138 



The Action of Catting Tools. 



[Dec. 8, 



each atom from the opposite one to which it was attached." C£ 3 is of 

 course dependent on the bending and material. 



As to the first of these terms, I have shown that it is =0 when the 

 tool is sharp ; and the second must be small, in the first place, because 

 but little true bending occurs, and, secondly, because the resistance 

 which a shaving can oppose to bending is, on account of its laminated 

 structure, very feeble. 



Note 2. — Though the general line of shearing is in the direction e, c, 

 it can hardly be doubted that separation first occurs across the lines of 

 greatest tension. 



Fig. U 



Let f, g, h, h, be a small cube of substance contiguous to ec, and 

 unstrained ; let f, g\ h', be the same substance when strained and 

 just about to shear. The lines of greatest tension are parallel to p, g', 

 and rupture will take place in a direction at right angles to this. 



Ruptures of this kind will happen all along the line ec, and the 

 saw-tooth-edge left will be rubbed down when the lamina begins to 

 slide. 



Fig. 15. 



Paper ruptured by distortion. 



