34 TOWERS AND TANKS FOR WATER-WORKS. 



alloys, is exactly opposite to that produced by excess quanti- 

 ties of sulphur, in that it makes the finished product "cold 

 short," crystalline in appearance, of uncertain strength, and 

 liable to fracture from sudden shock. 



That the character or arrangement of the piles has a direct 

 relation to the strength of the product is explained by Camp- 

 bell as follows: " If the piles were square and were made up 

 of similar pieces of equal length, each layer being at right 

 angles to the one below, and if the bloom were rolled equally 

 in each direction, it is evident that the plate would be as 

 strong in the line of its length as of its breadth ; but as the 

 bars from which the pile is formed have been made by stretch- 

 ing the material in one way, and as all practical work requires 

 a piece of greater length than width, it will be seen that the 

 finished product will show much better results when tested in 

 the direction of its length than its width. The result will 

 also depend upon the skill with which the pile has been con- 

 structed ; upon the perfection of the welding as influenced by 

 the heating and the rapidity of handling, and upon the free- 

 dom of the iron from thick layers of slag." 



To secure a pure, refined iron, such as should be specified 

 for structural work, it is necessary, first, to require that the 

 chemical components of the crude iron shall be such as 

 under favorable treatment shall give the desired chemical 

 product; secondly, the production of the muck-bar in suitable 

 condition being largely dependent upon the skill of the work- 

 men, other things being equal, preference should be given the 

 product of old and reputable establishments, and this applies 

 with equal force to the finished product, for it is customary in 

 the manufacture of finished iron to utilize large quantities of 

 miscellaneous " scrap iron/' purchased in the open market, 

 and this scrap, without any careful or intelligent assortment, 

 is piled with the sheared muck-bar until the proper size and 

 weight bloom are obtained, when it is heated to a welding 



