Fig. 96FIG. 96.—A PROSPECTOR IN THE DESERT
The prospector needs little capital except health and strength, but he must be willing to lead a rough life. He will be more likely to succeed if he knows something about the different kinds of minerals and rocks, and is able to distinguish the valuable ones from those which are of little or no worth.
The prospector may have a pack-horse and a second horse to ride, or he may go afoot with merely two burros to carry blankets, provisions, and tools. A burro costs little and will live upon almost anything. The variety of food that can be carried is not large; such things as bacon, flour, sugar, beans, and coffee are the most important. With the rifle one may frequently add to the supply. This, you may think, is pretty hard fare, but life in the open air will make one hungry enough to relish almost any sort of food.
The prospector does not need a road or even a trail. He seeks the least-known portion of some mountain district where he has an idea that gold may be found. Through the cañons he goes, and over the mountains, either on horseback or driving the burros before him. Water and grass are usually abundant, and the little cavalcade stops where night overtakes it. In the desert prospecting is more difficult and often dangerous, because of the scarcity of water. It is necessary to know the location of the few scattered springs, and to make one of the burros useful in carrying water kegs. A spring must be the starting-point in the morning, and a sufficient amount of water must be taken to last until the traveller can get back to the same spring or until he can reach another.
A pick, a shovel, and a hammer are among the most important parts of the prospector's outfit. Gold is a heavy substance, and as it washes down the mountain sides and into the gulches from some quartz vein, its weight finally takes it to the bed-rock beneath the sand and gravel. With his pick and shovel the prospector can reach the bed-rock. He takes some of the gravel from its hiding-place close to the rock, places it in a pan filled with water, and then, with a peculiar rotary movement, washes away the lighter materials, leaving the heavier substances and the gold, if there is any, at the bottom of the pan. If there is no trace of gold, the prospector goes on to another creek; but if some of the yellow metal is washed out, he tests the place thoroughly for more.
In searching for ledges the prospector spends his time in the smaller gulches and upon the mountain sides. Every piece of detached quartz that meets his eye is examined, and if any specks of gold appear, the search is directed toward the vein or ledge from which the specimen came. With the hammer, pieces of quartz are broken from the veins which here and there rise above the surface of loose and crumbling rock. When the worker finds a piece that is stained with iron and has the appearance of carrying gold, he places it in his bag and keeps it for further examination. At camp, the pieces of quartz are pounded to a powder in a mortar and then washed in a horn spoon. A string of fine grains of gold tells of the discovery of a rich vein.
Fig. 97FIG. 97.—A PROSPECTOR'S CABIN IN THE ROCKY MOUNTAINS
It is not usually an easy matter to find home of a piece of stray quartz upon the mountain side. Days and weeks may pass while search is made up the slope, for the fragment must have come from some point above. But the ledge, once discovered, is traced along the surface for the purpose of determining its direction and extent.
When a promising bed of gravel or a vein of gold-bearing quartz is found, the prospector posts the proper notices of his right to the claim and has them recorded at the nearest land office. Then he makes a permanent camp by cutting down trees and building a cabin. The interior of the cabin is very simple. Its table and chairs are made of split lumber. One end of the single room is occupied by the bunk, and the other by a large fireplace. There may be no windows, and the roof may be made of earth piled upon logs, or of long split shingles commonly known as shakes.
Sometimes, after discovering a very rich quartz ledge, the prospector goes back to a settlement to attempt to interest some one in buying or developing it. Sometimes it happens that he loses the location of the vein and cannot go back to the place where it was discovered. In this way his discovery becomes a "lost mine," and grows in importance in people's minds as the story of its riches spreads from one to another. Although men may spend years looking for such mines, they are not often found again.
Frequently two men go prospecting together so that their work will be less dangerous and lonely. If they are not at once successful, they manage in some way to get supplies for a trip each year into the mountains. Often they are "grub-staked," that is, some man who has money furnishes their supplies in return for a share in their findings.
If they have enough to eat, the prospectors, in their snug cabin, are comfortable and happy. The cabin is built as near as possible to the mine, so that the men need not be cut off from their work during the stormy weather. The temperature underground is about the same in both winter and summer, so that winter storms and summer heat form no hindrance to the work.
Fig. 98FIG. 98.—MOUTH OF A TUNNEL
Years spent in life of this kind lead men to love the mountains. They feel a sympathy with Nature and a companionship in her presence. When they have to visit the town for supplies, they long to get back to their little cabins. They feel lost in the whirl and confusion of the city.
