1906.] on the Internal Architecture of Metals. 257 



state of knowledge, could not be detected, except in rare cases, by the 

 microscope. It was suggested that this molecular structure was 

 brought about by improper heat treatment developing in the ferrite 

 from a series of centres well developed mineral cleavage. On the cir- 

 cumference of these centres existed areas in which the molecular 

 cleavage was less perfectly developed, and beyond these were the areas 

 of good steel in which the cleavage lines were extremely imperfect. 

 It was then easy to conceive that the plane of dynamic fracture in a 

 perfectly developed cleavage area might give the remarkably low- 

 record of having endured only 230 alternations as in the table pre- 

 viously exhibited on the screen, whilst a test-piece in which the plane 

 of fracture went through an area of good steel free from what might 

 be called cleavage disease might readily endure 1290 alternations 

 before breaking, and a third test piece from the middle zone of some- 

 what developed cleavage might endure say 700 alternations. This 

 theory at any rate was in accordance with the mechanical facts which 

 had been presented. Another step towards the experimental verifica- 

 tion of this hypothesis would be to prove that iron was a veritable 

 mineral, as capable of exhibiting geometrical cleavage as was, say, 

 fluor-spar or Carrara marble. Fortunately the lecturer found himself 

 in a position by what might be called a million-to-one chance, to 

 clearly prove that iron could possess absolutely perfect mineral cleavage 

 parallel to the faces of the cube. This discovery came in no heroic 

 form from the swift-moving machinery of a destroyer, or in connec- 

 tion with metal forming the stupendous engines of a battle-ship, but 

 in connection with a wTought-iron bolt, literally forming part of a 

 common or garden gate-post. This fractured under the taps of a 

 hand-hammer during repairs, and one of the crystals cleaved at 

 exactly right-angles to the axis of the bolt, and consequently when 

 the fractured end was cut off in the lathe for examination, it was 

 found at right-angles to the axis of the microscope, exhibiting the 

 wonderfully perfect cubic cleavage delineated in Fig. 3. 



Metallurgists had now arrived at a deadlock. The microscope 

 after rendering great services, had in its turn broken down, mainly 

 owing to the fact that optical examinations associated with transmitted 

 light, could not be applied to opaque objects, and in more senses than 

 one, the scientific metallurgist could not yet see through steel. 

 Nevertheless he must endeavour to tear down this mysterious veil, or 

 in some way get behind it, and in the lecturer's opinion the resources 

 of science in connection with steel metallurgy were not yet exhausted. 



[J. 0. A.] 



Vol. XVIII. (No. 100) 



