Composition for percussion caps and fuzes, used in the British service, is made from 6 parts, by weight, of fulminate of mercury, 6 parts of chlorate of potash, and 4 parts of sulphide of antimony. Another cap composition is composed of 12 parts fulminate of mercury, 26 parts chlorate of potash, 30 nitre, 17 sulphur, 14 ground glass, and 1 of shellac varnish. Detonating composition for time fuzes, 6 parts chlorate of potash, 4 parts sulphide of antimony, and 4 parts of fulminate of mercury, this is damped with a varnish composed of 645 grains of shellac dissolved in a pint of methylated spirits, in the proportion of 24 minims to 100 grains of composition. In the manufacture of percussion caps, the copper blanks are cut out and stamped to the required shape from strips of metal rolled to tho required gauge, the blanks are then placed in a gun-metal plate with the con cave side uppermost. A tool, composed of a plate of gun-metal, in which are inserted a number of copper points, each of the same length, and so spaced apart as to exactly fit each point into a cap when inverted over a plate containing the blanks is dipped into a vessel containing the cap com position, which has been previously moistened with methylated spirits, it is then removed, placed over the blanks, and a slight blow serves to deposit a small portion of the cap composition into each cap. A similar tool is then dipped into shellac varnish, removed and placed on the cap, when a drop of varnish from each of the copper points falls into the caps, which are then allowed to dry ; this is a very safe and efficacious method.
In the detonators made in England by the Cotton Powder Co., the fulminate of mercury, while wet, is mixed with very finely ground guncotton and chlorate of potash, about in the proportion of 6 parts of fulminate and 1 part each of guncotton and chlorate of potash.
The water in which the fulminate of mercury is usually stored, is first drained off and replaced by displacement by ether or alcohol, or a mixture of the two. While the fulminate is still moist with ether, the guncotton and chlorate of potash are added, and the mixture well rubbed together.
This compound is next distributed in the detonator shells standing in a frame, and each detonator is put separately in a machine for pressing the paste.
Figs. 623 and 624 are a vertical section and part front view of this machine, with various sections of the rotating table.
A is the table turning with the vertical axis B ; this table carries a number of spindles C, cor responding to the holes D, in whioh the detonators containing the powder are pot for the purpose of being compressed. The spindles C are, in rotation, brought down into the caps by springs H, the motion being controlled by the osoillating disc E, which is kept at a fixed angle by the rollers F.
By rotating the table A it is evident that all the spindles will alternately be depressed, as they travel towards G, and lifted as they travel towards 1), so that the workman may stand in front of the machine without fear of any cap injuring him by explosion. There are other spindles below the holes D. As the table rotates the lower ends of these spindles_ come in succession against the periphery of the lifting wheel K, are lifted, and eject the loaded tubes from the holes D.
This machine has received some modifications since its first introduction, and been so arranged that instead of one, a large number of detonators can be pressed at one time; it is so surrounded with guards that any explosion taking place cannot possibly effect the operator, the detonators being also pressed whilst containing a certain per centage of moisture instead of dry, suitable means being provided for afterwards dispersing this moisture.
Bibliography.—T. M. Smith, 'Manufacture and Proof of Gunpowder' (London : 1870); Govern ment Report on Explosive Substances (London : 1874); G. 11i. Mowbray, Tri-nitro-glycerine' (New York : 1874); W. N. Hill, 'Notes on Explosive Agents ' (Boston ; 1875); G. G. Andrd, Rock Blasting' (London: 1878); E. Desortiaux, Traite sur la Poudre (Paris: 1878). E. S.