Explosions by Influence.— In detonating explosive substances it has been found that the influence of the detonation is exerted to a dis tance all about the mass depending on the kind and the amount of the explosive used and its environment and that a second charge of ex plosive within the sphere of influence may be detonated by the detonation of the first charge without being in contact with it. Thus in acci dental explosions in explosive works the initial explosion occurring in one building may de tonate the explosives in other buildings unless care is taken in the construction of the works to separate the buildings by a safe distance from one another. Care, too, must be taken in forming fixed ammunition that the primers are not heavily charged with fulminate, and that the cartridge's are so packed that the accidental explosion of one cannot explode the others by influence. Application of this principle is made in military engineering in the operation of countermining, the enemy's submarine mines be ing blown up by firing a heavy torpedo charged with guncotton in the vicinity of them. To-day large quantities of explosives are frequently used in big blasts. According to Eissler, it is an almost daily occurrence in California for 20,000, 30,000 and even 50,000 pounds of explosives to be used in a single charge. The system of large blasts has even become common in hard rock excavations, such as quarries and railroad cut tings, and in these large blasts it is common practice to dispose the larger part of the mass of explosive so that it may be exploded by influ ence and not by contact or by propagation of flame or fire.
The largest single blast ever fired was that used in the blowing up of Flood Rock at Hell Gate in the East River, N. Y., 10 Oct. 1885. There was used in the blast 240,399 pounds of rackarock and 42,331 pounds of dynamite, or 283,000 pounds of explosive. There were 13,000 separate charges of rackarock embedded in drill holes with a dynamite cartridge on top of each, and there were 591 primary charges of dynamite placed on timbers 25 feet apart within the mine. When all the charges had been placed in the excavation and the primary charges connected with the firing batteries, the mine was filled with water, the primary charges were exploded by the electric current and these exploded the 13,000 other charges by influence through the intervening water. Munroe founded on this principle a method of testing the relative sen sitiveness of explosive substances.
Uses of Explosives,- The uses of explo sives as propellents in war and in the chase; as rupturing agents in mining, quarrying and engi neering operations, and as an essential compo nent of fireworks is well known. It is not so generally known that they are employed for sav ing life and property in signal lights, rockets and guns; in projecting lines from the shore to stranded ships, and, in case of fire, to the upper stories of high buildings; in casting oil upon the water to quell a raging sea; and in railroad torpedoes to prevent collisions. Gunpowder
guns are also used in bridge building to project a line across a chasm which is to be bridged, and they are used in the whale fishery to project the harpoons, while the latter may carry an ex plosive charge with which to stun or destroy the whale. Detonating explosives have been im properly used in taking fish; in burglarious operations against safes and vaults and in anarchistic outrages. Dynamite has been used to knock the blocking from the ways when launching ships. Fired on an iron plate placed on the top of a pile and covered with a tamping of earth or clay, it has successfully replaced the pile driver. It has been found efficient in ex cavating holes in which to plant telegraph and telephone poles and fence posts; in driving water out of quicksands in which foundations are to be laid or shafts to be driven; in slaugh tering cattle; in breaking down ice dams to pre vent inundations; in blowing up buildings to prevent the spread of conflagrations; in razing unsafe walls of burned buildings; in destroy ing wrecks which endanger navigation, and in freeing vessels which are hard aground on shoals. The farmer uses them in breaking boulders, grubbing stumps and felling trees; in shaking the soil to fit it for deep-soil culti vation, and, in wine growing districts, to free the soils from the phylloxera: while their aid has been sought in breaking droughts and diverting hailstorms from their courses. The iron founder uses them in breaking large cast ings. The iron smelter employs them to clear out obstructions in blast furnaces while the lat ter are still in operation. Munroe proposed using detonating explosives as a means of test ing the integrity of large masses of metal and their resistance to shock.
Transportation of Explosives.— It is well known that the transportation of explosives is a necessary menace. Munroe pointed out that in 1904 there was not less than 600 cars of ex plosives on the railroads of the United States each day. In 1905 the matter of regulating the transportation of these and other dangerous substances was taken up by the American Rail way Association and a bureau of supervision was created. Later the matter was taken up by the United States Congress and by its acts of 4 March 1909 and 18 June 1910, this super vision and regulation was entrusted to the In terstate Commerce Commission which, on 2 July 1914, issued a pamphlet of 196 pages con taining its regulations for the safe transporta tion of explosives, inflammables and other dangerous substances, and these now control.