The Float (Figure 227). The float was originally designed to be a simple sphere of 16 inches diameter. It was found, however, that it was unstable in tidal streams. Conse-quently two retractable fins were fitted; also the mooring point was moved from the base of the float to allow the mooring cable freedom of movement. In addition, a heavy counterweight was added in the base. With these modifications it was found to be com-pletely stable in tidal streams having a speed of up to four knots; and 5° tilt was said to be the maximum.

The float is constructed of mild steel 1/16 inch thick, welded together. Because of the awkward shapes of the fan and cable pocktes, it was found that it was not strong enough for depths greater than 15 to 20 fathoms.

The float is normally carried in a hemispherical recess in the rear end of the mine case and is ejected from it when laid, by means of a spring. This spring is held back by a catch that is released by an impact switch, which fires an explosive release.

Figure 227