Part 21

Millions of dollars’ worth of property has been recovered from the ocean’s depth by divers. One of the greatest achievements in this line was by the famous English diver, Lambert, who recovered vast treasure from the “Alfonso XII,” a Spanish mail steamer belonging to the Lopez Line, which sank off Point Gando, Grand Canary, in 26¹⁄₂ fathoms of water. The salvage party was dispatched by the underwriters in May, 1885, the vessel having £100,000 in specie on board. For nearly six months the operations were persevered in before the divers could reach the treasure-room beneath the three decks. Two divers lost their lives in the vain attempt, the pressure of water being fatal. The diver recovered £90,000 from the wreck, and got £4,500 for doing it.

One of the most difficult operations ever performed by a diver was the recovering of the treasure sunk in the steamship “Malabar,” off Galle. On this occasion the large iron plates, half an inch thick, had to be cut away from the mail-room, and then the diver had to work through nine feet of sand. The whole of the specie on board this vessel--upward of $1,500,000--was saved, as much as $80,000 having been gotten out in one day.

It is an interesting fact that from time to time expeditions have been fitted out, and companies formed, with the sole intention of searching for buried treasure beneath the sea. Again and again have expeditions left New York or San Francisco in the certainty of recovering tons of bullion sunk off the Brazilian coast, or lying undisturbed in the mud of the Rio de la Plata.

At the end of 1885, the large steamer Imbus, belonging to the P. & O. Co., sank off Trincomalee, having on board a very valuable East-India cargo, together with a large amount of specie. This was another case of a fortune found in the sea, for a very large amount of treasure was recovered.

Another wreck from which a large sum of gold coin and bullion was recovered by divers, was that of the French ship “L’Orient.” She is stated to have had on board specie to the value of no less than $3,000,000, besides other treasure.

A parallel case to “L’Orient” is that of the “Lutine,” a warship of thirty-two guns, wrecked off the coast of Holland. This vessel sailed from the Yarmouth Roads with an immense quantity of treasure for the Texel. In the course of the day it came on to blow a heavy gale; the vessel was lost and went to pieces. Salvage operations by divers, during eighteen months, resulted in the recovery of £400,000 in specie.

Humorous scenes do not play much of a part on the ocean’s bottom, and the sublime and awe-inspiring are far more in evidence there than the ludicrous, yet even beneath the waves there are laughable scenes at times. A diver had been engaged to inspect a sunken vessel off the coast of Cuba. Arriving on the scene he discovered a number of native sponge-divers, who descend to considerable depths, diving down from their canoes to the sunken vessel trying to pick up something of value. They paid little attention to the arrival of the wrecking outfit, and did not notice the diver descend, until suddenly what seemed to them to be a horrible human-shaped monster, with an immense head of glistening copper and three big, round, glassy eyes, came walking around the vessel’s bow and made a big salaam to them. That was enough. They shot surfaceward like sky-rockets, climbed frantically into their canoes and hurriedly rowed away.

What Happens When Anything Explodes?

By explosives are meant substances that can be made to give off a large quantity of gas in an exceedingly short time, and the shorter the time required for the production of the gas the greater will be the violence of the explosion. Many substances that ordinarily have no explosive qualities may be made to act as explosives under certain circumstances. Water, for example, has caused very destructive boiler explosions when a quantity of it has been allowed to enter an empty boiler that had become red hot. Particles of dust in the air have occasioned explosions in saw mills, where the air always contains large quantities of dust. A flame introduced into air that is heavily laden with dust may cause a sudden burning of the particles near it, and from these the fire may be conveyed so rapidly to the others that the heat will cause the air to expand suddenly, and this, together with the formation of gases from the burning, will cause an explosion.

It must not be thought, however, that fine sawdust or water would ordinarily be classed as explosives. The term is generally applied only to those substances that may be very easily caused to explode.

The oldest, and most widely known, explosive that we possess is gunpowder, the invention of which is generally credited to the Chinese. It is a mixture of potassium nitrate, or saltpeter, with powdered charcoal and sulphur. The proportions in which these substances are mixed vary in different kinds of powder, but they usually do not differ much from the following:

Sulphur 10 per cent. Charcoal 16 per cent. Saltpeter 74 per cent.

