EXPOSITION 



2115 



are directly or indirectly derived from nitric 

 acid, one of the principal constituents of the 

 saltpeter used in the original gunpowder. In 

 general, the chemical compounds used as ex- 

 plosives are made by the action of a mixture 

 of nitric and sulphuric acids upon non-ex- 

 plosive compounds' thus: picric acid is pro- 

 duced from carbolic acid; nitroglycerine from 

 glycerine ; guncotton from cellulose (cotton) ; 

 trinitrotoluene from toluene. 



Picric acid, also a product of nitric acid, is 

 used as an explosive in the lyddite shells of 

 the British army, and is deadly not only from 

 the force of the explosion but on account of 

 the fumes of the gases formed. Melinite, used 

 by the French, is much the same in composi- 

 tion and effect. Trinitrotoluene is also much 

 used as a high explosive for charging shells. 

 Many experiments have been conducted in 

 Germany with the- object of producing explo- 

 sives of greater power, but so far as is known 

 nothing has been discovered to supersede gun- 

 cotton and nitroglycerine. It is said that dur- 

 ing the War of the Nations, before the end of 

 1915, the Germans were compelled by shortage 

 of cotton to resort to wood pulp for the pro- 

 duction of such explosives as had been pre- 

 viously dependent on guncotton. In that, how- 

 ever, they had been long anticipated, as Nobel 

 m 1866 had used both wood pulp and fiber as 

 a base for dynamite. 



The manufacture of explosives is attended 

 with considerable danger. In those consisting 

 of chemical compounds the greatest care is 

 necessary, especially in the preparation of the 

 materials. For commercial purposes explosives 

 are put up in various ways, the object being 

 to render them as safe as possible to handle. 

 Dynamite and blasting gelatin, with an average 

 of more than thirteen times the power of gun- 

 powder, are .put up in "sticks" covered with 

 paper. The sticks are usually about one inch 

 in thickness and eight inches in length. The 

 amount of dynamite used in blasts varies from 

 half a stick to several thousands of pounds, 

 according to the nature of the operations. 



Related Subjects. The reader is referred to 

 the following articles in these volumes, and to 



ich other references as they suggest : 

 Ammunition Guncotton 



Artillery Gunpowder 



Carbolic Acid Nitroglycerine 



Dynamite Pi cric Acid 



EXPOSITION, cks po zish'un, INDUSTRIAL, 

 an exhibition of large numbers of the products' 

 of industry and art. The great international 

 expositions of the present decade, with thou- 



EXPOSITION 



sands of exhibits from all parts of the world, 

 are an outgrowth of the small local fairs which 

 were common in Europe in the Middle Ages. 

 These fairs were the earliest industrial exhibi- 

 tions; the workers brought the products of 

 their yearly or half-yearly labor to the markets 

 for display and sale. Such gatherings seem 

 originally to have had a religious character, 

 but this was soon subordinated to the com- 

 mercial. The fair at Saint Denis was held for 

 the first time in A.D. 620, and that at Aix-la- 

 Chapelle about 800. Such fairs are still com- 

 mon in various sections of Europe, but the 

 most famous are those of Leipzig, especially 

 for the trade in furs and books. The great 

 fair at Nizhni Novgorod, held each year in 

 July and August, is a notable event in the 

 Russian Empire. 



The modern industrial expositions have for 

 their chief object the advertisement of prod- 

 ucts with a view to the ultimate increase in 

 sales. Industrially, the modern exposition is 

 a series of great sample-rooms, but along with 

 the industrial features have developed other 

 elements not of business character. Exposi- 

 tions now include displays of the fine arts, of 

 educational material and of many things which 

 are not intended to be sold. Above all, the 

 visitors must be amused, and the so-called 

 "concessions," or amusement stands, are now 

 prominent features of all such enterprises. 

 Most of the people who now visit expositions 

 go not only as a matter of business, but "they 

 expect entertainment, as well. 



Along with the attention to pleasure has 

 come increasing regard for the architectural 

 and landscape possibilities of a great exposi- 

 tion. The earliest buildings, like the Crystal 

 Palace in London, were ugly structures of iron 

 and glass. The buildings of the Centennial 

 Exposition at Philadelphia were chiefly of 

 iron, timber and glass. The first buildings of 

 an entirely new kind were erected in Chicago 

 for the World's Columbian Exposition in 1893. 

 The framework was of timber and iron, but 

 the exterior was a material called staff, a 

 preparation composed largely of plaster of 

 Paris. Being easily molded, this material 

 permits artistic effects at small cost. The 

 buildings are given a festive character, and the 

 entire grounds have the appearance of a vast 

 pleasure resort. Compared with wood or stone 

 construction, staff is very cheap, but the ma- 

 terial is perishable. In a few months, or at 

 most a year, it cracks and begins to fall to 

 pieces. Staff, however, serves all exhibition 



