( 286 ) 



On some Peculiar Changes in the Internal Structure of Iron^ 

 independent oJ\ and subsequent to^ the several Processes of 

 its Manufacture. By Charles Hood, Esq., F.R.A.S., &c.* 



Thb important purposes to which iron is applied have always rendered 

 it a subject of peculiar interest; and at no period has its importance been 

 so general and extensive as at the present time, when its application is 

 almost daily extending, and there is scarcely any thing connected with 

 the arts, to which, either directly or indirectly, it does not in some de- 

 gree contribute. My object in the present paper is to point out some 

 peculiarities in the habitudes of iron, which appear almost wholly to have 

 escaped the attention of scientific men ; and which, although in some 

 degree known to practical mechanics, have been generally considered by 

 them as isolated facts, and not regarded as the results of a general and 

 important law. The circumstances, however^ well deserve the serious 

 attention of scientific men, on account of the very important consequences 

 to which they lead. The two great distinctions which exist in mal- 

 leable wrought iron, are known by the names of '' red-short" and " cold- 

 short" qualities. The former of these comprises the tough fibrous iron, 

 which generally possesses considerable strength when cold ; the latter 

 shews a bright crystallized fracture, and is very brittle when cold, but 

 works ductile while hot. These distinctions are perfectly well known to 

 all those who are conversant with the qualities of iron ; but it is not 

 generally known that there are several ways by which the tough red-shot 

 iron becomes rapidly converted into the crystallized, and hy this change 

 its strength is diminished to a very great extent. 



The importance which attaches to this subject at the present time, 

 will not, I think, be denied. The recent accident on the Paris and Ver- 

 sailles Railway, by which such a lamentable sacrifice of human life has 

 occurred, arose from the breaking of the axle of a locomotive engine, 

 and which axle presented at the fractured parts the appearance of the 

 large crystals, which always indicate cold-short and brittle iron. I believe 

 there is no doubt, however, that this axle, although presenting such decided 

 evidence of being at the time of this accident of the brittle cold-short 

 quality, was at no distant period tough and fibrous in the highest decree ; 

 and as die P'rcnch government have deemed the matter of suflicient im- 

 portance to be inquired into by a special commission, I trust that some 

 remarks on the subject will be interesting to the members of the Institu- 

 tion of Civil Engineers. I propose, therefore, to shew how these extra- 



* Read before the Institution of Civil Engineers, June 21, 1842, and communi- 

 cated by the Author to the twenty-first volume of the Philosophical Magazine, 

 from which periodical we have extracted it. 



