NATUBE-STUDT LESSONS. 116 



12. (a) Observe other markings on the circular surface. 

 (^) Describe them. 



{c) Infer why these Hnes are called rays. 



13. {a) Using a strong knife try to split the block in 



various directions. 

 (l>) Along what lines do the blocks split most 

 easily ? 



14. («) Which kinds of wood split easily and which 



with difficulty? 

 {3) Find the reason in each case. 



15. (a) Try to split a block with knots. 



{d) Examine the split surface and explain why it 

 was difficult to split. 



16. (a) Cut slabs from the cylinders. 



(6) Explain why the blocks may be split in these 

 planes. 



(c) Examine and describe the split surfaces. 



(d) What relation do the lines on the split surfaces 



bear to the rings of growth ? 



17. Compare the graining in the different kinds of 

 wood. 



18. On what does the nature of the graining depend? 



19. Observe the effect of the following upon the 

 graining of the wood : — 



(a) The thickness of the annual rings. 

 (^) The regularity of these rings in shape. 



(c) The straightness of the stem. 



(d) The presence or absence of knots. 



(e) The coarseness or firmness of the wood-fibres. 



20. (a) Cut some of the cylinders into quarters. 

 (ff) Make slabs from these in various planes. 

 (e) Compare the graining in the several cases. 



