Part 53

Salt is found in large quantities in the sea water, in which it is dissolved with some other substances. It is also found in salt beds, formed by the drying up of old lakes that have no outlets; salt wells, that yield strong brine; and salt mines, in which it is found in hard, solid, transparent crystals, called rock salt. Rock salt is the purest form in which salt is found and, to prepare it for market, it is merely necessary to grind it or cut into blocks. The greatest deposit of salt in the world is probably that at Wielizka in Poland, where there is a bed 500 miles long, 20 miles wide, and 1,200 feet thick. Some of the mines there are so extensive that it is said some of the miners spend all their lives in them, never coming to the surface of the earth.

A trip through these mines is interesting. In one of them can be seen a church made entirely of salt. The salt supply of the United States is obtained chiefly from the salt wells of Michigan and New York, the Great Salt Lake in Utah, and the rock-salt mines of Louisiana and Kansas.

In the arts and manufactures, the most important uses of salt are in glazing earthenware, in extracting metals from their ores, in preserving meats and hides, in fertilizing arid soil, and also, as we shall presently see, in the manufacture of soda. Of equal importance, perhaps, is its use in food. Most people think it not only lends a pleasant flavor, but is itself an important article of diet. It is certain, that all people who can obtain it use salt in their food, and where it is scarce, it is considered one of the greatest of luxuries.

Soda is of interest to us, not so much on account of its use in our households, as because it plays on extremely important part in two industries that contribute greatly to our comfort, viz., the manufacture of glass and soap.

Soda is not found naturally in great abundance, as salt is, but is generally made from other substances. Formerly it was made almost entirely from the ashes of certain plants. One, known as the Salsoda soda-plant, was formerly cultivated in Spain for the soda contained in it, and the ashes, or Barilla, as they were called, were soaked in water to dissolve out the soda. Now, however, the world’s soda supply is produced from common salt by two processes, known from the names of their inventors as the Leblanc and Solvay processes.

~WHERE WE GET SODA~

In the Leblanc process the first step is to treat the salt, or sodium chloride, with sulphuric acid. As a result of this, a compound of sodium, sulphur, and oxygen, called sodium sulphate is formed, together with another acid containing hydrogen and chlorine, and called hydrochloric acid. This acid is driven off by boiling, and the sodium sulphate is left.

The next step in the process is to convert the sodium sulphate, or “salt cake,” into soda, or, to give it its chemical name, sodium carbonate. This change is brought about by mixing the salt cake with limestone and coal and heating the mixture. Just what changes go on when this is done, are not known, but the chief ones are probably the following: the coal, which consists for the most part of an element called carbon, takes the oxygen out of the sodium sulphate, and unites with it to form carbonic acid gas, leaving a compound of sodium and sulphur called sodium sulphide; this acts on the limestone, which is composed of a metal, calcium, in combination with carbon and oxygen, and causes the sulphur in the sodium sulphide to combine with the calcium, forming calcium sulphide, while the sodium combines with the carbon and oxygen and forms the desired compound, sodium carbonate. After the heating, the resulting mass which contains calcium sulphide, sodium carbonate, and some unburned coal, and is known as “black ash,” is broken up and treated with water. This dissolves the sodium carbonate, leaving the rest undissolved, and when part of the water is evaporated crystals containing sodium carbonate and water are formed. By heating these the water may be driven off, and the sodium carbonate left behind as a white powder.

The Solvay, or ammonia soda, process consists in forcing carbonic acid gas through strong brine, to which a considerable quantity of ammonia has been added. When this is done, crystals are formed in the brine, which are composed of a compound of hydrogen, sodium, carbon, and oxygen, and are called sodium bicarbonate. This substance, which is the soda we sometimes use in baking bread, is decomposed by heating, into water and sodium carbonate, the soda used for washing.

The Leblanc process was formerly used almost altogether for making soda; but in recent years the Solvay process has come into extensive use, and it is said that now more than half the soda of the world is made in this way.

Where Do All the Little Round Stones Come From?

The little round stones you are thinking of are really pebbles which have been worn smooth and round by being rubbed against each other in the water, through the action of the waves on a beach, or the running water of brooks and streams. This sort of rock is called a water-formed rock. Some of them have travelled many miles before they are found side by side on the shore or in a large mass of what we would call conglomerate rock. But whenever you see a round smooth rock or pebble you may be quite sure that it was made round and smooth by the action of water.