The explosive quality of gunpowder is due to the fact that it will burn with great rapidity without contact with the air, and that in burning it liberates large volumes of gas. When a spark is introduced into it, the carbon, charcoal, and sulphur combine with a portion of the oxygen contained in the saltpeter to form carbonic acid gas and sulphurous acid gas, and at the same time the nitrogen contained in the saltpeter is set free in the gaseous form. This action takes place very suddenly, and the volume of gas set free is so much greater than that of the powder that an explosion follows.

In the manufacture of gunpowder all that is absolutely necessary is to mix the three ingredients thoroughly and in the proper proportions. But to fit the powder for use in firing small arms and cannon it is made into grains of various sizes, the small sizes being used for the small arms with short barrels, and the large sizes for cannon. The reason for this is that if the powder is made in very small grains it all burns at once, and the explosion takes place so suddenly that an exceedingly strong gun is required to withstand the explosion, while if larger grains are employed the burning is slower and continues until the projectile has traveled to the muzzle of the gun. In this way the projectile is fired from the gun with as much force as if the explosion had taken place at once, but there is less strain on the gun.

What Causes the Smoke When a Gun Goes Off?

Powder of this latter kind always produces a considerable quantity of smoke when it is fired, because there is a quantity of fine particles formed from the breaking up of the saltpeter and from some of the charcoal which is not completely burned. This smoke forms a cloud that takes some time to clear away, which is a very objectionable feature. In order to get rid of it, efforts were made to produce a substance that would explode without leaving any solid residue, and that could be used in guns. These efforts were finally successful, and there are now several brands of smokeless powder in use.

What is Smokeless Powder Made Of?

The most satisfactory forms of smokeless powder are all made from guncotton or nitrocellulose. This substance, which is made by treating cotton with a mixture of nitric and sulphuric acids, is a chemical compound, not a mixture like gunpowder; and when it is exploded it is all converted into gases, of which the chief ones are carbonic acid gas, nitrogen, and water-vapor. To cause the explosion of guncotton it is not necessary to burn it, but a mere shock or jar will cause it to decompose with explosive violence. Of course, such a violent explosive as this could not be used either in small arms or in cannon, but guncotton can be converted into less explosive forms which are suitable for use in guns, and the majority, of smokeless powders are made in this way. The methods used in producing the smokeless powders are kept secret by the various countries that use them.

What is Nitroglycerine?

Another very powerful explosive, which is closely related to guncotton, is nitroglycerine. This compound is made by treating glycerine with the same sort of acid mixture that is used in making guncotton. It explodes in the same way that guncotton does and yields the same products. It is an oily liquid of yellow color, and on account of its liquid form it is difficult to handle and use. The difficulty in handling nitroglycerine led to the plan of mixing it with a quantity of very fine sand called infusorial earth. When mixed with this a solid mass called dynamite is formed, which is easier to handle and more difficult to explode, but which has almost as much explosive force as nitroglycerine.

A more powerful explosive than either nitroglycerine or guncotton is obtained by mixing them together. When this is done the guncotton swells up by absorbing the nitroglycerine and becomes a brownish, jelly-like substance that is known as blasting gelatin. This is generally considered the most powerful explosive obtainable.

What Makes Nitroglycerine and Guncotton Explode So Readily?

Let us now consider for the moment what it is that makes guncotton, nitroglycerine, and blasting gelatin explode so readily. The explanation is found in the presence in them of nitrogen. As you remember from what you learned about air, nitrogen is an extremely inactive element. It has no strong tendency to combine with other elements, and when it does enter into combination with them the compounds formed are almost always easily decomposed. In the compounds that have just been described a shock causes a loosening of the bonds that hold the nitrogen, and the whole compound goes to pieces just as an arch falls when the keystone is removed.

What Is Silver?