Summer is a delightful time at the many little miners' cabins scattered through the mountains. The air is invigorating, the water pure and cold. There is everything in the surroundings to make one happy. In the winter the miner sits by his great fireplace, with the flames roaring up the chimney. He has no stove to make the air close and oppressive. About the fireplace his dishes are arranged—the kettle for beans, the coffee-pot, and the Dutch oven in which the bread is baked. If there are some old paper-covered story-books at hand, it does not matter how fiercely the storms rage without. Ask any old prospector who has spent years in this manner if he would exchange his cabin for a house in the city, and he will most decidedly answer "no."
This lonely life in the mountains seems to engender hospitality. The old-time prospector will make you welcome to his cabin and will share his last crust with you. When he asks you in to have some coffee and beans, he does not do it merely for the sake of being polite, and he will feel hurt if you do not accept his hospitality. His dishes may not be as white as those to which you are accustomed, but I will venture to say that you have never tasted better beans than those with which he will fill your plate from his soot-begrimed kettle.
We ought all to see more of this wildlife. Even if we do not care to, make our permanent homes among the mountains, it would do us good to go there every summer at least, and so not only become stronger, but cultivate that familiarity with and love for outdoor life which our ancestors enjoyed.
Gold derives its value partly from its purchasing power, partly from those properties which make it serviceable in the arts, and partly from its beauty. The high esteem in which gold money is held is as much the result of its comparative rarity as of its physical properties. Among nearly all the nations of the world it has been agreed upon as a standard of exchange. Gold has one disadvantage as a medium of exchange; it is rather too soft to wear well. But this difficulty is overcome by alloying the gold with another mineral of nearly the same color,—copper, for instance.
In order that we may understand better the position which gold occupies in the arts and trades of the world, let us compare it with other metals, and first with platinum. This mineral is far less abundant and has many properties which make it valuable in the arts. Like gold, platinum is malleable and ductile and does not tarnish in the air, but it differs from gold in not being easily fusible, so that it is used in the laboratory for crucibles. The steel-gray color of platinum is, however, so much less attractive than the yellow of gold, that it is not used for ornamental purposes.
An effort was made at one time by Russia, where a comparatively large amount of platinum is found, to coin this metal into money, but its continued use was not found practicable because of its changing price in the markets of the world. If the leading nations would agree upon a fixed value for platinum, it might be used like gold as a medium of exchange.
Silver is brighter and more attractive than platinum, but is of little use in the laboratory. It has been found in recent years to be so much more abundant than gold that its value has decreased greatly as a commercial article. In our country when coined it has, like paper money, been given a value equal to gold.
The diamond has a value far exceeding that of gold, but this value is dependent almost wholly upon its ornamental properties, although the brilliant stone is also useful as an abrasive and cutting agent.
From these facts it is evident that gold, because of its rarity, its physical properties, and its beauty, combines a larger number of desirable characteristics than any other mineral.
Gold can be found in very small quantities nearly everywhere. It is present in all the rocks and also in sea-water. The gold that is distributed in this manner is of no value to us, for it would cost many times as much to obtain it as it is worth. Nature has, however, concentrated it for us in some places. In portions of the world where the crust has been folded and broken there are veins of quartz extending in long, narrow, and irregular sheets through the rocks. This quartz is the home of the gold, and it is usually found in hilly or mountainous regions.
Do not mistake the yellow iron pyrites for gold. Pyrites is brittle, while gold is malleable. You can hammer a little grain of gold into a thin sheet. Do not make the mistake, either, of thinking that the shining yellow scales of mica which you see in the sand in the bottom of a clear stream are gold. These yellow minerals that look like gold have been called "fools' gold" because people have sometimes been utterly deceived by them.
Fig. 99FIG. 99.—A GOLD-SILVER MINESummit of San Juan Range, Colorado
Summit of San Juan Range, Colorado
Upon the Pacific slope minerals are now being deposited in some of the openings of the rocks from which hot springs issue. A study of these springs has led to the opinion that the gold-bearing quartz veins were formed in a similar manner, but at a very remote time in the past.
The milky or glassy quartz, which is so hard that you cannot scratch it with the point of your knife, the little grains of pale yellow iron pyrites, and the grains and threads of gold scattered through the quartz, were at one time in solution in water. This water came from some region far down in the earth, farther than we can ever reach with the deepest shafts, and there, where it is very hot and the pressure is great, the water dissolved the little particles of gold and other minerals from the rocks; and then, gathering them up, bore them along toward the surface, depositing them as solid particles again in the form of veins in the fissures through which the stream was passing.
