Show 4 civilli civilization aaion ii has as had a d its ages of stone and bronze and steel of wind and water and steam power it re quires taking no great liberties terms to call this an age of edolo oves man blasts out the route for u highway makes it smooth with stone and cement blown out elsewhere and all that it may be traversed by roll mil lions of vehicles propelled by alons of gases overhead airplanes whir driven by explosive engines llan alan has conquered the air only since the harnessing of explosions for or power and has never made a practical flying machine driven by any other form of energy by the roadside farmers plow their fields with tractors driven by similar engines and blast bo bowl ders and stumps from their fields with charges of 0 high explosives s in cities our water supplies come through ii aqueducts que ducts and tunnels that explosives have helped to build dies sel engines driven by exploding pe are replacing steam engines in factories and ships and some light and power plants are operated by these highly concentrated and eco comical mechanisms even steam plants and railways are dependent on explosives for the coot coal which drives them Is torn by powder and dynamite from the bowels of the earth never since man developed his first crude tools wooden clubs stone hammers and the rest has he come upon a device or a substance comparable 1 in force to explosives they give him the powers of a demigod with them he be can come closer to imitating natures forces than in any other wily way explosives depend for their great power on the fact that while occupying a relatively small sp space ace an in amant before explosion their gases occupy a tremendously greater space the instant after gunpowder the first and the lamest ot of the well known explosives exerts when it explodes in a confined space times the pressure of the atmosphere or nearly dearly CO W tons per square inch the high explosives dynamite gun cot ton nitroglycerin and TNT exert several times the force of powder and mercury fulminate the most violent of all produces a pressure of tons per square inch the latter finds find its chief use la in very small quantities to in the form of caps used to detonate less violent explosives most sensitive explosive all explosives are dangerous and must be handled with caution but there are definite degrees of dangerousness ous ness gunpowder and dynamite will not explode unless subjected to a more or less violent jolt altro glycerin and TNT are detonated much more easily the most sensitive of nil all explosives Is nitrogen iodide this sub stance Is so unstable that it Is said that the tap of a feather will set it off even in peace time the united states manufactures large quantities of explosives in 1925 1025 the total not considering explosives tor for amount ammunition was more than halt half a billion pounds of this approximately two thirds was made up of high explosives and one third of black powder A quarter of the high explosives and SO 86 per cent of the black powder was used in coal mining nearly half of all the high explosives were used in metal mining and quarrying and the remaining quarter was divided about equally between construction work and miscellaneous uses many absorbingly interesting ices to nian man are hidden behind the miscellaneous classification explosives are used among other ways in channel deepening to produce echo waves in the scientific divining rods of the oil prospector to aid in drain ing swamps to blow up levees tor for emergency flood protection to tight light great fires to destroy the bodies of dead animals to shoot oil wells to send up signal rockets and fireworks to cast life lines to ships in distress to break up lee ice jams log jams and icebergs and to prepare holes for the planting of trees mans discovery ot of explosives la Is not definitely known records do riot not bear out the widely held opinion that the chinese invented gunpowder pyrotechnic substances such as greeli greek fire or wild fire were used in the early and middle centuries of the christian era to frighten enemies or to set fire to their ships but one of the first definite tilte recipes tor for gunpowder appears in the writings of roger bacon in the thirteenth century the first drat recorded use ose to propel missiles from cannons was to in florence in 1329 1320 the beet army worm and several forms of web worm damage the beet they may be controlled by use of ar senate of lead 0 0 heavy seeding needing of barley on fertile tolla bolls Is not ended the bt rate Is from one and one half to oni and three quarters bu bus liola sin an acre 0 0 keep ull all weeds from the asparagus plantation and conserve moisture for the use of the Til klints lints by cultivating thoroughly tit at least once a week nil through the SUI |