled at less than 100 deg. F.,
+while in an open pan or grainer it requires 226 deg. to boil brine. The
+brine is soon so rich in salt that tiny crystals begin to form. These
+are taken out and dried. If you look at some grains of table salt
+through a magnifying glass, you can see that each grain is a tiny
+cubical crystal. Sometimes two or three are united, and often the
+corners are rounded off and worn, but they show plainly that they are
+little cubes.
+
+Most of the salt used on our tables is made by the vacuum process or
+by an improved method which produces tiny flakes of salt similar to
+snowflakes. The salt brine is heated to a high temperature and
+filtered. In the filters the impurities are taken out, and this
+process gives us very pure salt. The tiny flakes dissolve more easily
+than the cubes of salt, and thus flavor food more readily.
+
+With a few savage tribes salt is regarded as a great luxury, but with
+most peoples it is looked upon as a necessity. Some of the early races
+thought a salt spring was a special gift of the gods, and in their
+sacrifices they always used salt. In later times to sit "above the
+salt," between the great ornamental salt cellar and the master of the
+house, was a mark of honor. Less distinguished guests were seated
+"below the salt." To "eat a man's salt" and then be unfaithful to him
+has always been looked upon as a shameful act; and with some of the
+savages, so long as a stranger "ate his salt,"--that is, was a guest
+in the house of any one of them,--he was safe. To "eat salt together"
+is an expression of friendliness. Cakes of salt have been used as
+money in various parts of Africa and Asia. "Attic salt" means wit,
+because the Athenians, who lived in Attica, were famous for their
+keen, delicate wit. To take a story or a statement "with a grain of
+salt" means not to accept it entirely, but only to believe it
+partially. When Christ told his disciples that they were "the salt of
+the earth," he meant that their lives and teaching would influence
+others just as salt affects every article of food and changes its
+flavor. Our word "salary" comes from the Latin word _sal_, meaning
+salt; and _salarium_, or "salt-money," was money given for paying
+one's expenses on a journey. Living without salt would be a difficult
+matter. Cattle that have been shut away from it for a while are almost
+wild to get it. Farmers living among the mountains sometimes drive
+their cattle to a mountain pasture to remain there through the summer,
+and every little while they go up to salt the animals. The cattle know
+the call and know that it means salt; and I have seen them come
+rushing down the mountain-side and through the woods, over fallen
+trees, through briers, and down slippery rocks, bellowing as they
+came, and plunging head first in a wild frenzy to get to the pieces of
+rock salt that were waiting for them.
+
+       *       *       *       *       *
+
+
+
+
+FIRST YEAR IN NUMBER
+
+35 cents net. Postpaid
+
+An Introductory Book to Precede any Series of Arithmetics
+
+BY
+
+FRANKLIN S. HOYT
+
+_Formerly Assistant Superintendent of Schools, Indianapolis_
+
+AND
+
+HARRIET E. PEET
+
+_Instructor in Methods of Teaching Arithmetic, State Normal School,
+Salem, Massachusetts_
+
+The work is based upon the familiar experiences and activities of
+children, and follows as closely as possible the child's own method of
+acquiring new knowledge and skill.
+
+Thus we have lessons based on playing store, making tickets, mailing
+letters, fishing, etc. Every step is made interesting, but no time is
+wasted in mere entertainment.
+
+       *       *       *       *       *
+
+_By the same authors_
+
+THE EVERYDAY ARITHMETICS
+
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+Transcriber's Notes
+
+The List of Illustrations was added, and some of the illustrations
+have been moved from their original positions to avoid breaking up
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