and a main charge at the back to throw the fuel forward. An important discovery was that including magnesium alloy turnings (the waste product of machining magnesium pieces in a lathe) with the main charge at the rear of the barrel would give reliable ignition. This eliminated the need for a separate ignition charge and its associated wiring. The alloy of about 90% magnesium and 10% aluminium was, at the time, known under the trade name Elektron. Design variations Of the original British flame fougasse designs, there were three main variants: the safety fougasse, the demigasse and the hedge hopper. They all used metal barrels and similar pre-prepared explosive charges, although they varied in the details of construction and the amount of ammonal used for the propelling charge. Safety fougasse The most common form of the flame fougasse was the safety fougasse. This design allowed the propelling charge to be stored separately until needed. The safety fougasse was constructed as follows: a small section was excavated from the side of a slope, leaving a shallow platform of earth, and a barrel of incendiary mixture was placed horizontally in a low position with one round face pointing towards the target. At the back, a section of stove or drain pipe was placed vertically against the rear face of the barrel. The lower end of the pipe was blocked off with a thin cover and positioned a few inches above the bottom of the barrel. The top of the pipe was fitted with a loose cap to keep water out. This pipe is what makes it a "safety" fougasse because it allows later installation of the propelling charge. Soil was then built up over the weapon until all that could be seen were the front disk of the barrel and top of the pipe. The propelling charge was prepared with an electrically triggered detonator in a primer bound with insulating tape to three or four cartridges of ammonal explosive. This assembly was placed in a small, waterproof rubber bag that was, in turn, placed inside a used cocoa tin. of magnesium alloy turnings were added to ensure ignition of the fuel. The electrical wires were passed through a small hole in the lid of the tin which was then tightly fitted. The propelling charges were kept in storage, only to be deployed when enemy action was imminent. To activate the device, the