568 NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE
exposed, and cleaned and coated where necessary. Special attention
should be given to the examination of the ash shoots, and the shell
plating in way of the openings.
5. In cases hi which the inner siirface of the bottom plating is
coated with cement or asphalt, the removal of this coating may bo
dispensed with, provided it be carefully inspected, tested by beating
or chipping, and found sound and adhering satisfactorily to the
steel.
6. If the vessel has a double bottom a sufficient amount of ceiling
is to be removed to enable the condition of the tank top to be
ascertained, and if it is found that the plating is free from dirt and
rust, the removal of the remainder of the ceiling may, in the case
of the First Special Survey, be dispensed with.
7. The double bottom tanks are to be tested by a head of water
to the light water-line, but in no case less than 8 feet above the
inner bottom. Double bottom compartments, which are used for the
carriage of oil fuel, are to be tested by a head of water extending
to the load water-line, or by a head sufficient to give the maximum
pressure which can come upon, them in practice, whichever is the
greater.
Where peak tanks or other deep tanks for carrying water ballast
are fitted, their watertightness is to be tested by a head of water
not less than 8 feet above the crown of the tank.
All water ballast tanks are to be cleaned out to admit of their
being properly examined inside, special attention being given to the
tanks under the boilers.
All peak tanks, deep tanks and bunkers specially constructed
for carrying oil fuel are to be examined internally and are to be
tested by a head of water equal to 30 per cent, of the depth of the
tank, or 8 feet, whichever is the greater, provided the tanks are
fitted with overflows or other means to prevent a greater pressure
than indicated above. Where the tanks are not fitted with over-
flows or other similar devices, they must be tested by a head
sufficient to give the maximum pressure which can be experienced
in practice.
In the case of motor and other vessels burning oil fuel and
carrying it in the double bottom and other tanks, upon the occasion
of the First Special Survey No. 1 these tanks, with the exception of