INTRODUCTION. 



out a stick affects the general character and behavior of the same, will 

 appear from the following considerations : 



A square column or beam cut so as to contain the heart or pith of 

 the tree in its center — which, by the way, is the weakest part on 



Fig. 1. — A piece of sawn timber cut through along the pith, illustrating its structural aggregates. 



account of the many knots which it invariably and necessarily con- 

 tains — consists in the main of five structural aggregates (see fig. 1), 

 namely: (1) In the center a cone of wood fibers with the base in the 

 butt end and the apex in the top end, the base representing the rings 

 of as many years as it took the tree to attain the height of the column; 

 none of the fibers belonging to these rings appear in the top section 

 excepting those of the last ring which forms the apex of the cone; (2) 

 a hollow cylinder of material surrounding the cone, all fibers of which 

 are found in both sections and con- 

 tinuously through the whole length 

 of the column ; all the entire rings at 

 the bottom belong in this cylinder, 

 and undoubtedly form the strongest 

 part of the column ; (3) surrounding 

 this cylinder a partial cylindrical 

 envelope of wood fibers, all of which 

 are represented in the top section, 

 but only a part appear at the corners 

 of the bottom ; most of them, there- 

 fore, do not run through the whole 

 length, but are cut through at vary- 

 ing lengths, thereby presenting the 

 "bastard faces" on the sides of the 

 column; (4) a partial envelope whose 

 radial extent is limited by the corners of the basal section, imperfect at 

 both ends; (5) the corners at the top, three- sided pyramids with the 

 base in the top section, the fibers running out at varying lengths. 



Now, it will be readily admitted that each of these " structural aggre- 

 gates" has a different value in the combined strength of the whole. If 

 the stick be cut with the center or pith in one side (see fig. 2) all 

 these aggregates will be halved; if the stick be cut out differently, 

 for instance, with the heart entirely out or if it be made longer or 



Fig. 2 



9 >* 



Possibilities of cutting timber from a 

 log with reference to position of grain. 



