Fig. 218. Western Union Type Mica Fuse
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Enclosed Fuses:—If a fuse wire within an insulating tube be made to connect metal caps on that tube and the space around the tube be filled with a non-conducting powder, the gases of the vaporized fuse metal will be absorbed more quickly than when formed without such imbedding in a powder. The filling of such a tubular fuse also muffles the explosion which occurs when the fuse is vaporized.

Fig. 219. Pair of Enclosed Fuses
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Fuses of the enclosed type, with or without filling, are widely used in power circuits generally and are recommended by fire insurance bodies. Fig. 219 illustrates an arrester having a fuse of the enclosed type, this example being that of the H. W. Johns-Manville Company.