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Engineers, supplies the following reasons why steel made 

 according to Lloyd's requirements is superior to iron for ship- 

 building. 



1st. It is very much more ductile. 



2nd. It is equally ductile in both directions of the grain. 



3rd. It has 30 per cent, more tensile strength in the direc- 

 tion of the grain. 



4th. It has 50 per cent, more across the grain. 



5th. Its elastic limit is 21 per cent, more in either direction 

 of the grain. 



He goes on to point out a curious and important fact, though 

 little known, that the elastic limit in iron plates is equal in 

 both directions, as it is in steel, although the ultimate strength 

 and ductility are inferior in the cross direction. 



It seems clear that mild steel has much less practical advan- 

 tage over wrought iron when used for bridges and roofs than 

 when used for ships. 



STEEL EOR BRIDGES. 



The great advantage gained by the use of steel for bridges 

 and other similar work is its high elastic limit as compared 

 with its weight, and in all large spans this is an important ele- 

 ment, as the weight of the span is the principal cause of the 

 strain, but, notwithstanding this, English engineers are slow 

 to introduce steel very largely into general use, as wrought iron 

 is still more used than steel in bridges and roofs and for agri- 

 cultural implements. 



RAILS, TYRES. 



Closely connected with the use of steel for bridge and roof 

 building is its application to rails, tyres, axles, &c. The use of 

 steel rails is now almost universal, and they can be produced at 

 a lower rate per ton than wrought iron rails. They are usually 

 made by the Bessemer or Siemen's process, and are found to be 

 infinitely superior in wear and tear to wrought iron. They 

 should be tough, and yet not brittle under traffic, and able to 

 stand the breaking and crushing effects produced by the loco- 

 motive wheels. Mr. Price "Williams, a recognised authority, 

 states that a steel rail will outlast nine iron rails under the 

 same conditions of traffic, and it may be accepted as a fact be- 

 yond dispute that it will at least last double the time. 



It is chiefly on account of the great resistance of steel to 

 abrasion that this material has superseded iron for railway wheel 

 tyres, but where such a quality is not absolutely essential, such 

 as in ordinary works where bars, angles, and plates are used, 

 and in bridges, roofs, and ships, iron is as good as steel, and 

 steel is only used in consequence of its superior elastic limit in 

 proportion to its weight. With regard to the application of 