Fig. 100FIG. 100.—HYDRAULIC MINING ON THE KLAMATH RIVER, CALIFORNIA
As the rocks upon the surface decay and the crumbling material is carried away by running water, the gold, being very heavy, washes down the hillsides and is at last gathered in the gulches. This fact explains why we find gold both in veins and in the gravel of the streams. Getting gold from the veins is called quartz-mining. Washing it from the gravel is called placer-mining; and if the gravel is deep and a powerful stream of water is required, the work is called hydraulic mining.
Fig. 101FIG. 101.—MAY ROCK, A VEIN OF QUARTZ ON THE MOTHER LODE
Everyone has heard of the Mother Lode of California. Every miner wishes that his mine were upon this famous lode, which is made up of a large number of quartz veins extending along the western slope of the Sierra Nevada mountains, and is marked by hundreds of important mines. A line of towns marks the course of the Mother Lode for over a hundred miles. They are almost entirely supported by the gold which the lode supplies.
The gold first discovered in California was placer gold. After the miners had worked over the stream gravels and had secured all that they could in that way, they began to search for the home of the gold. It could not always have been in the creek beds, and the miners were correct in thinking that it must have been washed from some other place. Gold was so frequently found in pieces of loose or float quartz that this fact finally turned their attention to the quartz veins which were numerous upon the mountain slopes. Then came the discovery of the series of great quartz veins now known as the Mother Lode.
Fig. 102FIG. 102.—AN ARASTRA
When the miners first found the quartz flecked with gold, they used the simplest means for separating the two substances. If the quartz was very rich in gold, it was pounded and ground fine in a hand mortar. Then the lighter quartz was washed away and the gold left.
The miners also made use of the Mexican arastra. This is a very crude apparatus, and is employed even now by miners who cannot afford to procure a stamp-mill. To build an arastra, a circular depression ten or twelve feet wide and a foot or more deep is made in the ground. This depression is lined with stone, which forms a hard bottom or floor. Four bars extend outward from an upright post placed in the middle of the floor, and a large flat stone is fastened to the end of each bar by means of a rope. A horse is hitched to one of the bars, which is purposely left longer than the others. The ore is thrown into the arastra, and water is admitted, a little at a time. As the horse is driven around the stones are dragged over the circular depression, crushing the ore and setting free the gold.
Fig. 103FIG. 103.—THE STAMPS IN A QUARTZ-MILL
This way of separating the gold was too slow, and in a short time the stamp-mill was invented. It has grown from a very simple affair into the great mill which crushes hundreds of tons of ore in a day. The iron stamps each weigh nearly half a ton. They are raised by powerful machinery and allowed to drop in succession upon the ore, which is gradually fed under them. The stamps crush the ore to a fine sand more easily and rapidly than could be done by any other method. Water is kept running over the ore, and as fast as it is crushed sufficiently fine for the particles to pass through a wire screen, the water with which they are mixed is allowed to flow over large plates of copper which have been coated with quicksilver. The latter mineral has an attraction for gold, and so catches and holds most of the particles, no matter how small they are.
The compound of gold and quicksilver is a soft white substance known as amalgam, utterly unlike either metal. When the amalgam is subjected to heat, the quicksilver is driven off in the form of a vapor, and the gold is left pure. The quicksilver vapor is condensed in a cool chamber and is used again.
The iron pyrites in the ore contains gold which cannot be separated by the crushing process and a machine called a concentrator has been invented to save this also. After passing over the copper plates the crushed rock and pyrites are washed upon a broad, flat surface, which is moving in such a way that the lighter rock waste is carried away by the water. The pyrites now appears as a dark, heavy sand. This sand is placed in a roasting furnace, where the sulphur is driven off, and the gold and iron are left together. Now the gold is dissolved by means of chlorine gas, with which it unites in a compound called gold chloride. From this compound the metallic gold is easily separated. All this may seem a complicated process, but it is carried through so cheaply that the ore which contains only two or three dollars to the ton can be profitably worked.
Fig. 104FIG. 104.—MINING THE GRAVEL OF AN OLD RIVER-BED
Not all quartz veins carry gold. There are many in which not a single speck of the precious metal can be found. Gold usually prefers the society of quartz to that of other substances, for minerals, like people, seem to have their likes and dislikes. Along the Mother Lode, however, gold is sometimes found in little bunches and "stringers" scattered through slate. In such cases the slate is mined and sent to the mill.
