Without the diver, treasure-hunting beneath the waves would be
impossible. The salvage expert may make the most brilliant plans,
collect the most up-to-date and scientific plant to assist him, but
in the end it is the diver who carries the work through, and upon
the courage, determination and skill of the diver the success of the
expedition depends. To dive to a depth of 5 fathoms, or 30 feet, is a
task that the average man could accomplish without much difficulty;
most men, too, would be able to reach a depth of 10 fathoms or 60 feet,
if they were in decent physical condition. But at 15 and 20 fathoms
and over the body is called upon to stand exceptional strains and so
exceptional men are necessary.
Quite apart from the many risks, deep diving is very arduous, and
seldom are men found with the physique that will enable them to dive
100 feet and over. The deep-sea diver must be trained like an athlete,
perfectly sound in wind and limb and heart, and in tip-top physical
condition. A fat diver stands little chance of attaining great depths,
so the finest divers are generally on the slim side, men without an
ounce of superfluous fat and with muscles tough as steel.
The physical strain placed on the body and heart merely by diving to
these great depths is not generally realized. To ask the human body to
undergo pressures three, four and five times greater than atmospheric
pressure is expecting the body to undergo strains three, four and five
times greater than the body was built to stand. It is like expecting a
motor-car, designed for a load of 30 cwt., to carry a load of 6 tons.
We should not expect the car to do that. Yet we not only call upon the
human body to perform similar feats, but the body actually does perform
them without collapsing.
The crack sea-diver is almost as difficult to find as the swimmer who
can conquer the English Channel. When it comes to doing actual work at
depths of 100 feet and over, the strain on the diver’s body is indeed
very much greater, for his exertions use up so much oxygen that his
heart is called upon to pump at an increased speed in order to replace
it. All the time, of course, the diver is breathing compressed air,
thus the pressure of the sea on the outside of his body is practically
counterbalanced by the pressure of the air inside his body. While the
weight of the sea is trying to crush him inwards, the compressed air
is pushing outwards, so the air pressure within equalizes the water
pressure without, and the diver is enabled to work in perfect safety
under a mass of water that would crush an unprotected man flat.
We might liken the water pressure to six men who are pushing hard
against a door and striving to open it, while the air pressure
resembles six men pushing against the other side of the door to keep it
closed. With both teams equally matched in strength, the door remains
quite unaffected by the contest if it be solidly built of oak. But
if it is a weak door, the strain of the men pushing against it will
probably break it.
Breathing compressed air not only places a strain on the lungs, but
it tends to fill the body with an excess of nitrogen. This nitrogen
may easily form tiny bubbles of gas, and these bubbles, if they reach
the heart, might cause the death of the diver or bring on that dread
paralysis known as diver’s palsy, a disease which renders the lower
part of the diver’s body quite useless.
Strangely enough, it is not in going down that this danger threatens
the diver, but only in coming up. If he comes up too suddenly, the
excess of nitrogen in the blood bubbles like the tiny bubbles in a
siphon of soda and at once his life is threatened. The bubbles are
due to the pressure of the water on the outside of the body growing
suddenly less than the pressure of air inside the body, consequently
the nitrogen seeks to escape in bubbles just as the soda-water seeks
to escape when the key of the siphon is depressed. The pressure inside
the body cannot adjust itself quickly enough to the lessening pressure
outside, and these bubbles are the result.
To avoid this risk, it is necessary for the diver working at great
depths to come up very slowly. He may slide down the shot-rope to
a depth of 120 feet in a few seconds, but, should he stay longer
than half an hour at the bottom, he must not come up in less than
fifty-seven minutes if he would avert danger. He may come up to 40 feet
in eighty seconds, or at the rate of a foot a second. Then he must rest
and exercise his legs and arms on the shot-rope for five minutes before
ascending another 10 feet to the 30-foot level. Here he must rest for a
further period of fifteen minutes, and do those exercises which help to
rid his muscles of their excess of nitrogen. Ascending another 10 feet,
which brings him to within 10 feet of the surface, he is compelled to
rest for twenty-five minutes to allow the excess of nitrogen to pass
from his blood, after which he may rise to the surface.
If a diver happened to remain an hour at a depth of 200 feet, he would
have to spend four hours in coming to the surface to avoid any ill
effects. The exceptional diver who is able to reach this depth should
not, however, remain at the bottom for more than twelve minutes. This
is the safe time, and he can then make the ascent to the surface in
thirty-two minutes.
Remarkable diving experiments were carried out by the British Admiralty
some years ago, during which naval divers attained the record depth
of 210 feet, a record that was long unbeaten. As a result of these
experiments, tables were drawn up showing the time that a man might
remain in safety at certain depths, and indicating the rates at which
he could come to the surface and the depths at which he must rest to
allow the pressure inside his body to adjust itself to the pressure of
the water outside. These tables are followed the wide world over, and
they have made diving one of the safest of occupations, despite the
grave risks the diver is continually running.
Diving was, in fact, so dangerous that exceptional precautions had to
be taken, with the result that the diver who walks about the bottom of
the ocean to-day may be far safer than a man walking across Piccadilly
Circus. The safety of the diver is most carefully watched over, but no
one can foretell when a motor vehicle is going to run down some one
crossing a busy road.
