116 32 
mace fast the drift was sufficient to keep everything taut and in line, except on flat 
cal days, when a touch of the screw was needed. After the first few shots it was 
found that in even moderate breezes the drift was sufficient to draw the gauge lines 
somewhat out of the vertical, with the result that the distances from charge to gauges 
became inaccurate ; this was remedied by introducing a light hemp bottom-line at a 
level just above the charge. The general arrangement will be seen from the example 
shown in lig 40. A diagram of this sort was made out for each shot, for record and 
for the guidance of the working party. It is obviously not to scale, but all distances 
are shown by figures; for example, the first gauge line is 91} feet beyond the charge, 
and carries two gauges GF38, GH1 at depths of 53 feet and 54 feet. Beyond the four 
gauge lines are two II lV. mine cases, serving as damage gauges ; these also are 
correctly distanced by the bottom-line. 
The floats are not shown in the diagram. Fishermen’s buffs proved to be the 
most convenient floats for supporting the gauge lines, but the charge was generally 
ling from a cask; heavy charges were hung from an empty Mark III. mine case, or, 
when necessary, from a pair of these cases. The gauges were shackled by their 
evebolts to grommets in the gauge lines (Fig. 55), which were 14-inch steel wires. 
The gauges were usually hung one foot apart and as nearly as possible at the same 
level as the charee. The bottom-line also was shackled to a grommet on each gauge 
line, but its attachment to the charge line was by means of a shackle embracing the 
charge line in such a way that the charge could spin without twisting up the bottom- 
line, The charge was generally hung by a 1}-inch steel wire but was lowered by a 
separate hemp line; after the charge was lowered the hemp line was left hanging 
slack, with its end hent on to the grass about 20 feet from the charge line, to provide 
for the recovery of the charge in case of missfire; a similar line was attached to the 
sinker of each of the H 1V. mines; these ropes, as well as the firing-circuit, are 
omitted from the diagram for the sake of clearness. The “ Malapert’’ was generally 
300 feet from the charge, but this distance was increased for charges of more than 
300 Ibs. 
The arrangement illustrated in Fig. 40 is typical of the great majority of the 
shots fired, though many of them were much simpler; frequently there were only two 
gauge lines at equal distances on opposite sides of the charge. On some occasions 
gauges were hung directly beneath the charge, as in Fig. 43. The experiments with 
long charges, described in Section 15, required special provision for keeping the axis 
of the charge parallel to the grass hawser; this was effected by a bifilar suspension, 
as shown in. Fig 41, the suspension wires being bent on to the ends of a 12-foot 
plank, lashed to the grass, with a barrel at each end. Gauge lines were hung from 
the grass on both sides of the charge, with bottom-lines secured to the ends of the 
charge, and a third gauge line was hung from a transverse surface line, consisting 
of a light hemp rope with small floats, which was kept at right angles to the grass by 
the ship’s dinghy, the bottom-line from this gauge line being secured to the middle 
of the charge. 
The experiments in which charges were fired on the bottom (Section 10) required 
au entirely different scheme. The arrangement is shown in Fig. 42 The gauges 
were threaded by their eyebolts on a copper tube and lashed in position about one 
foot apart. A steel wire was rove through the tube and bent on to the erds of a 
plank, the length of wire being such as to support the tube ai a distance of JO feet 
from the plank. The middle of the plank was lashed to the grass hawser, with 
bridles to its ends to keep it square. The charge, consisting of 1,000 Ibs. T.N.T., 
was lowered to the bottom in 10 fathoms by a hemp line, with marks at 75 feet and 
105 feet from the centre of the charge. As soon as the charge reached bottom the 
hemp was made fast, so as to anchor the ship, while the two marks were lashed to 
the middle of the gauge tube and plank respectively. The gear was then let go and 
the ‘‘ Malapert” allowed to drift until 450 feet of grass had been veered, when the 
hawser was made fast. The firing of the charge was delayed until two fishermen’s 
buffs on the ends of the plank were observed to show signs of submerging, owing to 
the strain put on the grass hawser by the vessel’s drift ; by this means it was ensured 
that the system was thoroughly taut and the distance of the gauges correct at the 
moment of firing. 
The plank and cross-bar device described in the previous paragraph was also 
used in some of the experiments described in Section 8, when a line of gauges had to 
be supported at a depth of only a few feet below the surface. 