Since the earliest time recorded in history, silver has been the most used of the precious metals, both in the arts and as a medium of exchange. Even in the prehistoric times silver mines were worked and the metal was employed in the ornamental and useful arts. It was not so early used as money, and when it began to be adopted for this purpose, it was made into bars or rings and sold by weight. The first regular coinage of either gold or silver was in Phrygia, or Lydia, in Asia Minor. Silver was used in the arts by the Athenians, the Phœnicians, the Vikings, the Aztecs, the Peruvians, and in fact by all the civilized and semi-civilized nations of antiquity. It is found in almost every part of the globe, usually in combination with other metals. The mines in South America, Mexico, and the United States are especially rich. Silver is sometimes found in huge nuggets. A mass weighing 800 pounds was found in Peru, and it is claimed that one of 2,700 pounds was extracted in Mexico. The ratio of the value of silver and gold has varied greatly. At the Christian era it was 9 to 1; 500 A.D. it was 18 to 1; but in 1100 A.D. it was only 8 to 1. In 1893 it was as high as 2,577 to 1. The subject has entered largely into American politics as a disturbing element, and in 1896 the Democratic party, in its national convention, declared for the free coinage of the metals at 16 to 1. The Republican party adhered to the gold standard and declared against the free coinage of silver. Each party reaffirmed in 1900 this plank in its platform. In both years the Democrats were defeated.

What Is Worry?

Worry is a feeling of fear, but is never of the present. It is always about something that may happen or that has happened. It is generally in the future, sometimes in the past, but never in the present.

An animal that knows neither future nor past cannot worry. Babies, living only as they do in the present, cannot worry. All creatures, excepting human beings, live only in the present and therefore they do not worry, for such creatures cannot remember what happened in the past or guess what is going to happen.

A human being after arriving at a certain age is given such powers that his mind can go back to the past and cast itself forward into the future as he thinks it will be, because he has imagination. As a matter of fact we live less in the present than in the past or future.

Why Do We Worry?

We worry because we are able through a power called self-consciousness to place ourselves through our minds for the time being. Either--back somewhere in the past without carrying our physical bodies with us; for if we could take our bodies with us, we would be in the present again, and then worry is impossible; or, we use our imagination and project the future entirely apart from our bodies, for we cannot project our bodies into the future, and if we could we would again be in the present. We worry over going to have an operation performed which may or not be dangerous, but quite necessary. We may still think we worry when the operation begins, but as soon as that occurs the time becomes the present, and though we may fear, we cannot worry in the present.

The Story in a Tunnel

How a Tunnel Is Dug Under Water.

Fig. 1. On the left is a cross section showing, in diagram, the back view of a shield. The heavy black circle is the “tail” or “skin.” The small circles within the tail are the hydraulic rams which at a pressure of 5,000 pounds to the square inch force the shield forward. The square compartments within the shield are the openings through which the men pass to dig away the ground. In the middle of the shield is shown the swinging “erector” which picks up the iron lining plates and puts them in position.

The view on the right is a longitudinal section of the tunnel showing the shield and the bulkhead wall across the tunnel with the air locks built into it. The front of the shield ahead of the doors is made with a sharp edge called the “cutting edge” and this makes it easier for the shield to advance in case all the ground in front has not been removed. This view shows how the tail overlaps the last portion of the iron lining.

Some distance behind the shield comes the concrete bulkhead wall with the air locks contained in it. There are two shown in the view. The upper one is the emergency air lock, always kept ready so that in case of an accident the men have a means of escape even though the lower part of the tunnel is filled with rushing water or mud. The lower air lock is for the passage of men and materials during ordinary working. This view also shows that all the tunnel ahead of the bulkhead wall is under compressed air while the finished tunnel behind the bulkhead wall is under the ordinary or normal air pressure. When the tunnel is finished the air locks and bulkhead walls are removed.

HOW TUNNELS ARE BUILT.

These notes describe very generally the way in which tunnels are built through mud and gravel under parts of the sea or large rivers in such a way that the men who build them are protected and as safe as the carpenter who is building a house.

