LOCATING DISTRIBUTION BOX, LAYING MULTIPLE CABLE, AND MARKING OUT MINE
FIELD.
(NOTE.—The operations in Chapters IV and V are
described in what is thought to be the logical order, but
circumstances may alter their sequence, and, in fact,
several of the steps may be carried on simultaneously.)
For the work on the water there will be needed five boats, viz., a mine
planter or suitably fitted-up heavy tug, a small tug or heavy launch
called the distribution box boat, and three launches or yawls. The
capacity of the planter is such that a group of 19 mines can be handled
at one time.
The instructions to be observed by the master of a mine planter in
marking out a mine field and in planting mines are to be found in
Appendix No. 6.
=Determining location for distribution box.=—From an examination of
the chart, or of the approved scheme for mining, the locations of the
lines and groups of mines are determined. A distribution box is to be
placed about 350 feet in rear of the center of each group of mines. The
locations for the distribution boxes are marked on the plotting board
and their azimuths from each of the ends of the horizontal base or
their azimuth and range from the vertical base station are determined.
=Marking location of distribution box.=—An anchor with buoy attached
is placed upon the deck of a small tug and carried out to one of the
selected spots. By a system of signals the boat is directed to the
location determined and there the anchor is thrown overboard. The
locations for the other distribution boxes are marked in a like manner.
=Laying multiple cable.=—The cable-reel is placed upon the forward
deck of the planter and raised on the jacks. The planter then proceeds
as near the mining casemate as the depth of water permits, and one end
of the cable is passed ashore, either by a launch, by yawls, or by any
other suitable method. In case the planter can not approach nearer the
shore than 100 yards it will be necessary to coil more than enough
cable to reach the shore in a figure of eight in a yawl, which is then
towed toward the desired point on shore, the men aboard the yawl paying
out the cable as it proceeds. This end is drawn in through the conduit
or gallery to the casemate or terminal hut. It may be secured by taking
a telegraph hitch around it with a chain and spiking the chain to some
heavy timbers or fastening it to some holdfast. When cable ends have
already been laid they will be picked up and joined to the multiple
cable for the groups.
The shore end having been secured, the planter moves out to the
position of the distribution box, unreeling the cable as it goes.
If the water be very deep, a friction brake must be extemporized to
prevent the reel from overrunning. (While the planter is laying the
cable, the casemate party tags and attaches the shore end as explained
later.) To prevent kinks as far as possible cable should be laid with
as much tension as practicable.
If the cable is not long enough, a second one must be joined to it.
This is preferably done by passing the ends to a small boat. The
junction is made, either using a junction box with Turk’s-heads and
taped joints, or opening back the armor for about 5 feet from the ends,
making taped joints, protecting them with tape, and then rewrapping the
armor and seizing the ends with wire. Care must be taken to join the
proper conductors of the two ends.
In the meantime the distribution box boat with a detachment of one
noncommissioned officer and five men takes the distribution box and
moves out to the spot marked by the buoy. It picks up the buoy and
makes fast to the anchor line.
The planter continues laying the multiple cable until it reaches the
distribution box boat. The multiple cable is then cut and the end
passed to the distribution box boat, usually by a heaving line. The
cable is lashed to the boat; a Turk’s-head is worked upon the end and
then secured in the distribution box. As a precautionary measure for
the recovery of the distribution box, should it be lost overboard
during mine planting, it is well to have the multiple cable buoyed
about 100 yards in rear of the distribution box.
In case it may be desired not to use the distribution box at once, the
separate conductors of the multiple cable should be tagged, tested,
and insulated. The cable should be buoyed and dropped overboard to be
recovered subsequently.
=Identifying, tagging, and testing the conductors of the multiple
cable.=—_Tagging._—In the casemate the conductors are separated,
carefully identified, tagged, and attached to the corresponding
terminal of the terminal bar on the operating board. The mine switch
for No. 19 is opened and the telephone terminal attached to its stud
so as to use No. 19 for communicating with the distribution box boat.
The ends in the distribution box boat are separated, one terminal of a
boat telephone is attached to No. 19, and the other earthed either by
attaching to the cable armor or to an earth plate hanging overboard in
the water. Communication is thus established with the operator in the
casemate. Nos. 1, 13, and 19 are picked out easily; the remaining ones
are tagged in contraclockwise direction.
