ELASTICITY 



1975 



ELBURZ 



being exterminated. A larger species is found 

 in Western Africa. For illustration, see page 

 278. 



ELASTICITY, elastis'iti, a term used in 

 physics to designate that property by which 

 bodies resume their original size and form 

 when the external force by which their size 

 and form have been changed is removed. All 

 substances possess this property in some degree. 

 Elasticity is of two kinds, elasticity of volume, 

 which is the property of gases and liquids, and 

 elasticity of form, the property of solids. Solids 

 that have little ability to resume their original 

 shape after the action of stress or pressure are 

 said to be inelastic, or plastic. When a body 

 has reached its elastic limit, further stress or 

 pressure will cause permanent change of form 

 or size. This is illustrated by a rubber band 

 which has been stretched until it will not 

 resume its original size. Elasticity may be 

 developed by pressure, pulling, bending or 

 twisting. Gases are the most elastic substances. 

 Hard solids are more elastic than soft solids. 

 Such substances as lead, putty and dough have 

 very little elasticity. See PHYSICS; MATTER. 



EL'BA, an Italian island in the Mediter- 

 ranean Sea, six miles west of the mainland, 

 historically famous as the enforced residence of 

 Napoleon Bonaparte after his first abdication 

 in 1814. Here he remained, with supreme 

 authority, until 1815, when followed the famous 

 "Hundred Days" in European history, March 

 20 to June 28, from the date of his entry into 

 Paris to the second abdication. The island is 

 eighteen miles in length and three miles in 

 width, and is mountainous in character. Its 

 principal product is iron, but it is also rich in 

 marble, wines and fruits. The sardine industry 

 gives employment to a part of its inhabitants. 

 It has two well-fortified seaports, as fortifica- 

 tions were understood before the War of the 

 Nations; these are Porto Ferrajo, the capital, 

 and Porto Longone. For governmental pur- 

 poses it is a part of the Italian province of 

 Leghorn. Its population is about 26,000. 



EL 'BE, a German river which is one of the 

 most important commercial highways of Cen- 

 tral Europe. It rises on the borders of Bo- 

 hemia and Silesia, at an altitude of 4,000 feet, 

 and after a course of 780 miles empties into the 

 North Sea, at the port of Cuxhaven. Wherever 

 possible the Elbe has been rendered navigable, 

 and towns on its banks have vied with each 

 other in building docks with improved loading, 

 unloading and storage facilities. Dresden, Wit- 

 tenberg, Magdeburg, Torgau and Hamburg are 



the most important commercial centers passed 

 in its course, and each city takes the fullest 

 advantage of the cheap transportation and 

 water power it affords. 



Steamers and barges navigating the Elbe out- 

 number those of any other German river. 



COURSE OF THE ELBE RIVKU 



Ocean-going vessels ascend as far as Hamburg, 

 eighty miles from the sea. The fisheries are 

 valuable sturgeon, shad and salmon being 

 taken in great numbers. Vast quantities of tim- 

 ber are floated down the Elbe from the interior 

 to the sea. A network of canals connects the 

 river with the commercial centers of the sur- 

 rounding territory, and in this way its advan- 

 tages have been developed probably more than 

 those of any other river in the world. 



ELBERFELD, el her felt', an important 

 commercial town of Germany, forming practi- 

 cally one city with Barmen, although they arc 

 municipally separate. It is situated on both 

 banks of the River Wupper, about fifteen milca 

 northeast of Diisseldorf. Klberfeld has long 

 been a noted educational center, and it i> only 

 within recent years that it has assumed com- 

 mercial importance. It is now the center of 

 German cotton, wool, velvet and silk imlu.-trn-v 

 and produces great quantities of <-hrmir;ils and 

 dyestuffs. Extensive foroign and domestic 

 trade is carried on, and the city has excellent 

 railway communications with interior and coast 

 towns. Klberfeld owes ill original industrial 

 growth to Napoleon's continental xystetu 

 (which see), which prohibited all dealings with 

 the British. Population in 1910, 170,118. 



ELBURZ. el boorz' , a chain of mountains in 

 Northern Persia, extending from the western 