Never was knight attired for the tourney more carefully than the modern
diver is clad before venturing into the depths. It is cold working
at the bottom of the sea, and to guard against the cold the diver
dons warm woollen sweaters and socks, sometimes wearing two or three
sweaters and two or three pairs of thick socks. When he is dressed in
his woollies, the diving dress is fastened about him just as the armour
was fastened on the knights of old. There is a certain ritual about
the performance which must be obeyed. First of all the shoulder pads
are carefully tied on to take the weight of the head-dress, then an
assistant helps him into the rubber diving dress and opens the tight
cuffs for the diver to slip his hands through. The diver sits down
while the assistant ties up the inner collar of the diving-dress and
adjusts the various screws that are to secure his helmet. But before
that is fastened into place the feet are slipped into the boots, each
with its 16 lb. sole of lead.
Ever so carefully the diver’s helmet is put on, for his life depends
upon it being properly fastened. The air-pipe must be carried from the
back of his helmet up under his arm to the front of his body where he
can reach it easily and yet not find it in his way. The air-pumps and
the valves in his helmet are most carefully tested to see that they are
working properly. Then the diver gets on the ladder leading overboard
and a lead weight weighing 40 lb. is adjusted across his breast and
another similar weight is fastened over his back to enable him to sink
to the bottom. The glass of his helmet is screwed up, the pump is set
going, the diver waves his hand to indicate that all is in order, and
the attendant after a final look round gives the diver a smart tap on
the top of the helmet to inform him that he may go down.
Thenceforward the life of the diver is in the hands of the attendant,
who never lets go of the lifeline and air-pipe until the diver comes
to the surface again, feeling the diver at the end of the pipe just as
an angler feels a fish at the end of a line, taking in the slack pipe
to prevent it fouling rocks and wreckage, paying it out as the diver
requires.
The coming of the submarine telephone has certainly lessened the risks
of the diver, for he can now talk to the men in the boat and tell them
what he wants and how he feels. If anything goes wrong and his lines
become entangled, he can inform those at the surface, who can quickly
send down another diver to assist him. In comparatively recent days
it was necessary to signal by means of the lifeline and air-pipe, a
certain number of pulls meaning certain things in accordance with a
code in use by all divers. When a diver wished to convey a special
message he had to signal for a slate to be sent down, and on the slate
he would write what he wanted to convey. It was a slow and cumbersome
method which has been rendered obsolete by the submarine telephone,
which was invented by that famous submarine engineer, R. H. Davis, the
head of Siebe, Gorman & Company.
For ages men have dived for sponges and pearls, remaining at most not
more than a couple of minutes at the bottom. The ancients were fully
alive to the advantages of an invention that would assist men to remain
under water for considerable periods, and they were puzzling their
heads about diving dresses centuries ago. These early inventions,
however, were very crude, one being a sort of barrel with holes through
which the arms could be passed, another a metal cylinder which covered
the head down to the waist where it fitted into leather breeches. Very
strange and wonderful they appear to modern eyes.
No less strange and decidedly more wonderful is the up-to-date diving
dress which has grown out of the invention of Augustus Siebe in 1819.
For eighteen years Siebe experimented with his first type of diving
dress before he achieved, in 1837, the form of dress which is closely
followed to-day. Various people have added improvements, but Siebe’s
form of dress is the one in common use, and the firm of Siebe, Gorman
& Company which he founded to supply his diving dresses are to-day the
greatest submarine engineers in the world.
Inventors have for long been concerned with the problem of a diving
dress that will allow a diver to go to any depth without danger. The
greatest risk of course, is that he will be crushed to death by the
pressure of the water, and to overcome this danger more than one
man has invented an all-metal diving dress with flexible joints. In
appearance these diving dresses seem cumbersome, and the diver looks
more than ever like a knight in armour.
Another form of dress largely in use enables the diver to descend in
shallow water without relying on the usual air-pipe and pump. In such
dresses the diver carries certain chemicals which not only purify
the air he is breathing, but also furnish him with fresh oxygen. One
chemical absorbs the poisonous carbonic acid gas given off by the
breath, and the other chemical gives off fresh oxygen as the moisture
of the breath touches it. The smoke helmet which enables men to enter
a mine after a disaster, or a building full of foul fumes, is equipped
with the same chemicals and made on the same principle as the diving
dress. Instead of completely covering the man, however, this dress is
made like a jacket reaching to the waist, where it is securely buckled.
In this dress it was impossible to penetrate the Redding pit, near
Falkirk, from which five miners were marvellously rescued after being
entombed for nine days, so several naval divers in regulation dress
risked their lives in an effort to penetrate the workings to see if
any other men still survived and to carry stimulants to them. Divers,
at best, have the appearance of creatures from another world, and the
effect of a diver, with his lamp, emerging from the inky water and
coming suddenly on men who had been immured for a fortnight without
food and were at their last gasp had to be carefully considered. Some
of the survivors might have attacked him in their delirium and deprived
their comrades of all chance of succour.
To avoid so untoward an incident, the leading diver carried with him a
message for those men he hoped to find: “This is a diver come to save
you. Don’t touch him, as he cannot speak to you. We are driving a place
for you. Don’t sit down near the water, but keep clear of the damp. If
any of your mates are far through, turn their heads downhill and that
will help them until you are feeling stronger. The diver cannot come up
the hill out of the water to help you, because his tools are too heavy.
He will come back regularly and feed you. You must not drink more than
half a cupful of beef tea each. Wait and take a rest before you drink
another half-cupful. On this paper write who you are. You will be got
out soon.”
Alas, for human endeavour, that message never reached the poor fellows
for whom it was intended! The great falls of roof choked the roads and
proved an insurmountable barrier. Raging, but exhausted, the divers had
to bow their heads in defeat.
So commonplace is the diving dress that it no longer excites curiosity.
Yet it remains one of the wonders of modern civilization. Merely by
utilizing the sap of a tree, which we know as rubber, and fresh air,
men are now able to work and live at the bottom of the sea.