You sometimes see large rocks made of small stones of various colors and sizes. You can often find a large rock of this kind standing by itself. If you examine it carefully, you will find it consists of an immense number of small stones of different sizes and of a variety of colors, all fastened together as though with cement. This kind of rock is called conglomerate. We know two kinds of conglomerate rock, one, quite common, in which the little stones are round and smooth, and another, not seen so often, in which the stones are sharp. The latter sort is sometimes called breccia, to distinguish it from the former, which is called true pudding stone.

What Is Clay?

Clay is the result of the crumbling of a certain kind of rocks called feldspars. When feldspar is exposed to the action of the weather, it crumbles slowly at the surface and the little fragments combine with a certain amount of water, forming clay. Pure clay is white and is used in the manufacture of china and porcelain. The common clay that we usually think of when we think of clay, is generally yellowish, but there are many different colored clays. Most of these colors,

## particularly those of red clay, yellow clay and blue clay, come from

the iron which is present in the clay. Clay which contains iron is useful for making bricks. Bricks are made from clay by first softening the clay and pressing it in molds, the size of a brick. When dried for a time in the sun they are put into an oven and baked in great heat and they become quite hard and generally red. Most of the clay from which bricks are made turns red when baked, whether blue, yellow or red, because the iron which is in the clay is generally turned red when subjected to heat.

For making porcelains it is desirable to use the kinds of clay which contain nothing that melts when heated to a high degree. Clays which contain substances which melt in strong heat are, therefore, not good for making porcelains. There is a pure white clay called Kaolin which is very excellent for this purpose. Clay out of which we make firebrick for lining stoves and fireplaces is free from substances which melt. Several kinds of clay are good for making paints.

Where Do School Slates Come From?

Slates such as are used in school and as roofing material are formed of clay, which has been hardened under pressure and heat. When this occurs it does so because a number of layers of clay, one on top of the other, have at sometime been subjected to great heat and pressure within the earth with the result that the clay is pressed into very thick layers and changed in color by the heat and becomes hard. There are many kinds of slate. Some of the slate, as found in slate mines, is used to make roofs over buildings and for this purpose they are cut to shapes very much like wooden shingles. They are easily broken, however, as slate is very brittle.

Slate is used in many other ways besides for roofs and school slates. Sometimes it is made into slate pencils but, since paper has become so cheap, comparatively few slate pencils are used in the school room today.

What Causes Shadows?

Where anything through which rays of light cannot pass intercepts the light rays coming from a luminous body, the light rays are turned back in the direction from which they come and the part on the other side of the object which intercepted the light goes into shade and a shadow results. A shadow then is produced by cutting off one or more light rays. We notice shadows when the sun is bright in the daytime and at night when we walk along the streets lighted partly by street lamps. The shadows we see in the daytime are caused by our cutting off and throwing back some of the light rays which come from the sun. These are not so dark as the shadows we see at night because the rays of light from the sun are so bright and are reflected from so many other objects to the side and in back of us.

When, however, we are walking along a dimly lighted street and come to a street lamp the shadows our bodies cause are quite black. The night shadows are darker because the source of light is less intense and the objects to the side of and in back of us (if we are walking toward the light) do not reflect so much of the light rays as they do of the sun’s rays in the daytime.

[Illustration: DRIVING THE HOLLOW STEEL PILES TO BED ROCK.]

The Foundation of a Sky Scraper

How Hollow Steel Piles, Compressed and Concrete Are Employed to Make a Foundation

Rapidity of building construction is of primary importance in every city of metropolitan size. When real estate is sold at the rate of several hundred dollars a square foot it is self-evident that time is indeed money. The delay of a few days in completing a structure may deprive the owner of the chance of earning thousands in rental money. Because of the excessive depth of an open caisson, the completion of a foundation may be delayed for months. Hence the building may not be completed until the renting period has passed and the owner must wait an entire year before he can expect any financial return on his investment.

Because rapidity is so essential in city building construction the method of first sinking an open pit to rock in providing a foundation has been displaced to a large extent by a system in which heavy hollow steel piles are employed in clusters to support a building. The hollow piles are driven through quicksand to rock, cleaned out and ultimately filled with concrete.

~PILES ARE DRIVEN DOWN TO SOLID ROCK~

In this method of constructing foundations, which is illustrated, hollow steel piles are driven in the well-known manner down to solid rock. The steel pile sections vary in length from 20 feet to 22 feet, and in diameter from 12 inches to 24 inches. If the ground is to be penetrated to a depth greater than 22 feet, the sections of piling are connected by means of a sleeve in such manner that a watertight joint is formed. Under a pressure of 150 pounds to the square inch a jet of compressed air is then employed to blow out the earth and water contained within the shell. A spouting geyser of mud rising sometimes to a height of 150 feet, and occasional large pieces of rock blown up from a depth of 40 feet below the ground, bear testimony to the terrific force of the air blast.