Some miners devote themselves to pocket mining. They trace the little seams in the rock, and where two seams cross they sometimes find what they call a "pocket." This is a mass of nearly pure gold of irregular shape, varying from a few dollars to thousands of dollars in value. This kind of mining is very uncertain in its results, for a man may make hundreds of dollars in one day, and then not find anything more for months.
The western slope of the Sierra Nevada mountains was once covered with the camps of thousands of placer miners. Piles of boulders and gravel are scattered along the creeks where the eager workers took out millions of dollars' worth of gold-dust and nuggets. Now many of the streams and gulches are entirely deserted. But in other places, where the quartz veins outcrop, there are scores of stamp-mills at work, night and day, pounding out the gold. Some of the mines have been sunk more than a half mile into the earth, and the gold is still as abundant as ever.
In some portions of the mountains hydraulic mining is more common than quartz-mining. Years ago many of the rivers occupied different channels from their present ones. The gravels of these old channels in the Sierra Nevada mountains, and in other parts of the West where gold-bearing veins occur, are rich in gold. In these channels the gold is so deeply buried that it cannot usually be obtained by means of pick and shovel. In order that the overlying gravel may be removed as cheaply as possible, water is supplied by means of ditches, often many miles long. From some near-by hill the stream is conducted down to the mine in strong iron pipes. It thus acquires a great force, and when directed against a gravel bank rapidly washes it away. Torrents of water bearing boulders, gravel, and sand, together with the particles of gold, are turned into sluice boxes lined at the bottom with quick-silver. This metal catches the gold and forms an amalgam as it does in the quartz-mills.
There is a city hidden away in a narrow cañon in the extreme southern portion of Arizona which is supported solely by a copper-mine. The cañon lies upon the southern slope of a range of mountains, and from its mouth one can look far off to the south across the desert plains and mountains of Mexico. The city has an elevation of more than a mile above the sea, and the cañon in which it is situated is so narrow and steep-walled that you can almost jump down from one street upon the roofs of the houses along the street below. Stairways, instead of walks, lead up the hillsides from the main street in the bottom of the cañon.
You might well wonder at the position of the city, and think that out of all the waste land in this region a better place might have been selected for its location. But cities grow where people gather, and people do not come to live in the desert unless there is important work to be done there.
A party of prospectors who were searching carefully over the mountains found several mineral veins with green copper stains crossing this cañon and outcropping in the adjacent hills. Claims were staked out and recorded at the nearest land office. Then shafts and tunnels were opened, and the miners became confident from the rich character of the ore that an important copper-mine might be developed.
Supplies were brought across the desert with teams, and cabins were built in the lonely cañon. Then an enterprising man started a store. As the mine was opened farther, its importance was better understood. There was a call for more miners and the town grew larger. The houses clustered about the mine, the centre of all the activities. At last a railroad was built, and the town became a city, with narrow, winding streets occupying the winding cañon, while tier upon tier of houses crept up the sides of the cañon, which formerly had been covered only by growths of cactus and other plants of the desert.
If the mine should close, there would be no inducement to keep people in the locality, and the city would become merely a group of deserted buildings. Water is so scarce that only a small amount is allowed to each family, and it is delivered in barrels instead of by pipes. Provisions of all kinds are very expensive, for they have to be brought a long distance.
The great mine supports the thousands of inhabitants. The varied industries represented there are dependent upon it alone. As long as it pays to mine the copper, the people are as contented as if they were not tucked away in a cañon in a remote corner of the world.
The most interesting things to be seen about the city are the mine and the smelter. In the former the ore is obtained; in the latter the ore goes through various processes until it comes out in the form of shining, metallic copper. The copper ore, we must understand, is not metallic or "native copper," as it is called when found pure, but a combination of copper with other substances which change its appearance entirely.
Fig. 105FIG. 105.—COPPER SMELTER AND CITY OF BISBEE, ARIZONAThe pipe leading up the hill carries away sulphur fumes from the smelter
The pipe leading up the hill carries away sulphur fumes from the smelter
The mine is opened by a shaft, that is, a square hole sunk in the ground. The shaft of this mine is a thousand feet deep, and is being continually extended downward. If we wish to go down into the mine, we must put on some old clothes and get the foreman to act as guide. The cage in which we are to descend stands at the mouth of the shaft, suspended by a steel rope. It looks much like the elevators found in city buildings. At different levels horizontal passages, called drifts, extend to the right and left upon the vein of copper ore. We step out of the car at one of these levels and with lighted candles start to walk through a portion of the mine. There are so many miles of tunnels that it would take us days to go through them all.
