The helmet is made of tinned copper, with three circular glasses, one
in front and one on either side, with guards to protect them. The
front eye-piece is made to unscrew and enable the diver to receive
or give instructions without removing the helmet. One or more outlet
valves are placed at the back or side of the helmet to allow the
vitiated air to escape. These valves only open outwards by working
against a spiral spring, so that no water can enter. The inlet valve
is at the back of the helmet, and the air on entry is directed by
three channels running along the top of the helmet to points above the
eye-pieces, enabling the diver to always inhale fresh air. The helmet
is secured to the breastplate below by a segmental screw-bayonet joint,
securing attachment by one-eighth of a turn. The junction between the
water-proof dress and the breastplate is made watertight by means of
studs, brass plates and wing-nuts.
A life or signal-line and also a modern telephone enables the diver to
communicate at all times with those above him.
The cost of a complete diving outfit ranges from $750.00 to $1,000.00.
The weight of the armor and attachments worn by the diver is 256
pounds, divided as follows: Helmet and breastplate, 58 pounds; belt of
lead weights, 122 pounds; rubber suit, 19 pounds; iron-soled shoes, 27
pounds each.
The air which sustains the diver’s life below the surface is pumped
from above by a powerful pump, which must be kept constantly at work
while the diver is down. A stoppage of the pump a single instant while
the diver is in deep water would result almost in his instant death
from the pressure of the water outside.
The greatest depth reached by any diver was 204 feet, at which depth
there was a pressure of 88¹⁄₂ pounds per square inch on his body. The
area exposed of the average diver in armor is 720 inches, which would
have made the diver at that depth sustain a pressure of 66,960 pounds,
or over 33 tons.
The water pressure on a diver is as follows:
20 feet 8¹⁄₂ lbs.
30 feet 12³⁄₄ lbs.
40 feet 17¹⁄₄ lbs.
50 feet 21³⁄₄ lbs.
60 feet 26¹⁄₄ lbs.
70 feet 30¹⁄₂ lbs.
80 feet 34³⁄₄ lbs.
90 feet 39 lbs.
100 feet 43¹⁄₂ lbs.
120 feet 52¹⁄₄ lbs.
130 feet 56¹⁄₂ lbs.
140 feet 60³⁄₄ lbs.
150 feet 65¹⁄₄ lbs.
160 feet 69³⁄₄ lbs.
170 feet 74 lbs.
180 feet 78 lbs.
190 feet 82¹⁄₄ lbs.
204 feet 88¹⁄₂ lbs.
The dangers of diving are manifold, and so risky is the calling that
there are comparatively few divers in the United States. The cheapest
of them command $10.00 a day for four or five hours’ work, and many of
them get $50.00 and $60.00 for the same term of labor under water.
The greatest danger that besets the diver is the risk he runs every
time he dives of rupturing a blood-vessel by the excessively compressed
air he is compelled to breathe. He is also subject to attacks from
sharks, sword-fish, devil-fish, and other voracious monsters of
the ocean’s depths. To defend himself against them, he carries a
double-edged knife as sharp as a razor. It is the diver’s sole weapon
of defense.
Just how far back the art of submarine diving dates is a matter of
conjecture, but until the invention of the present armor and helmet,
in 1839, work and exploration under water was, at best, imperfect, and
could only be pursued in a very limited degree.
Feats of Divers.
~THE GREATEST DIVING FEAT~
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.
[Illustration: The last look just before going down.]
[Illustration: Coming up after a successful trip.]
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.
[Illustration:
_Back View of Shield_
_Longitudinal Section through Shield & Tunnel_
_Diagram showing method of tunnel construction by shield and
compressed air._
_Scale; ¹⁄₈ inch · 1 foot_
_Jacobs & Davies Inc. 30 Church St. N.Y._
_Oct. 15. 1910._