[Illustration: THE PILES ARE ABOUT TWENTY-TWO FEET LONG. IF GREAT DEPTHS ARE TO BE REACHED SECTIONS OF PILING ARE JOINED TOGETHER BY MEANS OF A SLEEVE.]

When the shell has been completely cleaned out by means of the blast of compressed air, the exposed rock can be examined by lowering an electric light. Steel sounding rods are employed to test the hardness of the rock and to detect the difference between soft and hard bed rock. After the piles in each pier have been cleaned out, they must be cut off at absolutely the same height--sometimes a very difficult task when there is little room. The oxy-acetylene torch is used for the purpose, the intensely hot flame cutting off the steel almost like butter at the exact elevation desired.

[Illustration: CUTTING STEEL PILES WITH A HOT FLAME

PILE BEING CUT TO PROPER LEVEL BY MEANS OF OXY-ACETYLENE TORCH.

After the piles in each pier have been cleaned out they must be cut off at exactly the same height--sometimes a very difficult task when there is little room. The oxy-acetylene torch is used for the purpose, the intensely hot flame cutting off the steel almost like butter.]

[Illustration: A CLUSTER OF PILES, CLEANED OUT, FILLED WITH CONCRETE AND CUT OFF FLUSH BY MEANS OF THE OXY-ACETYLENE FLAME.]

~PILES ARE NEXT FILLED WITH CONCRETE~

The hollow shell is next filled with concrete reinforced by means of long two-inch steel rods, sometimes fifty feet in length. On clusters of these concrete-filled piles, the weight of the building is supported.

That this method of constructing foundations is indeed rapid, the story of the work at 145-147 West Twenty-eighth Street, New York City, proves. Rock was located 38 feet below the curb. The material above it was clay and water-bearing sand. Structural steel was due in three weeks, but the completion of the cellar was still ten days off. The steel pile foundation method offered the only solution of the problem. Specifications were drawn which called for eighty-five 12-inch steel piles, driven to rock, blown clean by compressed air, and filled with concrete, reinforced with 2-inch rods. Despite various obstructions on the ground (shoring of neighboring buildings and the like) the driving was started on June 30th. The excavator was still taking out his runway while the rear half of the lot was completely driven. After he had left the ground a compressor was set up, and the first pipe was blown on July 7th. Three days later all driving and cleaning had been completed. During the following two days all the piles were filled and capped. In a word, the entire foundation had been completed three days before the expected arrival of the steel.

[Illustration: CONCRETE PILES WHICH HAVE BEEN SUNK TO ROCK BOTTOM AND IN WHICH TWO-INCH STEEL RODS HAVE BEEN INSERTED TO ACT AS REINFORCEMENT FOR THE CONCRETE WHICH WILL EVENTUALLY BE POURED IN.]

Such rapid work is not unusual with the steel foundation method. On another contract, work was completed not in the three months stipulated, but in exactly one month and a half, during which brief time all the excavation had been done, including sheeting, shoring, pile-driving, the mounting of concrete girders to carry the wall and capping of the piles ready to receive the grillage.

[Illustration: THE STEEL PILE IS EASILY FORCED EVEN THROUGH THE SOFT UPPER LAYERS OF BED ROCK. SOMETIMES VERY LARGE PIECES ARE BLOWN UP INTO THE AIR BY THE BLAST OF COMPRESSED AIR.]

Sometimes difficulties are encountered which would prove all but insurmountable and certainly hopelessly expensive with other methods. Thus in carrying out the one contract, water was found 12 feet from the curb. Two running streams had intersected at that point. The piles were simply sunk through the stream to rock bottom without any difficulty.

The excessive cost of open-pit work has sometimes made it impossible to build twelve or fourteen-story buildings in many sections of the city of New York. The steel pile has, however, made steel building construction profitable.

The carrying capacity of a steel pile is enormous. On a single 12-inch steel pile one hundred tons can be safely maintained. Piers containing sixteen piles have been used, and loadings up to 1300 tons are not unusual.

Naturally the question arises: Do the steel piles deteriorate in time? The question has been answered over and over again by the piles themselves. After a service of fifteen years the steel foundation piles were removed from the site of a building which now stands at the northwest corner of Wall and Nassau streets, in New York City. They showed practically no deterioration. The oxidation on the outside was almost negligible.

