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(18) Iron, when fractured suddenly, presents invariably a crystalline 
appearance; when fractured slowly, its appearance is invariably fibrous. 
(19) The appearance may be changed from fibrous to crystalline by 
merely altering the shape of specimen so as to render it more liable to 
snap. 
(20) The appearance may be changed by varying the treatment so as to 
render the iron harder and more liable to snap. 
(21) The appearance may be changed by applying the strain so suddenly 
as to render the specimen more liable to snap, from having less time to 
stretch. 
(22) Iron is less liable to snap the more it is worked and rolled. 
(28) The “ skin” or outer part of the iron is somewhat harder than the 
inner part, as shown by appearance of fracture in rough and turned bars. 
(24) The mixed character of the scrap-iron used in large forgings is 
proved by the singularly varied appearance of the fractures of specimens cut 
out of crank-shafts. 
(25) The texture of various kinds of wrought-iron is beautifully developed 
by immersion in dilute hydrochloric acid, which, acting on the surrounding 
impurities, exposes the metallic portion alone for examination. 
(26) In the fibrous fractures the threads are drawn out, and are viewed 
externally, whilst in the crystalline fractures the threads are snapped across 
in cluster^, and are viewed internally or sectionally. In the latter cases the 
fracture of the specimen is always at right angles to the length; in the 
former it is more or less irregular. 
(27) Steel invariably presents, when fractured slowly, a silky fibrous 
appearance; when fractured suddenly, the appearance is invariably granu¬ 
lated, in which case also the fracture is always at right angles to the length; 
when the fracture is fibrous, the angle diverges always more or less from 
90°. 
(28) The granulated appearance presented by steel suddenly fractured is 
nearly free of lustre, and unlike the brilliant crystalline appearance of iron 
suddenly fractured ; the two combined in the same specimen are shewn in 
iron bolts partly converted into steel. 
(29) Steel which previously broke with a silky fibrous appearance is 
changed into granular by being hardened. 
(30) The little additional time required in testing those specimens whose 
rate of elongation was noted, had no injurious effect in lessening the amount 
of breaking strain, as imagined by some. 
(31) The rate of elongation varies not only extremely in different qualities, 
but also to a considerable extent in specimens of the same brand. 
