EXPLOSIVES LAW 



3053 



EXPRESSION 





Dynamite, gelatine dynamite, 

 and blasting gelatine are generally 

 used where great shattering effect 

 is required, and gunpowder is still 

 employed for rending. Military 

 requirements generally demand a 

 most brisant effect from shell fil- 

 lings, and here nitro- aromatic com- 

 pounds alone are most used, 

 trinitrotoluene being pre-eminent ; 

 but during the Great War shortage 

 of supplies rendered it necessary to 

 employ ammonium nitrate explo- 

 sives for this purpose, and amatol 

 and schneiderite are examples of 

 successful practice. Smokeless 

 powders all have nitrocellulose as 

 a basis, and some contain nitro- 

 glycerine in addition (see Cordite, 

 Poudre B., Ballistite, E.G. Powder, 

 Schultze Powder, etc.) propel- 

 lants for rifled weapons being re- 

 quired to burn much more slowly 

 than for smooth bores. 



Combustion, explosion, and de- 

 tonation are terms designating the 

 same chemical change, the sole 

 variant being the speed with which 

 reaction occurs, detonation being 

 so rapid that an explosive wave 

 apparently propagates the change 

 instantaneously through the whole 

 mass, whereas in combustion and 

 explosion the reaction proceeds 

 by layers through each particle. 

 Use in Mining 



In mining, explosives are used to 

 supplement the work of the miner's 

 pick in breaking down the rock 

 which it is desired to remove. The 

 explosives in common use com- 

 prise: gunpowder; cheddites, which 

 are chlorate preparations ; dyna- 

 mite, blasting gelatine, gelignite, 

 Ardeer powder, britonite, cam- 

 brite, arkite, carbonite, kolax 

 and duxite, which are preparations 

 of nitroglycerine ; ammonite, 

 bellite, Faversham powder and 

 roburite, which are preparations of 

 ammonium nitrate, and fulminate 

 of mercury, which is used for de- 

 tonators. Gunpowder is still large- 

 ly used, especially for the softer 

 rocks, on account of its cheapness 

 and general security. The dyna- 

 mites, blasting gelatine, and gelig- 

 nite are most used for hard rocks 

 where an intense shattering effect 

 is desired. 



For use in coal mines, particu- 

 larly those where there is a risk 

 of a gas or coal-dust explosion, 

 safety explosives are employed, 

 these usually having an ammonium 

 nitrate base, sensitised with either 

 nitroglycerine or an aromatic nitro- 

 compound. Explosives of a similar 

 type, but of a more brisant nature, 

 including some of the cheddites, 

 ammonals, etc., are used in mining 

 and quarrying. For military de- 

 molitions guncotton or trinitro- 

 toluene is usually employed, but 



dynamite or blasting gelatine may 

 be used in an emergency. For 

 land mines the British army used 

 ammonal extensively during the 

 Great War. See illus. p. 2346. 



Bibliography. ExplosiveMaterials, 

 M. P. E. Berthelot, Eng. trans. M. 

 Benjamin, 1883 ; Traite theorique 

 et pratique des explosifs modernes, 

 P. F. Chalon, 2nd ed. 1889 ; Manu- 

 facture of Explosives, O. Guttman, 

 1895 ; with supplement, 1909 ; 

 Poudres et Explosifs : dictionnaire 

 des matieres explosives, J. Daniel, 

 1902 ; Explosives, H. Brunswig, 

 Eng. trans. C. E. Monroe and A. L. 

 Kibler, 1912; Les Poudres et 

 Explosifs, L. Vennin and G. 

 Chesneau, 1914 ; Explosives, A. 

 Marshall, 2nd ed. 1917 ; Notes on 

 Military Explosives, E. M. Weaver, 

 4th ed. 1917 ; High Explosives, 

 E. de W. S. Colver, 1918. 



Explosives Law. A new Act 

 concerning explosives was passed 

 in England in 1860, and amended 

 in 1861 and 1862, repealing all 

 previous Acts. In 1875 a new Ex- 

 plosives Act was passed dealing 

 comprehensively with the whole 

 question. This was based on the 

 report of the House of Commons 

 Committee appointed to enquire 

 into the terrible explosion on the 

 Regent's Canal in 1874, and still 

 governs the whole question. Part I 

 deals with gunpowder, which may 

 only be manufactured in licensed 

 factories and kept in licensed maga- 

 zines under specified conditions. 

