540 



IRON AND STEEL. 



The samples which hardly elongated at all, 

 were of puddled-steel ship plates. One sample, 

 which bore 63,098 Ibs. per square inch of the 

 original area, stretched before breaking but 

 the ^ 5 th part of an inch in a length of 7.6 

 inches, or less than Aths of 1 per cent, of the 

 length. Adopting Mr. Mallet's co-efficient, the 

 structural value of such a material would be 

 almost nothing. In fact, Mr. Kirkaldy found 

 the pnddled-steel plates throughout to have 

 much less extensibility than cast-steel plates, 

 while the former also were of very irregular 

 breaking strength," 



Additional Facts respecting the Relation of 

 Vibratory Action, and Texture, to the Strength 

 of Iron. Prof. Wm. Fairbairn read before the 

 Royal Society, Feb. 4th, a paper detailing cer- 

 tain experiments made by him in regard to the 

 effects of impact, vibratory action, and long-con- 

 tinued change of load, upon wrought-iron gir- 

 ders, and with a view to determine the strength 

 and form of iron tubular bridges, and the ex- 

 tent of strain to which girders may safely bo 

 subjected. The arrangement he employed was 

 designed to imitate as nearly as possible the 

 strain to which bridges are subjected by the 

 passage of heavy trains, and also beams by 

 lowering the load quickly upon them, and by 

 producing a considerable amount of vibration. 

 His test girder was a wrought-iron plate beam, 

 20 ft. long. Upon it, by means o a mill driven 

 by water power, a weight was allowed to fall, 

 day and night, at intervals such as to produce 

 about 80 concussions a minute. From the re- 

 sults of these experiments, the conclusions are 

 drawn, that wrought-iron girders are not safe 

 when subjected to violent disturbances equiva- 

 lent to one third the weight that would break 

 them ; bnt that, when these are equivalent to 

 one fourth the breaking weight or blow, the 

 tenacity remains unimpaired. 



An abstract of this paper having been read 

 before the Polytechnic Association of New 

 York, March 17th, 1864, and a member having 

 stated that (as hitherto quite generally held) 

 vibratory motions tend to disintegrate wrought 

 iron by inducing in it a crystalline texture, 

 Mr. Fisher alluded to the opinion of the late 

 Mr. I. K. Brunei, to the effect that the peculiar 

 molecular arrangement of the iron in such cases 

 is not a result of the previous tremulous motions, 

 but is produced by the blow causing the frac- 

 ture a view which, at first, perhaps, appearing 

 to be the same with that of Mr. Kirkaldy, is in 

 reality quite different ; since the latter does not 

 allow that a granular or crystalline texture can 

 be produced in fibrous iron, but only that the 

 iron can have its fibres so broken as to simulate 

 such a texture. 



Mr. T. D. Stetson thought Fairbairn's ex- 

 periments and results chiefly valuable as an at- 

 tempt to show at what precise degree (concus- 

 sive) strainsbegintobedestructive. He was will- 

 ing to believe that the rapidity of the act might 

 greatly affect the appearance of the fractured 

 surfaces ; but any doctrine in this direction 



would be productive of evil if carried to the 

 extreme of supposing that there were not great 

 actual differences in the structure of metals. 

 He instanced as common the cases of axles 

 which, after breaking, showed that some of 

 the bars of which they had been formed were 

 far more fibrous than others piled in the same 

 axle. The great mass of cast iron which some 

 years ago, at the Novelty Works, in this city, be- 

 came cooled before it could be poured, was 

 when cold broken open in the slowest manner 

 by very tapering wedges ; but its interior was 

 found to be in large crystals, while its exterior 

 showed a fine texture. These results he infer- 

 red to be due to the facts that the outside of the 

 mass was cooled rapidly, and the inside very 

 slowly. The manner of breaking could not, in 

 this case, have affected the molecular arrange- 

 ment. 



Applications of Steel. At a late meeting of 

 the South "Wales Institution of Civil Engineers, 

 Mr. Parry stated that steel rails laid down on 

 the Midland Railway nearly 6 years ago, and 

 over which trains have since passed 700 times 

 daily, are to this hour uninjured. These rails 

 were made by Mr. Mushet's process. 



Rails of steel made by the Bessemer process 

 have been laid down in 1862, it would appear 

 on the London and Northwestern line. These 

 were laid parallel with others of the very best 

 iron ; and although, it is stated, the latter had 

 to be on several occasions renewed, the former 

 still showed very little appearance of wear. The 

 result, showing apparently a decisive advantage 

 of steel over iron rails, had led the directors to 

 arrange for the production, at Crewe, of 10,000 

 tons per annum of the new style of rail. 



Experiments have been made in Prussia to 

 ascertain the capabilities and advantages of 

 cast-steel steam boilers. Two cylindrical egg- 

 end boilers, one of steel, the other of wrought 

 iron, were brought into comparison, and, after 

 working 6 months, examined. They were 80 

 feet long and 4 feet in diameter. The steel 

 boiler plate was ^th inch in thickness ; and the 

 boiler tried by the hydraulic, test to a pressure 

 of 195 Ibs. to the square inch, showed neither 

 alteration in shape nor leakage. After working 

 six months, the cast-steel plates were found 

 quite unaffected, and, as compared with the 

 other boiler, had moreover a remarkably small 

 amount of incrustation. This boiler had aho 

 generated about jth more steam than the other. 

 Another examination was recently made of 

 boilers which had been in use 18 months. The 

 steel boiler was found in excellent condition; 

 and with about the same expenditure of fuel, it 

 had evaporated 11.66 cubic feet of water per 

 hour, against 9.37 cubic feet per hour by the 

 common boiler. 



Steel-wire ropes are now gradually displacing 

 those of iron wire, for hoisting minerals from 

 mines. The iron-wire ropes, in order to pos- 

 sess a given strength, must be much thicker, 

 and accordingly much heavier, than those of 

 steel. 