Overhead, under our feet, and upon the sides of the drift, lies the vein of copper are, presenting a different appearance at different places. The various ores sparkle in the light and we gather specimens of each. The common are is chalcopyrite, a copper sulphide; that is, it is composed of copper and sulphur. It has a brass-yellow color, but is often stained with beautiful iridescent tints. In places the chalcopyrite has been changed to the delicate green carbonate of copper called malachite. In other places it has given place to the oxide of copper. The little crimson crystals of this mineral give bright metallic reflections.
The deposit of copper ore is apparently inexhaustible, for in places the vein widens so that chambers one hundred feet wide and several hundred feet long and high have been made in taking it out.
In going through the mine we have to be very careful not to step into openings in the floor of the passages, or drop rock fragments into them, for far below miners may be working. The places where the men are taking out the ore are called "stopes," and to reach them we have to crawl and creep through all sorts of winding passages, now through a "manhole," and now down a long ladder which descends into black depths.
From the stopes the ore, as it is blasted out, is shovelled into chutes running down to some drift where there are men with cars. Each car holds about a ton of ore, and after being filled it is pushed along the drift and upon a cage which raises it to the surface.
Fig. 106FIG. 106.—HOMES OF MINERS, BISBEE, ARIZONA
The mine is not wet, for there is so little rain in this region that there are few underground streams. In places, however, it is warm, for when the oxygen of the air reaches the fresh sulphide it begins to oxidize the ore; that is, it begins to burn it, and change it into a different compound, just as fire changes wood or coal. Wherever oxidation is going on, heat is produced.
Fresh air is constantly needed in these workings far underground. A supply is forced down in pipes, and then allowed to flow back to the surface. In this way a thorough circulation is kept up.
Underground one loses all thought of the changes between night and day, for it is always dark there. Consequently we are surprised on coming up from the mine to find that night has settled over the town. Lights are twinkling everywhere, and miners with their pails of luncheon are coming for the night shift.
Another interesting experience now awaits us in the form of a visit to the smelter. Here the bright copper is extracted from the rough-looking ores. How different the two substances appear! They look as if they had scarcely anything in common.
The interior of the smelter seems like a bit of the infernal regions set upon the earth. While watching what goes on, we might imagine that we were far down in the earth, where Vulcan, the fire god, was at work. At night the scene is particularly weird and impressive, for the shadows and general indistinctness make everything appear strange. The glowing furnaces, the showers of sparks, the roar of the blast furnaces, the suffocating fumes of sulphur, and the half-naked figures of the Mexican workmen, passing to and fro with cloths over their mouths, form all together a bewildering scene.
The ore is first pulverized, and then placed in large revolving cylinders, where it is roasted. A fire is started in the cylinder at first, but after the ore becomes so much heated that the sulphur in it begins to burn, no further artificial aid is necessary. Little by little the ore is added in quantities sufficient to keep the fire going. The object of the roasting is to drive off as much sulphur as possible.
After being raked from the roasting furnace, the ore is wheeled in barrows to the huge upright furnaces and is thrown in. Here such materials as limestone and iron are also added to aid in the formation of a perfectly fused or molten mass. These substances are known as fluxes. With the melting of the ore the copper begins to separate from the impurities.
The melted ore, in the form of a glowing liquid, gathers at the bottom of the furnace and runs out into a large kettle-like receptacle. When ore of these vessels is full it is tipped up and the molten copper which has collected at the bottom, because it is heavier than the slag, is allowed to run into another large kettle, supported by chains from a rolling truck above.
Fig. 107FIG. 107.—SHIPPING COPPER MATTE
The slag is dumped into a car and is carried outside, while the huge dish containing the copper and some slag is swung to the opposite side of the building, where its contents are cast into another furnace. A very strong blast of air is forced up through the molten mass in this furnace, and the remaining portion of slag is blown out at the top in a shower of glowing particles.
From the bottom of the furnace the liquid copper is drawn out and allowed to run into moulds where it finally cools. It is then known as copper matte. The copper still contains some impurities, and retains in addition whatever gold and silver may have been present in the ore. Most copper ores carry a small amount of these precious metals.
The heavy bars of copper matte are now ready for shipment to some manufacturing point, where they are refined still further and made into the various copper utensils, copper wire, etc. Copper is valuable for many purposes, as it does not rust easily, is highly malleable and ductile, and is a good conductor of electricity.