 Part II deals similarly with nitro- 

 glycerine, and other high explo- 

 sives ; Part III with inspection, 

 accidents, search, etc., and Part IV 

 gives supplementary provisions. 

 The Act is administered by the 

 home office, which publishes 

 annual reports of its inspectors, 

 and is responsible for new regu- 

 lations, etc. The term explo- 

 sive may include any substance 

 deemed to be specially dangerous, 

 and the Act provides for the com- 

 position, quality, character, and 

 classification of any explosive to 

 be defined by an Order in Council. 

 Owing to many of the newer ex- 

 plosives being of a poisonous 

 nature, regulations can also be 

 made to safeguard the health of 

 workers. Most other countries 

 have introduced similar legislation. 

 The Merchant Shipping Act of 

 1894 regulates the carrying of 

 explosives in British vessels. 



Exponent (Lat. ex, from, out ; 

 ponere, to place). Symbol of an 

 algebraic expression denoting the 

 number of times the expression is 

 to be multiplied by itself. Thus in 

 the expression a 3 , the figure 3 is the 

 exponent of a, and the expression 

 is equivalent to a times a times a. 



Exponential. A term used 

 in mathematics. The exponential 

 function is the inverse of the loga- 



rithm : thus if y=log x, then x is 

 said to be the exponential of y. 

 See Logarithms. 



Exports (Lat. exportare, to 

 carry out). Name given to goods 

 sent out of a country. These are 

 valued at the custom houses, or by 

 other authorities, and all civilized 

 countries issue periodical returns 

 showing their value. In the United 

 Kingdom this is done monthly by 

 the board of trade. They are divid- 

 ed into four main classes : food, 

 drink and tobacco ; raw materials ; 

 manufactured articles ; miscella- 

 neous. The total value of a year's 

 exports from the United Kingdom 

 rose from 354,400,000 in 1900 to 

 962,694,911 in 1919, but this great 

 increase was largely due to an ad- 

 vance in prices, not to an advance 

 in volume. 



The difference between a coun- 

 try's exports and its imports is 

 known as its balance of trade, but 

 to strike an accurate balance cer- 

 tain considerations should be re- 

 membered. For instance, exports 

 are valued at their price when put 

 on board ship, whereas in the price 

 of imports the cost of carriage is in- 

 cluded. Invisible exports is the 

 name given to charges for freights 

 and the like. These are paid to the 

 country owning the carrying ships 

 and play a part in the balance of 

 trade, but are not included in the 

 monthly figures. See Balance of 

 Trade; Trade. 



Exposition (Lat. exponere, to 

 set forth). In music, the placing 

 out or setting forth of the themes 

 and materials upon which a piece is 

 constructed. In fugue the exposi- 

 tion includes the first entries of all 

 the voices or parts. In sonata form 

 it includes the first presentation of 

 the chief themes, before their deve- 

 lopment or elaboration is entered 

 upon. See Fugue ; Sonata. 



Express. Literally to press out, 

 a word used in several senses, all, 

 however, conveying the idea of 

 speed. It is given to a fast train 

 and to a newspaper. See Railways. 



Expression, FACIAL. Outward 

 indication on the features of the 

 inward character or emotions. Sir 

 Charles Bell first put the matter on 

 a scientific basis in his essay on the 

 Anatomy of Expression in Painting, 

 1806. Continental writers fol- 

 lowed, but the great classic work on 

 the subject is Charles Darwin's 

 Expression of the Emotions in Man 

 and Animals, 1872, in which are 

 set forth the physiological reasons 

 for the variety of expression of 

 which the human face, and in a 

 lesser degree the faces of animals, 

 are capable. 



Darwin maintains that some hu- 

 man expressions, such as the bristl- 

 ing of the hair under the influence 



