oncerned with
diving as the function of a "diver," whose business it is to go under
water (in modern times, assisted by specially devised apparatus) in
order to work.

_Unassisted or Natural Diving._--The earliest reference to the practice
of the art of diving for a purpose of utility occurs in the _Iliad_, 16,
745-750, where Patroclus compares the fall of Hector's charioteer to the
action of a diver diving for oysters. Thus it would seem that the art
was known about 1000 years before the Christian era. Thucydides is the
first to mention the employment of divers for mechanical work under
water. He relates that divers were employed during the siege of Syracuse
to saw down the barriers which had been constructed below the surface of
the water with the object of obstructing and damaging any Grecian war
vessels which might attempt to enter the harbour. At the siege of Tyre,
divers were ordered by Alexander the Great to impede or destroy the
submarine defences of the besieged as they were erected. The purpose of
these obstructions was analogous to that of the submarine mine of
to-day.

The employment of divers for the salvage of sunken property is first
mentioned by Livy, who records that in the reign of Perseus considerable
treasure was recovered from the sea. By a law of the Rhodians, their
divers were allowed a proportion of the value recovered, varying with
the risk incurred, or the depth from which the treasure was salved. For
instance, if the diver raised it from a depth of eight cubits (12 ft.)
he received one-third for himself; if from sixteen cubits (24 ft.) one
half; but upon goods lost near the shore, and recovered from a depth of
two cubits (36 in.), his share was only one tenth.

These are examples of unassisted diving as practised by the Ancients.
Their primitive method, however, is still in vogue in some parts of the
world--notably in the Ceylon pearl fisheries and in the Mediterranean
sponge fisheries, and it may, therefore, be as well to mention the
system adopted by the natural, or naked, diver of to-day.

The volume and power of respiration of the lungs vary in different
individuals, some persons being able to hold their breath longer than
others, so that it naturally follows that one man may be able to stay
longer under water than another. The longest time that a natural diver
has been known to remain beneath the surface is about two minutes. Some
pearl and sponge divers rub their bodies with oil, and