42 ANNUAL OF SCIENTIFIC DISCOVERY. 



inferior iron for this purpose, and its employment inevitably led to a 

 loss of character in the structure, and danger to the public. 



CRYSTALLINE STRUCTURE OF IRON INDUCED BY VIBRATION. 



The spontaneous change forged and rolled iron undergoes when 

 submitted to continuous vibration, is productive of so much critical 

 danger, especially in the case of railway machinery, that an investi- 

 gation into the best means of remedying the resulting evils has been 

 viewed as an engineering question of vital importance. Among 

 others, Mr. Schimmelbuch, of Liege, has undertaken the subject, and 

 the following is an epitome of his investigations : A bar of pure unal- 

 loyed iron was struck by a hammer three times in a minute for six 

 consecutive weeks ; at the expiration of this time it broke into three 

 pieces. Before the experiment the bar was a good specimen of 

 fibrous iron ; after, on the contrary, its fracture exhibited a brilliant 

 crystallized structure, resembling that of antimony. 



A bar of iron alloyed with nickel, submitted to the same treatment, 

 underwent no change. 



A very simple means exists of recognizing this changed condition 

 of iron, so dangerous in its consequences. Pure iron, when mag- 

 netized by contact, loses its magnetic properties immediately the 

 needle is detached. On the other hand, iron combined with minute 

 quantities of some foreign body, such as carbon, oxygen, sulphur or 

 phosphorus, remains magnetized. The efficacy of this simple test has 

 been established by repeated experiments. London Photographic 

 News. 



Under the patronage of the Austrian government M. Bourville 

 has also recently instituted a course of experiments with a view of 

 throwing some additional light on the subject of the induction of a 

 crystalline structure in wrought iron through vibrations. 



M. Bourville's apparatus consisted of a bent axle, which was 

 firmly fixed up to the elbow in timber, and which was subjected to 

 torsion by means of a cog-wheel connected with the end of the hori- 

 zontal part. At each turn the angle of torsion was twenty-four de- 

 grees. A shock was produced each time that the bar left one tenth 

 to be raised by the next. Seven axles were submitted to the trial. 

 In the first the movement lasted one hour, 10,800 revolutions, and 

 32,400 shocks being produced ; the axle, two and six-tenths inches in 

 diameter, was taken from the machine and broken by a hydraulic 

 press, and no change in the texture of the iron was visible. In the 

 second, a new axle, having been tried four hours, sustained 129,000 

 torsions, and was afterward broken by means of a hydraulic press ; 

 no alteration of the iron could be discovered by the naked eye on 

 the surface of rupture, but, tried with a microscope, the fibres ap- 

 peared without adhesion, like a bundle of needles. 



A third axle was subjected, during twelve hours, to 338,000 tor- 

 sions, and broken in two ; a change in its texture and an increased 

 size in the grain of the iron were observed by the naked eye. In the 

 fourth, after one hundred and twenty hours, and 2,588,000 torsions, 

 the axle was broken in many places ; a considerable change in its 

 texture was apparent, which was more striking toward the centre, 



