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ability. I could not, even if there were time, give you every detail, but it seems to me that with a clear
understanding of the principles involved, careful observation and common sense, it should be possible, on
the spot and in co-operation with an interested Marine Superintendent or Ship's Officer, to make useful
recommendations in regard to any rat-proofing problem which may arise. The proposals put forward
refer to new construction and may not be applicable to existing ships, but they will serve as a standard which
should be approached as nearly as is reasonably practicable and necessary in each case. We cannot go
ahead at the pace which has been set in New York by the enthusiasm and expert knowledge of Mr. Holsendorf.
We must proceed more slowly, taking the shipping companies with us. But appreciation of the value of
rat-proofing is spreading amongst marine superintendents and ship's officers, and it is possible to get much
good work done when there is evidence of rats; when there is no evidence we can at the present stage deal
only with the more obvious and easily corrected harbourage. Nevertheless, even in the absence of ratinfestation,
I think harbourage should be recorded on Deratisation Exemption Certificates. We must not
let shipowners consider that their ships are rat-proof because no harbourage is recorded on Form Port 11.
Nor must we expose ourselves to criticism abroad for failure to complete these certificates properly.
"My instructions to my own Inspectors are as follows: 'In every compartment say to yourself, is
this compartment rat-proof? If your answer is 'No' then put down all the reasons why it is not rat-proof,
including all rat-harbourage and all potential rat runs from one compartment to another. If the ship is
rat-free you may be content simply to record the conditions, which will be entered on the Exemption
Certificate, and to draw the attention of the marine superintendent or the master to the desirability of
rat-proofing. If on the other hand there is evidence of rat-infestation you should not only point out defects,
but endeavour to get as many as possible corrected.'
"I will first of all describe the principal defects as regards rat-proofing in ships and suggest how they
should be dealt with in new construction. Then I will suggest what should be done in regard to ships
in commission, but every opportunity should be taken to approach as nearly as possible to the
recommendations for new ships. I will deal with the sections systematically beginning with the holds, but
you will appreciate that each ship has its own particular problems which provide scope for the inductive
and constructive reasoning of the Inspector.
"Holds'—Ceiling over Tank Tops and Bilges.—In many ships there is a wooden flooring, termed
the ceiling, over the top of the double-bottom tanks, raised on battens one to two inches thick. The
space between this wooden ceiling and the tank tops forms ideal rat-harbourage. The remedy is to
omit the wooden ceiling altogether or to fit the planks closely to the tank top and bed them in Stockholm
tar or cement.
"If fuel oil is carried in the tanks the Ship Classification Societies require the ceiling to be raised on
battens one-and-a-half to two inches thick. In these cases, or if for any other reason ceilings cannot be
eliminated, they should be fitted tightly and protected from gnawing by strips of galvanised sheet metal
six inches wide, at all angles and edges, and also where stanchions, pillars or pipes pass through them.
"There is often access to the space under the ceiling from the bilges at the margin plate. This access
should be closed by a flange of sheet metal perforated so as to allow drainage along the tank tops into the
bilges. Sometimes there is no wooden ceiling over the bottom of the holds, but only a cargo pad under the
hatches. This should be flashed with metal all round the edges if there is rat-harbourage underneath.
"Spaces between Frames at Ship's Side—Lower Hold.—At the ship's side, in the lower holds, the
space between the frames is commonly closed by light wooden fillers covered with a thin layer of cement,
which frequently gets broken, providing holes through which rats can get into the bilges. Either the
ceiling should be made tight round the frames and the edges be flashed with metal, or the concrete filling
should be at least two inches thick and be reinforced with expanded metal or wire mesh.
"Permanent Wooden Bulkheads.—If permanent wooden bulkheads are required to protect cargo
from tank leakage there is harbourage between the wooden and the steel bulkheads. The wooden bulkhead
must therefore be of thick, tongued-and-grooved boarding, fitted snugly and flashed all round the edges and
where pipes or structural members pass through. An open sparred type of bulkhead installed in a horizontal
manner on vertical framing is preferable.
"Pipe Casings, &c.—There are always pipes running through holds, and these must be protected
against damage from cargo. Commonly they are completely boxed in with wood, forming ideal ratharbourage
and a means by which rats may get from one compartment to another. Pipes may be vertical
or horizontal. In the case of vertical pipes or overhead horizontal pipes the protection should be of open
type construction, either wooden spar type or face board type of flat or half-round steel batten type. In the
case of pipes on the bottom of the hold it may be necessary to box them in completely. This should be done
with steel, or if with wood, all edges should be flashed with metal.
"Pillars.—Pillars or girders may be cased: again an open type of casing should be used. There may
be lightening holes in pillar foundations. These should be protected. At the top of pillars there may be
wide shelf-like compensating plates to which rats have access via the beams, and where they may nest.
This space may be filled in with cement.
"Openings for Pipes.—Holes through bulkheads for pipes, &c., are frequently cut too large and afford
passage for rats. These openings should be closed by a sheet metal collar round the pipe. If the pipe is
insulated, and the insulation is a half-inch or more thick and is continued through the bulkhead, rats might
get through by gnawing away the insulation. To prevent this a sheet metal cylinder should be fitted round
the insulation for twelve inches on each side of the bulkhead.
"Permanent Ballast should be stowed in rat-proofed casings.