52 TOWERS AND TANKS FOR WATER-WORK'S. 



ported pipes to have been of most unusual and eccentric de- 

 sign, whilst two pipes collapsed owing to failure of designers 

 to provide plates whose unit stress should be suitable for con- 

 ditions well recognized at this date. Deducting those pipes 

 whose partial or total destruction should have been provided 

 against, there remains only four failures unexplained, and one 

 of these might be placed if the history of the structure were 

 known. 



In view of this testimony and the most conclusive and 

 practical evidence offered by the constant and increasing use 

 of structural steel, there can be no question as to the fitness 

 and adaptability of this product to the many purposes of the 

 mechanical arts. 



Continuing the consideration of this question, an interest- 

 ing discussion upon the choice of materials may be found 

 in Prof. W. D. Pence's "Stand-pipe Accidents and Fail- 

 ures," which, on account of its clearness and propriety, is pre- 

 sented here literally: 



"Relative Merits. In weighing the relative merits of 

 steel and wrought iron as materials for the construction of 

 stand-pipes, it may not be denied that each material has points 

 of excellence possessed either in a less degree, or perhaps not 

 at all, by the other. Judging alone from the recorded failures 

 of the two metals in actual service, wrought iron appears 

 preferable to steel. However, an entirely just interpretation 

 of this record must recognize the fact that a majority of the 

 total failures of steel stand-pipes may be traced to the use of 

 ill-adapted or exceptionally inferior grades of that metal. 

 With this qualification, the contrast in the records of the t\vo 

 materials is much reduced, if indeed it is not quite elimin- 

 ated. Careful consideration of the foregoing records and 

 facts related thereto leads to the following conclusions : 



"(i) That steel plate of cheap grades is certainly a 

 dangerous material to use in the construction of stand-pipes. 



