EXPLOSION 



Livingstone, Stanley, Manning, 

 Speke, and others among English- 

 men, and of a number of French- 

 men and Germans. The secrets of 

 the Nile and the Congo were re- 

 vealed, and soon there was little 

 for the explorer to do. 



From the time of the discovery of 

 America, explorers had turned their 

 attention to a north-west or 

 north-east passage, and from this 

 came the desire to reach the north 

 pole. The south pole, too, was 

 aimed at, and the exploration of 

 the world's surface may be said to 

 have ended whsn these goals were 

 reached. See Africa ; Antarctic 

 Exploration; Arctic Exploration; 

 Australia. 



Explosion (Lat. ex, from, out; 

 plaudere, to clap). Accidental igni- 

 tion of gas. Explosions in coal mines 

 are due to the fact that coal de- 

 posits are liable to give off certain 

 gases which, when mixed with air in 

 certain proportions, form explosive 

 compounds which only require a 

 spark or flash to fire them with 

 possibly disastrous consequences to 

 the workers, as at Courrieres in 

 France in 1906, when 1,100 lives 

 were lost. Not all coal mines are 

 equally liable to have explosions ; 

 many, indeed, are so entirely free 

 from fire-damp that naked lights 

 are used by the miners in all parts 

 of the workings, while electricity 

 is freely employed both for lighting 

 and for power purposes. In others 

 the danger is always present, and 

 the most exacting precautions are 

 necessary to avoid a disaster. 



It is, indeed, contended by many 

 authorities that no coal mine can 

 be absolutely safe, as dust alone 

 without any admixture with me- 

 thane or fire-damp may give rise 

 to an explosion. The flame from a 

 blown-out shot, that is from an 

 explosive cartridge which has not 

 expended its force upon the coal 

 in which it has been embedded, but 

 has blown out the tamping by 

 which it was shut in, may be 20 ft. 

 in length and even 35 ft. in narrow 

 galleries, and may travel 80 ft. or 

 more along the workings if dust 

 be present in the air ; consequently 

 a real danger may exist even in 

 mines which are not " fiery." 



Apart from blown-out shots, 

 which are regular occurrences, an 

 explosion may be caused by any 

 kind of spark or flame or any 

 ignited substance a blown electric 

 fuse, a broken electric lamp, for 

 example, where electricity is em- 

 ployed ; or an overheated safety 

 lamp. It is a remarkable circum- 

 stance that mine explosions began 

 to be more frequent as the ventila- 

 tion of the workings was improved, 

 a circumstance which led to an im- 

 portant inquiry as to the relations 



3051 



between explosive gas and the oxy- 

 gen in the atmosphere of the work- 

 ings. Legislation in this country re- 

 quires that the oxygen in the air 

 of the workings shall not be below 

 19 p.c. and that the carbonic acid 

 gas shall not exceed a definite very 

 low proportion, but inquiry has 

 shown that an explosion would be 

 almost impossible if the proportion 

 of oxygen were reduced to 17 p.c. 



Thus the measures taken on the 

 one hand to improve the working 

 conditions of the miners would 

 appear only to increase his risk in 

 another direction. Other precau- 

 tions recommended to prevent an 

 explosion comprise watering the 

 dust of the floor at the working face 

 before firing a shot ; removing the 

 dust from the intake haulage ways 

 by reversing the air current from 

 time to time ; watering the floor, 

 sides, and roof of the roadways, and 

 rendering the coal-dust unignitable 

 by mixing it or covering it with 



EXPLOSIVES 



stone-dust, which may be made by 

 grinding waste shale, '^he use of 

 safety-lamps (q.v. ) is made impera- 

 tive and certain classes of explo- 

 sives prohibited by legislation in 

 all dangerous mines ; while arrange- 

 ments now exist for giving all coal 

 mining regions warnings of any 

 approaching atmospheric changes 

 which may be calculated to favour 

 the escape of gas in the workings 

 and thus increase the normal risks. 

 Where risk of explosion is the 

 normal condition of a mine, special 

 preparations are now made at the 

 most modern works for the prompt 

 release of miners who happen to be 

 below at the time of the explosion. 

 These men may escape with their 

 lives from the explosion itself only 

 to fall victims to the after-damp or 

 choke-damp, unless they can be 

 promptly got out, and as a rule 

 their ways of escape will be blocked 

 by destroyed or damaged workings. 

 See Coal-dust; Fire-damp. 



EXPLOSIVES: IN PEACE AND WAR 



Capt. E. de W. S. Colver, Author of High Explosives 



In addition to the following introductory sketch this work contains 

 shorter articles on all the leading explosives, e.g. Dynamite ; Gun- 

 powder, etc. See also A vnmunition ; A rtillery ; Gas, etc. 



Explosives (Lat. explosus, driven 

 out) are solid or liquid substances or 

 mixtures which are capable, when 

 suitably initiated, of being conver- 

 ted in a very small interval of time 

 into other more stable substances 

 which are wholly or chiefly gaseous. 



Contrary to popular belief, the 

 energy content of explosives is 

 comparatively low, as shown by 

 the relative heat (energy) content 

 of the following: petroleum, 15; 

 coal, 10 ; wood, 5 ; nitroglycerine, 

 2. The tremendous explosive effect 

 is solely due to their capability of 

 releasing the whole of their energy 

 in a minute interval of time. 



The early history of explosives 

 and their actual invention is a 

 matter of much speculation. Gun- 

 powder is certainly the oldest 

 variety, and whilst many writers 

 confer on it great antiquity and 

 connect it with " Greek fire," it is 

 doubtful whether saltpetre of 

 sufficient purity was known at the 

 time. Saltpetre was known to the 

 Chinese and Arabic people about 

 1200, and they used it in fire- 

 works for military purposes. Roger 

 Bacon' s writings contain undoubted 

 references to gunpowder, instruc- 

 tions for its manufacture being con- 

 cealed by cyphers, and he was well 

 acquainted with the fact that it 

 explodes violently when ignited in 

 confinement. No real development 

 of gunpowder occurred until it was 

 used for the propulsion of missiles 

 from guns, and this invention 

 appears to be due to a German 



monk, Berthold Schwartz. Old 

 manuscripts record different dates 

 for the discovery, but guns were 

 certainly in use by 1320. 



For some six centuries gun- 

 powder remained the only explo- 

 sive known to man, and its compo- 

 sition remained almost unchanged, 

 saltpetre, charcoal, and sulphur 

 being the ingredients, in varied 

 proportions. Its progress from an 

 uncertain, irregular medium to a 

 uniform and reliable explosive 

 has been entirely due to im- 

 proved manufacturing methods and 

 greater purity of ingredients, this 

 tending to more intimate contact 

 of the components and conse- 

 quently to faster and more regular 

 burning. A mechanical mixture of 

 oxidiser and combustible can never 

 exceed a certain degree of intimacy 

 of contact, so the rate of burning 

 or violence of explosives was limited 

 whilst gunpowder remained the 

 only type. 



Marked progress was made after 

 1846, when both nitrocellulose 

 and nitroglycerine were dis- 

 covered, the former simultaneously 

 by two Germans, Schonbein and 

 Bottcher, and the latter by an 

 Italian, Sobrero. Both proved to be 

 extremely violent explosives, in- 

 comparably more powerful than 

 gunpowder. The reason for this is 

 that both are chemical compounds, 

 the oxidiser and combustible being 

 combined in the same molecule, 

 and hence in the closest possible 

 contact. They are types of a 