In the great copper-mines upon Lake Superior, copper is found in the native state mixed with the rock, and does not have to be smelted; but in most mines the ore must go through a process very like the one described before metallic copper can be obtained.
It does not matter how remote a region may be, how intense the heat or cold, or how desert-like the surrounding country, men will go to it if minerals of value are discovered; and there they will perhaps spend the whole of their lives, mining these substances which are of such importance to the industries of the world.
People are beginning to ask where fuel will be obtained when the coal-beds are exhausted and the petroleum is all pumped out of the earth. The cold winters will not cease to come regularly, and we shall continue to need fires for many purposes. This is a question which need not trouble us. So long as the sun lasts in the sky and the oceans cover so much of the earth, and so long as there are mountains upon the land, there must be streams with rapids and waterfalls. The power of these streams, which has for ages gone to waste, is now being turned into electricity for purposes of light and heat. We may be sure that long before the mines cease to produce coal and the wells to supply petroleum, there will be something better ready to take their places.
But coal and petroleum are still such important commodities that everyone should know something about the way in which they were made. This earth of ours has had a very long history, much of which has been recorded in the rocks beneath our feet, and the record is more accurate than are many human histories which have been preserved in the printed books.
The story of the earth has been divided into different periods, each marked by the predominance of certain kinds of living things. The Carboniferous period has been so named because at that time the climate and features of the earth in many places favored the growth of dense and heavy vegetation. This vegetation accumulated through the long years, so that it formed thick deposits which gradually changed to beds of coal. It would be wrong, however, to think that all the beds of coal were formed at about the same time. Ever since there have been forests and marshes upon the earth there have been opportunities for the forming of coal-beds. Materials are accumulating even now which will in time be transformed to beds of coal.
We must be equally careful to gain correct ideas of the making of petroleum, for many wrong notions are current. While coal has come from the accumulation of plant remains, petroleum has been derived from sea organisms, chiefly animals. If coal and petroleum are found near each other, the occurrence is accidental and does not mean that the two substances are in any way related.
Our earth is very old, and its surface has gone through many transformations; mountains, plains, and portions of the sea floor have changed places with one another. Wherever there have been marshy lowlands, since plants first began to grow luxuriantly upon the earth, it has been possible for beds of coal to be formed. We all know how rankly plants grow where there is plenty of heat and moisture. Many of us have been in swampy forests and have seen the masses of rotting tree trunks, limbs, and leaves. Now, if we should form a picture in our minds of such a swamp slowly sinking until the water of some lake or ocean had flowed over it and killed the plants, and then washed sand and clay upon the buried forest until it was covered deeply in the earth, we should understand how the coal-beds began. Veins of coal that have been opened by the miners frequently show trunks and stumps of trees, as well as impressions of leaves and ferns. Underneath the coal there is usually a bed of clay, while above sand or sandstone is commonly found.
The oldest coal has been changed the most. It is hard and rather difficult to ignite, but when once on fire it gives more heat and burns longer than other coals. This coal, known as anthracite, is not found extensively in the United States outside of Pennsylvania. Coal which is younger and has been less changed by the heat and pressure brought to bear upon it when it was buried deep in the earth, is known as bituminous. This is the kind of coal which is found in the Mississippi and Ohio valleys, in the Rocky Mountains, and upon the Pacific slope. A still younger coal, which is soft and has a brownish color, is called lignite, and is found mostly in the South and West.
Still another sort of fuel, known as peat, is found in swamps where considerable vegetation is now accumulating, or has accumulated in recent times. Peat is a mass of plant stems, roots, and moss, partly decayed and pressed together. In countries where wood is scarce peat is cut out, dried, and used for fuel.
The larger part of the coal in the eastern United States was formed during the Carboniferous period. That part of our country was then low and swampy; but the West, which is now an elevated area of mountains and plateaus, was at that time largely beneath the ocean.
Then, as the surface of the earth continued to change, the ocean retreated from the Rocky Mountain region, and extensive marshy lowlands with lakes of fresh or brackish water came into existence. There were such marshes in the areas that are now covered by New Mexico, Colorado, Wyoming, Dakota, and Montana. Westward for some distance the land was higher, but in the states of Washington, Oregon, and California there were other marshy lowlands covered with heavy vegetation.
