SECTION
Fig. 3.
This horse-shoe indentation extends nearly to the other end of the cylinder, a thin layer of the metal only intervening. This is graduated on the outside into equal parts representing seconds and quarter seconds ([see Fig. 4]). In the bottom of this channel a smooth layer of the composition is placed, with a piece of wick or yarn underneath it. On this is placed a piece of metal, the cross section of which is wedge shaped ([see Fig. 3]); and this, by machinery, is pressed down upon the composition, sealing it hermetically. The cylindrical opening represented at [a Fig. 2], is filled with fine powder and covered with a sheet of tin, which is soldered, closing the magazine from the external air.
113]
Before using the fuze, several holes are punched through this sheet of tin, to allow the flame to enter the shell. On the side of the fuze the thread of a screw is cut which fits into one cut on the inside of the fuze-hole, and the fuze is screwed into the shell with a wrench.
Fig. 4.
The thin layer of metal over the composition is cut through with a gouge or chisel, or even a pen-knife, at the interval marked with the number of seconds which we wish the fuze to burn. To prevent the metal of this fuze, which is soft, from being driven into the shell by the explosive force of the charge, a circular piece of iron, with a hole through its centre, and the thread of a screw on the outside [Fig. 5] is screwed into the fuze-hole before the fuze is inserted.
