KOTE ON A EEMARKABLE EXAMPLE OF FRACTURE 

 IN KEROSENE SHALE. 



By Felix Rattb, M.E. 



(Plate IV.) 



The figure that I give, of the specimen exhibited at this meet- 

 ing will, I hope, afford material for the study of fracture. It 

 involves questions of mineralogy, mechanics and geology. 



In minerals the form of the fracture depends generally upon 

 ditferences of elasticity along different axes, and it is evident 

 that, besides this, the greater the homogeneity of the mineral, 

 the nearer the form of the fracture will be to that determined 

 by theory. 



Some specimens of the so-called "Kerosene Shale" exhibit a 

 perfect conchoidal fracture due to homogeneity. The fracture 

 here represented is, no doubt, very complicated ; but I suggest 

 that it might be due to vibration, the lines of fracture occuring 

 along the nodal lines. I also suggest that, as some of the 

 specimens of shale show a very distinct plane of easy fracture 

 (stratification marked by fossil ferns), this might account for the 

 existence of what is very nearly a plane of symmetry in the 

 specimen. 



In order to show how the fracture might have been determined 

 by the nodal lines I have represented a cross-section exhibiting 

 undulating curves and their intersections. 



Little is known of the analytical problem raised as regards non- 

 crystallized solids unless homogenous, and direct experiments 

 would certainly throw some light on the subject, as well as on the 

 molecular constitution of Torbanite or " Kerosene Shale." 



