36 ANNUAL OF SCIENTIFIC DISCOVERY. 



On the other hand, I am witnessing the fact daily, that vibration 

 and tension combined will greatly affect the strength of iron without 

 changing its fibrous texture. The cohesion and elasticity of wire and 

 wire rope will be rapidly destroyed by great tension and vibration 

 combined. AVhether J shall be able to account for it or not, there 

 stands the fact. But what is true of iron wire applies with equal 

 force, and, when all circumstances and conditions are duly propor- 

 tioned, with even greater force, to larger masses. The extensive 

 opportunities which my pursuits offer to make experiments and 

 observations on wire and wire rope, authorize a positive expression 

 on this subject. A great deal of fancy speculation has been indulged 

 in of late years on this question of granulation and crystallization, 

 but generally by men whose opinion can have no weight. 



Now, while the fact remains that iron and steel will lose their 

 strength by vibration and tension, it is proper to state, also, in this 

 connection, that this loss of strength bears a due proportion to the 

 extent and duration of the vibration and tension. Wire ropes may 

 lose their strength by three months' service, without exhibiting much 

 wear ; and they may also last ten years, running all the time, and be 

 greatly worn, before their strength is so far reduced as to be unfit to do 

 duty. I will state here, that there are now ropes of my manufacture 

 on the inclines of the Morris Canal, which have run nine years. 

 This great durability is owing to comparative absence of vibration, 

 in consequence of slow speed and good machinery, although a high 

 tension is maintained. 



The greater the elasticity and cohesion of the iron or steel, the bet- 

 ter it will support vibration and tension, always provided that the 

 extent of this vibration and the amount of tension are kept within 

 safe limits. Witness, as examples, the durability of watch springs, 

 piano wire, sofa and wagon springs, etc. etc. 



Wrought iron that has become brittle, as, for instance, chain, car- 

 axles, wire or wire rope, on being annealed, will have its softness 

 and apparently also its strength restored. As far as softness is 

 concerned, this is correct ; but in regard to strength, when applied 

 to wire or wire rope or to fine chains, it is a mistake. Soft annealed 

 wire possesses only half the strength which hard wire has, and is 

 without any elasticity. But wire rope without elasticity is 

 worthless ; very little work will make it brittle again and worse than 

 before. It is different with heavy chains and with car-axles. Made 

 of indifferent material, crystalline or brittle when new, they will be 

 greatly improved by an annealing process at the very beginning ; 

 and if this process is repeated from time to time, their lifetime may 

 be prolonged. I maintain that a good car-axle, made of good mate- 

 rial, and finished at the proper heat, by hammering or rolling, is 

 stiffer and stronger than the same axle, when again subjected to an- 

 nealing without hammering or rolling. Annealing restores softness, but 

 at the same time reduces cohesion and elasticity. To restore the iron 

 of a brittle car-axle fully, can only be done by a full heat, with ham- 

 mering or rolling, which of course will reduce its diameter. 



The opinion prevails, that a well drawn out fibre is the only sure 

 sign of tensile strength. This, however, is true only when applied 

 to ordinary qualities of bar or rail iron. The fact is different with 