_Verifying the tagging._—The casemate is then notified that the boat
party is ready to check the tagging. This is done as follows: The power
switches on the operating board are all closed, except 19, and direct
current put on the cable by closing switch No. 3 up. The casemate
operator then directs the boat party to earth in regular succession the
various conductors. This is done most quickly by touching the conductor
to the cable armor. The corresponding automatic switch on the operating
board should drop. Any errors in tagging detected by this test should
be corrected at once. This test also checks the continuity of circuit
of each conductor.
_Insulation test._—The operator then directs the boat party to prepare
the cable end for insulation test. This is done by separating the
conductors, holding them in the air, and drying them if necessary.
When prepared, word is sent to the casemate operator, who tests as
follows: He closes switch No. 7 up. This throws D. C. power on the
mil-ammeter plug of the operating board and introduces in the circuit
the mil-ammeter and its protective lamp. The green lamp is then
unscrewed and the mil-ammeter plug used on the D. C. jaw.
If there be no leak in the multiple cable, since the ends at the
distribution box boat are held in the air, there will be no appreciable
reading of the mil-ammeter.
If there be a leak, this fact will be revealed by a reading on the
mil-ammeter. To discover the particular conductor or conductors on
which this leak exists, each power switch is opened in succession and
the mil-ammeter plug inserted on the jaw of the power switch.
No. 19 is now tested in the same way by first shifting both telephones
to No. 1, the boat end being held in the air. The operator reports the
result of the test.
Upon completion of these tests the power is turned off. Post power
should not be used for testing, because the negative side of the post
power may be grounded.
=Marking out the mine field.=—In using automatic anchors it is not
necessary to mark the mine field; but in using mushroom anchors it is
generally done. The material required consists of 1 measuring line with
reel and frame, 5 anchors, 5 keg buoys, and 5 raising ropes.
A buoyed anchor is dropped about 350 feet in front of the
distribution box buoy. This marks the position of mine No. 10 and of
the center of the group.
This marking buoy is picked up by a launch which makes fast to the
anchor rope. The planter now passes to the launch one end of a
measuring line, which has marks at 280, 300, 350, 580, and 600 feet.
These marks may be made by painting 3 feet of the measuring line
some distinctive color at the designated points. The planter moves
out slowly along the line to be occupied by the mines, unreeling the
measuring line as it goes, and drops buoys at the 300 and 600 foot
marks. It then returns and does the same for the other side of the
line. These five buoys mark the line to be occupied by the mines,
indicate the positions of mines Nos. 4, 7, 10, 13, and 16, and in
addition cut up the distance into 300-foot lengths, which enable the
planter to plant mines at a close approximation to 100 feet apart.
=Taking soundings on line of mines.=—When automatic anchors are used,
such information as may be required about depth of water may usually
be obtained from charts. This may not be sufficiently accurate for
planting with ordinary anchors. In the latter case soundings must be
taken at the spots where the mines are to be planted.
These soundings are made from the launches. The launches take a
measuring line marked at every 100 feet, stretch it between the planted
buoys, and take the soundings at every 100-foot point. The soundings
are recorded in a blank book showing the number of the corresponding
mine and state of the tide. It may be found more satisfactory to hold
one end of the measuring line at the buoy and circle across the line of
mines with the launch, getting the sounding at the point of crossing.
=Preparing mooring ropes.=—The mooring ropes are cut off with square
ends, and the ends passed through the holes in the mooring sockets. The
strands and wires are untwisted and spread out for a length equal to
the length of the socket hole. The rope is pulled back until the ends
are about flush with the top ends of the hole; a piece of marline is
tied about the rope below the socket. If necessary to hold the socket,
a piece of burlap may be wrapped around below the socket, and a fold
allowed to fall over the hand. Generally, means can be found to set
the socket upright while pouring full of alloy. The alloy consists of
9 parts of lead and 1 part of antimony melted together. A melting pot
heated by a plumber’s furnace, or preferably a Khotal lamp, is used for
this purpose. Great care must be taken to see that there is no oil or
water on the socket or mooring rope before pouring the alloy.
The length of the mooring rope for buoyant mines No. 32 equals the
depth at low tide, less 15 feet. This allows 5 feet for the length
of the mine, anchor, and shackles, and 10 feet for submergence. When
thimbles and clips are used the mooring rope is cut 3 feet longer and
is bent back a foot and a half at each end for the thimbles and clips.
For the larger mine cases, an additional allowance must be made for the
length of the cylindrical part of the case.
Each mooring rope is carefully tagged at each end with the number of
the corresponding mine.