Blashfield, Edwin

HOW LAND, b. at New York, Dec. 15, 1848; a subject painter. Author of A Poet; Toreador; The Augur; Emperor Commodus Leaving the Amphi theatre at the Head of the Gladiators; The Fencing Le on; The Besieged; a number of decorative panels; a portrait of H. McK. Twombley, . Blasting. ( Mining and Quarrying .) The compounds of nitro-glycerine, so strongly objected to for some years, have now come to the front as the safest as well as the most powerful of explosives. Nitro-glycerine or nitrate of glycerine, was discovered in 1847 by the Italian chemist, Sombrero. It is a pale-yellow, oily fluid, of 1-6 sp. gr., which commences to stiffen and solidify when the temperature falls below 8° C., or 47° F. It is insoluble in water, but can be mixed with methylated spirit, benzole, nitro-benzole, or a mixture of alcohol and ether. Against the use of pure nitro-glycerine a strong prejudice still exists in consequence partly of the poisonous nature of the substance, but mainly on account of its violent and sensitive nature, and the many accidents which happened in its earlier applications. Nobel, the Swedish chemist, was the first to tame its violence, and to put it under complete control, so far as safety was concerned, by mixing it with the fine infusorial earth so well known to microscopists, and thus forming a simple mechanically plastic substance, handier as well as safer for use for mining and quarrying purposes. This substance, consisting of 75 per cent. of nitro-glycerine and 25 per cent of silicious meal, was proved, both as to safety and power, by numerous most important and convincing experiments, and has reached an enormous sale for blasting operations under the name of dynamite. Thus compounded the plastic ma is of a tawny reddish hue, of a consistency approaching that of putty. Set on fire in the open air, dynamite merely deflagrates; it will simply burn when enclosed in ordinary boxes, producing only slightly noxious gases and very little or no smoke. It explodes only in completely closed spaces, and with difficulty by means of sparks. It may be, when thus confined, exploded by glowing hot metals, by bullets fired into it, and otherwise by deliberate artificial ignition. The disadvantage urged against it in its practical application is, that when the temperature falls below 6o C., it hardens, and that then, particularly when loose cartridges or a series of cartridges are employed, the whole of the charge is not exploded, but a portion remains altogether undamaged, or is blown out unexploded. The cause of this stiffening is of course due to the natural crystallization of the nitro-glycerine. Litho fract eur , the invention of Prof. Engels, is an improvement upon dynamite, and derives its advantages from the diminution of the proportion of silicious meal as well as of the nitro-glycerine, the balance being made good by other ingredients of an explosive nature. It also is produced in a plastic state, being black in color and doughy in consistency. When lit by a match or a cigar, like dynamite, it merely burns; but it is almost insensible to blows or pre ure, and can only be exploded by a strong priming cap or detonator composed of the strongest fulminate. Attempts to explode it by charges of gunpowder have failed. How little sensitive it is to violent shocks has been shown by throwing it over cliffs of 150 ft. or 200 ft. in height; as also by firing shells fitted with it from cannon, which exploded only when they reached some hard object of stone or iron. Neither in combustion nor explosion does it generate smoke like gunpowder; but the gases formed are transparent, and only detectable by the smell. Other forms of dynamite are largely in use, known by the various titles of Atlas, Dualine, For cite, Tonite, Rendrock, Hercules, Rack a rock, and Vulcanite. For mining purposes the great desideratum is the quantity and nature of the work done by the explosive, for the main expense in such work is the cost of boring holes for the charges. If, then, these can be diminished in number as well as in dimensions by the greater power of the blasting material, the saving in the quarrying or mining operation becomes far more important than the difference in cost between the cheaper and le effective blasting-powder and the nitro-glycerine compounds, although that difference in price may be considerable, pound for pound. The difference in the price of the powder is also more than equalled in the saving of human labor in drilling the holes; and it is generally a umed that this gain alone deducts a third from the expense which the manual labor required for blasting-powder entails. The method now generally employed in blasting operations is to use the cartridge, from which projects the copper "priming needle." A very soft clay material called tamping is used to fill the hole above the powder and around the needle, it being rammed gas-tight by a copper-tipped "tamping bar." After the needle has been withdrawn a fuse is inserted, which, when ignited, fires down into the powder. Dynamite is charged in cartridges with a safety fuse, or electric wire and cap, slightly tamped. All high explosives are now fired by the aid of strong detonators, several charges being generally prepared and fired simultaneously. This can be properly done only by electricity. The different holes are connected in series by a conducting wire, through which a current of electricity is sent from a small hand-power dynamo, or a frictional machine. Steam drilling has now, in a considerable measure, replaced the slow and expensive hand-drilling proce , and great improvements have been made in the working power of drills, so that the cost of drilling operations has been greatly reduced, and the rapidity as largely increased. The diamond drill has been employed to a considerable extent in prospecting, though it has not come into use in mining and tunneling for the drilling of blasting holes. As an example of the rending power of the new explosives, we may quote the following experiments: A piece of cast-metal 9 ft. long, 6 ft. wide, and 17 in. thick, was broken into three large, and many small pieces, and a second, 12,000 lbs. in weight, was shattered into four pieces. Over each block fifteen rails were laid, in order to protect the neighboring houses. "These rails were hurled about 300 feet up into the air, in many little pieces, affording a diverting spectacle. The charge is not recorded, but at an E en experiment a block of cast-iron, 53 in. long, 29 in. broad, and 18 in. thick, was split through at a single discharge by about 6 lbs. of litho fract eur, simply laid on the smooth surface and tamped with a few handfuls of loam.