[Illustration: BLOWING OUT MUD AND ROCK WITH COMPRESSED AIR

CLEANING OUT A HOLLOW STEEL PILE BY MEANS OF COMPRESSED AIR A GEYSER OF MUD ALWAYS APPEARS.]

[Illustration: A DRIVEWAY ALONG THE TOP OF THE OLIVE BRIDGE DAM.]

The Story in a Glass of Water

How Does the Water Get into the Faucet?

It is easy for you boys and girls who live in the city to run into the kitchen or bathroom when you are thirsty and by a simple turn of the faucet tap secure a glass of cool and refreshing water, but did you ever stop to think how many men must constantly work and how great and perfect arrangements must be made before it is possible to supply a great city with water to drink, to bathe in, and for cooking and washing?

No one who has never had the experience of being in a town or city from which the water supply has been cut off, for a day or a number of days, can realize how necessary water is in our daily lives. We are so used to having all the water we want at any time that we even complain when in summer we are asked to drink water which is not iced. Drinking ice-water is very much of a habit. In tropical countries where there is no ice, people drink the water just as they find it, and if you were to go there and drink the waters for a few days, you would soon find that the water slakes your thirst even when quite warm, so it is not the ice in the water that quenches your thirst, but the water itself, and the ice-water is not good for you, as the doctor will tell you, because it chills the stomach.

Where Does Our Drinking Water Come from?

The best way to find out where the water in the faucet comes from is to follow it back to its source. Let us see. Here we are in the kitchen and you have just had a drink of water taken from the faucet above the sink. The faucet, you will notice, is attached to a small pipe which is fastened to the wall back of the sink. We look under the sink and see that the pipe goes through a hole in the floor, so we reason that the water must come from the cellar. Let us go down cellar and see. Yes, here is the little pipe that comes down through the floor under the sink and we follow it along the wall toward the front of the house, and well, well, there it goes right out through the stone foundation of the house. So we conclude that the water comes from somewhere outside of the house, and that the little pipe we have been following is only a means of getting it from the outside into the house. We now mark the place in the wall where the pipe goes through and run around to the front of the house to see where it comes out, but we don’t see it. It must be buried in the ground, so we get a spade and pick and begin to dig a hole in the ground, and pretty soon we find the little pipe pointing straight out toward the street. We keep on digging the dirt away, and thus open a little trench from the house to the middle of the street and when we get there after a great deal of digging we find our little pipe attached to a larger pipe which seems to run along the ground in the middle of the street; so we are still in the dark as to where the water comes from, excepting that so far as our own home is concerned we know that it gets into the house through a little pipe which is attached to a big pipe in the middle of the street. By this time we know we have a big job on hand.

[Illustration: HOW A BIG DAM IS BUILT

BUILDING OLIVE BRIDGE DAM TO FORM THE ASHOKAN RESERVOIR.

The great Ashokan reservoir is situated about fourteen miles west of Kingston on the Hudson River. Its cost is $18,000,000, and it will hold sufficient water to cover the whole of Manhattan Island to a depth of twenty-eight feet. The water is impounded by the Olive Bridge dam, which is built across Esopus Creek, and also by the Beaver Kill and the Hurley dikes, which have been built across streams and gaps lying between the hills which surround the reservoir.]

[Illustration: THE OLIVE BRIDGE DAM, 4650 FEET LONG, 200 FEET HIGH.

The dam is a masonry structure 190 feet in thickness at the base, and 23 feet thick at the top. The surface of the water when the reservoir is full is 590 feet above tide level. The total length of the main dam is 4560 feet, and the maximum depth of the water is 190 feet. The area of the water surface is 12.8 square miles, and in preparing the bottom it was necessary to remove seven villages, with a total population of 2000. Forty miles of highway and ten bridges had to be built. In the construction of the dam and dikes it was necessary to excavate nearly 3,000,000 cubic yards of material, and 8,000,000 cubic yards of embankment and nearly 1,000,000 cubic yards of masonry had to be put in place. The maximum number of men employed on the job was 3000.]

~HOW THE PIPES RUN THROUGH THE STREET~

We are pretty tired of digging by this time, so we call in all the boys and girls in town to help us dig so that we may see where these pipes come from, and we have a regular digging carnival. We follow the big pipe along our own street until we come to the corner. Here we find that our larger street pipe is connected with a still larger pipe, so we think we had better follow the larger pipe. We keep on digging, getting more of the boys and girls to help, and we follow that big pipe right out to the edge of town where we see it runs into another stone wall which you knew all the time was the reservoir, but concerning what it was for you were perhaps never quite clear.