We know from what we have seen of the manner in which wood decays, that in the dry, open air it does not accumulate, but is in great part carried away by the wind. It is only in swamps and shallow bodies of water that the decaying wood can gather in beds. From these facts we have a right to draw conclusions as to the former nature of the surface where there are no coal-beds. There are extensive beds of limestone in the western United States which are of the same age as the coal-beds in the east. As such beds of limestone could have formed only in the ocean, their presence throws a good deal of light upon the geography of those distant times.
Upon the Pacific slope the marshes were not so extensive, nor did they last for so long a period, as those in the East. Nature seems to have confined her strongest efforts at coal-making to the country east of the Rocky Mountains. Perhaps she thought that the people of the West would not need coal if she gave them plenty of gold and silver.
In the Appalachian mountains Nature folded the strata and left them in such a position that the coal could be mined easily. In the Mississippi Valley the beds were left flat, almost in their original position, so that shafts had to be sunk to reach the coal. Upon the Pacific slope Nature seems to have had a large amount of trouble in arranging things satisfactorily. She has made and remade the mountains so many times, and folded and broken the crust of the earth so severely where the swamps stood, that now large portions of the coal beds which once existed have crumbled and been washed away by the streams. The scanty supply of coal which now remains is in most places hard to find and difficult to mine.
Fig. 108FIG. 108.—SEAMS OF COAL ENCLOSED IN SANDSTONE, CALIFORNIA
The best coal mined near the Pacific comes from Vancouver Island. Large beds of a younger and poorer coal are found southeast of Puget Sound. There are other beds in the Coast ranges of western Oregon, and a few small ones in the Coast ranges of California. The great interior region between the Rocky Mountains and the Coast ranges has very little coal. The people of California have to import large quantities of coal. Some is brought by the railroads from the Rocky Mountain region, but the most comes by ships from various parts of the world, from England, Australia, or British Columbia. The ships bring the coal at low rates and take away grain and lumber.
Coal is almost the only important mineral which Nature has bestowed sparingly upon the Pacific slope. In California, however, she has made amends by storing up large quantities of petroleum. In Pennsylvania and Ohio there is petroleum as well as coal. Oil has also been discovered in the Rocky Mountain region and in Texas.
Fig. 109FIG. 109.—A SPRING OF WATER AND PETROLEUMThe black streak is petroleum
The black streak is petroleum
Petroleum is found flowing from the rocks in the form of springs, either by itself or associated with gases and strong-smelling mineral water. The oil is usually obtained by boring wells, but in southern California there is one mountain range which furnishes large quantities through tunnels which have been run into its side. Petroleum is commonly found in porous sandstones or shales, from one or two hundred to three thousand feet below the surface. It was not made in these rocks, but has soaked into them just as water soaks into a brick. The rocks which produced the oil or petroleum are dark, strong-smelling shales or limestone. Heat a piece of such rock, and you will drive out a little oil.
Fig. 110FIG. 110.—OIL WELLS IN THE CITY OF LOS ANGELES, CALIFORNIAPool of oil in foreground
Pool of oil in foreground
Examine a piece of the shale from one of the oil districts of California, and you will discover that it is a very peculiar rock, for it is made up almost wholly of minute organisms which once inhabited the ocean. Among the forms which you will find are the silicious skeletons of diatoms, the calcareous skeletons of foraminifera, scales of fish, and, rarely, the whole skeleton of a fish.
Where now there are mountains and valleys dotted with oil derricks, there was once the water of the open ocean. This water was filled, as the water of the ocean is to-day, with an infinite number of living things. As these creatures died, their bodies sank to the bottom, and while the soft parts dissolved, the hard parts or skeletons remained. Through perhaps hundreds of thousands of years, the skeletons continued to accumulate until beds were formed hundreds or even thousands of feet in thickness. The materials of the beds, at first a soft mass like the ooze which the dredger brings up from the bottom of the present ocean, became packed together in a solid mass.
Then disturbances affected this old sea bottom. It was raised, and gravel, clay, and sand from some new shore were washed over the bed of animal remains, burying it deeply. Continued movements of the earth finally folded these rocks, which, as they were, squeezed and broken, became warm. The heat and pressure started chemical action in the decayed animal bodies, and particles of organic matter were driven off in the form of oil and gas. These substances were forced here and there through the fissures in the rocks. Part of the products found a way to the surface and formed springs, while other portions collected to form vast reservoirs in such porous rocks as sandstone. The sulphur and mineral springs which occur in oil regions tell us that this work of oil-making is still going on.
