. Canadian forest industries 1886-1888. Lumbering; Forests and forestry; Forest products; Wood-pulp industry; Wood-using industries. structure, cannot take place without first crush- ing the medullary rays, hence the effect of the shrinking finds relief by splitting in another dir. ection, namely in radical lines from the centre, parallel with the medullary rays, thereby enab- ling the tree to maintain its full diametor, a shr<wn in Fie 1. If the entire tubular fibre composing the tree were to contract bodily, then the medullary rays would of necessity have to be crushed in the radial direc
. Canadian forest industries 1886-1888. Lumbering; Forests and forestry; Forest products; Wood-pulp industry; Wood-using industries. structure, cannot take place without first crush- ing the medullary rays, hence the effect of the shrinking finds relief by splitting in another dir. ection, namely in radical lines from the centre, parallel with the medullary rays, thereby enab- ling the tree to maintain its full diametor, a shr<wn in Fie 1. If the entire tubular fibre composing the tree were to contract bodily, then the medullary rays would of necessity have to be crushed in the radial direction to enable it to take place, and the timber would thuB be as much injured in proportion as would be the case in crushing the wood in the longitudinal direction. If such an oak or beech tree is cut into four quarters, hy passing the saw twice through the centre at right angles, before the contracting and splitting Pig. 3 1 of the workshop, they would be square, but, after being stored in a dry place, say for a year it would then be seen that a great charge had taken place both in the form, and in some of the dimensions ; the lines ca,cb, wou'd he the same length an before but it would bate con- tracted from a to b very considerably, and the two c a, and C b, would not be at right angles to each othsr by the portion here shown in black in Fig. 3. The medullary rays are thus brought closer by the collapsing of the vertical fibre. But supposing that six parallel saw cuts are passed through the tree so as to form it into seven planks, as shown in Fig. 4, let us see what would be the behavior of the several planks. Take the centre plank first. After due season, ing and contracting, it would then be found that the middle of the board will still retain the original thickness, from the resistance of the medullary rays, while it will be gradually re. duced in thickness toward the edijen for the want of support, and the entire breadth of the. plank would be the same as it was at fir
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectforestsandforestry
