728 KANSAS CITY REVIEW OF SCIENCE. 



engineers. Professor Thurston's thorough discussion will perhaps, for a time 

 at least, silence the prating of newspaper engineers about "vibration," "crystalli- 

 zation," "decay," and what not. 



We cannot forbear to quote a few sentences : 



"So far as I am aware, and so far as I can ascertain, there is no evidence 

 extant, and nothing to give the slightest foundation to the belief, that good 

 wrought-iron, loaded within the elastic limit, will ever yield either to stationary 

 or to intermittent unreversed loads, or that crystallization can ever take place 

 under such conditions. 



"Thus, that distinguished engineer, the late Mr John A. RoebUng, report- 

 ing upon the condition of the great Niagara suspension bridge several years after 

 its construction, states : 'After a thorough examination, I am unable to report 

 any change.' Experiment exhibited the same deflection as when the bridge was 

 first built, and no evidence of loss of strength or stiffness was detected by his 

 repeated measurements of the bridge under load. The same engineer, remov- 

 ing the old aqueduct over the Alleghany river, at Pittsburg, after forty years 

 of continuous service, found the iron suspension-rods to be quite equal in 

 quality to new iron. It was used again in a new structure. Tie-bars that had 

 been in service underground, imbedded in clay for twenty-five years, were 

 found in equally good condition as to quality of the metal. The old St. Clair Street 

 bridge, near the same locality, after forty years of service, was taken down to 

 make place for the later suspension bridge at Pittsburg, and its iron was 

 unchanged in quality. Iron originally crystalline remained so ; the iron found 

 fibrous at its removal was fibrous when first used ; no change in either direction 

 had taken place. 



"Testing iron wires from the oldFairmouat suspension bridge, taken down 

 a few years since to make room for the new and stronger truss-bridge at Phila- 

 delphia, over the Schuylkill, and comparing it with good merchant qualities of 

 wire of the same gauge, I found the two lots of wire substantially the same 

 in quality. Thirty years of work had not apparently affected the wire of the 

 bridge in the least." 



It is a serious question, and one which time only can completely answer^ 

 whether steel structures will prove as uniformly and permanently reliable as 

 wrought-iron has proved to be, or in other words, whether the fibrous texture of 

 wrought-iron can be equaled in this respect by the granular texture of steel or 

 of ingot iron. In this connection, it is interesting to note that the fibrous texture 

 referred to is imparted to wrought-iron by the presence in it of a small proportion 

 of slag from the puddling-furnace ; and that this can be secured in the Bessemer 

 converter also, if desired. The so-called Kleinbessemerei, carried on at Avesta,. 

 in Sweden, for several years past, produces exclusively soft, fibrous iron by the 

 simple device of pouring slag and iron together into the ingot-mould. This 

 requires however, a very small charge (usually not more than half a ton), and a 

 direct pouring from the converter, without the intervention of a ladle, which 

 would chili the slag. 