The oil as it comes from the ground is usually brownish or greenish in color, and much thicker than the refined product which we use in our lamps. Some of the crude petroleum is thick and tar-like in appearance, and when long exposed to the air turns to a solid black mass called "asphaltum." This, when softened by heat and mixed with sand, makes a valuable material for street pavement.
The western portion of the United States exhibits very interesting climatic features. In California, for example, there may be found every degree of temperature between tropic heat and arctic cold. In the deserts of the southeastern portion of the state the air is extremely dry, while in the northwest it rains nearly every month in the year.
Upon the borders of Puget Sound the thermometer seldom falls below the freezing-point, while southern Newfoundland, in the same latitude, is marked by cold and snowy weather for at least six months of every year. Southern California has the same latitude as central Georgia, but its average temperature near the coast is but little higher than that of Puget Sound, while it is warmer in winter and cooler in summer than Georgia. The deserts of southern California and Arizona are so hot that for four months of the year work in the sun is almost impossible; yet the higher portions of the Sierra Nevada mountains, but a short distance away, have an arctic climate. The whole Pacific coast region has, with the exception of the mountains, a much milder climate than one would expect from a mere knowledge of its latitude. It will be instructive to search out the reasons for the remarkable contrasts in climate presented by different portions of the slope.
The imaginary lines passing through points of equal temperature upon the earth are called "isotherms." These lines rarely accord in direction with the parallels of latitude, but curve far to the north or south. The irregular course of the isotherms is due to many causes. Among these are the distribution of the land and water, the direction of the prevailing wind, the position of the mountain ranges, and the elevation above sea-level.
In winter the isotherms curve far to the north over the North Pacific and North Atlantic oceans; but over the intervening land they curve as much to the south. In summer the isotherms are almost reversed in position, at least as far as the land is concerned, for they bend to the north in the heart of the continent. There are important reasons for the slight variation of the isothermal lines upon the western borders of North America and Europe, and their great change of position in the interior from winter to summer, but these reasons are not at all difficult to understand.
The temperature of large bodies of water changes but little throughout the year, for water warms and cools slowly. The surface of the land, on the contrary, heats rapidly, and then as quickly loses its heat with the changing season. The air over the ocean is cooler in summer and warmer in winter because of the influence of the water, but over the land, in districts far from a large body of water, the changes in temperature between day and night, summer and winter, are very great.
It was formerly thought that the warm Japan current, which flows against the western shore of North America, was responsible for the exceptionally mild climate there, and that the Gulf Stream produced a similar climate upon the coast of western Europe. More careful study, however, has shown that not the warm ocean currents, but rather the winds blowing from the water, are the cause of the mild climate in those lands across which they blow. In temperate latitudes there is a slow movement of the air in an easterly direction, and in consequence the climate of the western coast of North America is not marked by such extremes in winter and summer as are the interior and the eastern sections. It is also surprising to find how nearly alike the average winter and summer temperature is at San Francisco. It is also surprising to note that the average temperature of Seattle differs so little from that of San Diego, although these two places are separated by sixteen degrees of latitude.
In some places the climatic conditions which we should naturally expect seem to be reversed. Oranges are grown in the Great Valley of California as far north as Red Bluff, and actually ripen a month sooner than they do near Los Angeles, five hundred miles farther south. The early ripening of fruits in the Great Valley may be explained by the presence of the inclosing mountain ranges: the Sierra Nevada mountains upon the northeast shut off the cold winds of winter, while the Coast ranges upon the west break the cool summer winds which come from off the Pacific.
Another interesting fact connected with the climate of the West is the influence exerted by the direction of the mountain ranges. As these ranges usually lie across the path of the prevailing winds, their tempering influence is lost much more quickly than it otherwise would be. West of the Coast ranges the summers are cool and the winters are warm. Upon the eastern side of these mountains the winters are somewhat cooler and the summers very much warmer. In the dry, clear air of the desert valleys, far from the ocean, the daily range in temperature is sometimes as great as fifty degrees, while the winters are cool and the summers unbearably hot.
We all know how much cooler a hill-top is than a valley upon a summer day. Where the mountains rise abruptly to a great height, as, for example, does the San Bernardino Range of southern California, one can stand among stunted plants of an arctic climate and look down upon orange orchards where frost rarely forms. Mount Tamalpais, a peak of the Coast Range north of San Francisco, has an elevation of nearly three thousand feet. The summer temperature upon this mountain forms an exception to the general rule, for while the lowlands are buried in chilling fog, the air upon the summit is warm and pleasant.