and firing mechanism in a separate bl10y called a " contact buoy ...

4IO() TEXT BOOK OF ORDNANCE AND GrNNERY
work is commenced simultaneously, each digger beginning at the
left of his task, and getting cover to the required depth as quickly
as possible, and then extending the excavation to his right.
\Vith ditches, place the diggers along the escarp line, facing
the work, each with a pick and shovel, at intervals of 6 feet.
Shovelers are placed upon the ground to be occupied by the parapet,
in the proportion of two to each set of three diggers (the
whole number being, therefore, one-third less than that of the
diggers) ; these have shovels only. Rammel's are placed in the
proportion of one to each pair of shovelers, in order to consolidate
the earth; they should not allow more than 6 inches in
depth to accumulate without ramming it well. Suitable instruments
for their use are of very easy construction. The ramming
is not done with a view of resisting projectiles, as loose earth
will do this better, but with the object of solidifying the work.
7. Revetments.-Earth newly dug up will not stand at the
steep slopes required for some portions of the work; the means
used to effect this are called revetments; hltrdles or mats, 6 feet
long and 2 feet 9 inches high, and made of brushwood with vertical
pieces called pickets may be readily formed; IO pickets will be
a good number for each hurdle. A gabion is a cylindrical hurdle,
filled with earth when placed in revetment; gabions are 2 feet in
diameter and about 3 feet high; fascines, or bundles of brushwood,
from 7 to 9 inches in diameter, and of various lengths, are very
good for this purpose; they are bound together by tough twigs, at
intervals of about I8 inches; this revetment is built as the parapet
is raised, and secured to it by means of pickets driven into it at
angles of 45 0 , each row of fascines being also picketed to the row
beneath; the joints of the rows of fascines should be broken; it is
necessary to use revetments for the interior slopes and cheeks of
t>mbrasures; if fascines cannot be procured, planks, casks or sand
bags may be used for this purpose. Magazines are frequently
constructed on the unexposed sides of traverses, as follows: Place
strong splinter-proof timbers at an angle of 45 0
against a welll'evetted
traverse, strengthened by bags of earth and sods, the
whole being covered with tarpaulins.
8. Obstacles.-Obstac1es have for their object the holding of
an enemy under fire while checking his advance and breaking up
his formation.