168 Abel's Fuses and Wheat-stone's Exploder. 



ends of the conducting wires, which were separated very 

 slightly, but effectually, with the fuse itself. The passage of 

 the spark across the small space between the wires ignites 

 the composition, and thence the gunpowder. This composi- 

 tion, Mr. Ellery stated, was the result of considerable experi- 

 ment and research on the part of Mr. Abel, the patentee, 

 the chemist to the War Department. It consists of a mixture 

 of a Phosphide and a Sulphide of Copper with Chlorate of 

 Potash, in such nicely balanced proportions that it offered 

 just sufficient resistance to the passage of the electric spark 

 to # ensure ignition, but not sufficient to hinder the passage 

 of a moderately weak spark. 



After practically illustrating the efficacy of the exploder 

 in firing these fuses through considerable lengths of insulated 

 wire, Mr. Ellery proceeded to show the great facility and im- 

 munity trom accident this method of firing gunpowder offered 

 in mining and other engineering operations, and pointed out 

 with what simplicity arrangements could be made in large 

 mines for adopting it. He remarked that it not only admitted 

 of a very considerable number of blasts being fired at the same 

 moment from a considerable distance, but would tend to 

 obviate entirely those accidents so frequently occurring 

 through the smouldering of the ordinary tube fuse. He 

 further drew attention to the great superiority of the ex- 

 ploder and Abel's fuses to the ordinary method of firing- 

 gunpowder by electricity, by means of a powerful voltaic 

 battery, especially in submarine operations. 