The way these tunnels are built is called the “shield” way because the machine used is called a shield. It is given this name because it shields the tunnel builders from the water and the mud which are ready at every moment to overwhelm them and kill them.

The shield was invented in 1818 by a great Engineer, Marc Isambard Brunel, who was a Frenchman living in England. The idea of the shield came to him as he saw how the sea worm which attacks the wooden piles of docks along the shore bores the holes it makes in the wood. The head of this worm is very hard and can bite its way through the hardest woods. As it goes through the wood its body makes a hard shelly coating which lines the holes which its head has made and prevents the hole from getting filled up. This is the general idea of a tunnel built by a shield.

The first shield was used by Mr. Brunel to make a tunnel across the Thames River at London, England. This is still the biggest tunnel ever built by a shield, although not the longest, and is still used by railroad trains. This tunnel was begun in 1825 and was finished in 1843, and provides a history of almost unexampled and not-to-be-excelled courage in attacking difficulties and skill in defeating them.

Since the days of Brunel many great improvements have been made in the shield and in the way of working it but the same idea is still there.

After the days of Brunel’s shield another great help was given to tunnel builders by the invention of the use of compressed air to hold back the water which saturates the ground in which the tunnel is being built.

~WHO INVENTED THE COMPRESSED AIR METHOD~

The first real invention of compressed air for this purpose was made by Admiral Sir Thomas Cochrane who, in 1830, took out a patent for the use of compressed air to expel the water from the ground in shafts and tunnels and, by this means, to convert the ground from a condition of quicksand to one of firmness. This patent covers all the essential features of compressed air working.

As suggested above, the thing which compressed air does in a tunnel is to push the water out from all the spaces which it fills in the ground, so that the men who are digging away the ground for the tunnel are working in firm dry ground instead of a mixture of earth and water which will run into and fill the hole they dig as soon as it is dug.

Whenever a tunnel is being built below a body of water through ground which is porous, or in other words through any ground except solid rock or dense clay, the water fills every crevice and space in the ground and is exerting a pressure of about half a pound per square inch above the ordinary pressure of the air, (which is 15 pounds to the square inch) for every foot of depth below the surface of the water; so that supposing the tunnel is 40 feet below the water the water has a pressure of nearly 20 pounds per square inch on every square inch of the surface of the tunnel. This pressure causes the water to flow violently into any hole or opening that is made in the ground, and, unless the water is prevented from moving by some means or other, the opening made would be very quickly filled with water and also with ground as the rush of water will carry the sand, gravel or mud with it.

By Cochrane’s invention the whole tunnel is filled with air under a pressure equal to the pressure of the water. This compressed air therefore balances the pressure of the water and holds it back from moving, and if the pressure of the air is made slightly greater than that of the water the water is driven back from the tunnels for a short distance so that when the tunnel is being dug the ground instead of being wet is quite dry.

This explains the principles of the shield and compressed air way of making a tunnel.

The following describes very shortly how these principles are put to actual use.

Most tunnels which are built by shield and compressed air under rivers or arms of the sea are lined with cast iron plates to protect the railway or roadway which is in the tunnel.

The tunnel is a circular tube, or shell, and the plates have flanges on all sides which are bolted together. This shell is put into place, plate by plate, by means of the shield which not only protects the workmen and the work under construction, but which helps to build the iron shell. In fact it corresponds to the sea worm which bores through the wood and lines the hole with a shell. In the case of the tunnel the shell is made of iron. The shield itself consists of a steel tube or cylinder slightly bigger in diameter than the tube or tunnel it is intended to build. The front edge of this shield is made up of a ring of sharp edged castings which form what is called the “cutting edge.” Just behind the cutting edge is a bulkhead or wall of steel, in which are openings which may be opened or closed at will. Behind this bulkhead are placed a number of hydraulic jacks or presses arranged around the shield and within it, so that by thrusting against the last erected ring of iron lining the whole shield is pushed forward. The rear end of the shield is a continuation of the cylinder which forms the front end, and this part, called the “tail,” always overlaps the last few feet of the built up iron shell.

~HOW THE SHIELD CUTS THROUGH THE GROUND~