74 TOWERS AND TANKS FOR WATER-WORKS. 



mill employing the " open-hearth process of manufacture," a 

 preference being given to acid furnace-lining methods. 



The chemical qualifications for this metal shall be such as 

 to ensure the reduction of the metalloids to the following 

 limiting maximum percentages in the finished product: 



Phosphorus, .08; Sulphur, .05; Manganese, .60; Silicon, .04. 



Drillings for chemical analysis may be taken either from 

 test-piece or finished product, and if required, each of the 

 elements may be ordered determined. 



The simple tests of bending and drifting should be inserted 

 into the specifications for structural metal. It should be pro- 

 vided that from any melt or number of melts, test-specimens, 

 as strips, might be cut from the plate. Such strips should be 

 about ij inches in width, should be planed parallel, and, 

 when bent 180 degrees upon itself, either hot or . cold, 

 should fracture appear upon either the concave or convex sur- 

 faces of the curve, the melt may be subject to rejection. 

 Rejections should also be provided for if the material will not 

 stand, without injury, drifting a hole in test pieces to twice the 

 original diameter. Such holes are ordinarily about -j-f in. 



Inspection. That there may be no uncertainty or disap- 

 pointment as to results, it is necessary not only that the 

 constructive engineer shall know what to specify in ordering 

 materials, but he must be reasonably sure that he is getting 

 what he requires. No field-inspection or cursory examination 

 can be relied upon to reveal departures from the specifications 

 and fatal defects, and absolute certainty as to results can only 

 be secured through a close, systematic inspection during the 

 process of manufacture from the raw material to the finished 

 structure; it is obvious, therefore, that such careful attention 

 to details requires the constant presence of a skilled inspector 

 at the mill, the shop, and in the field. A knowledge of and 

 the ability to conduct the necessary series of chemical and 



