378 Forestry Quarterly. 



arts. The course then falls naturally into two sections, namely 

 Timber Physics and Wood Technology ; the former discussing the 

 structural, physical, mechanical and chemical properties of wood ; 

 the latter describing the uses, depending on these properties, which 

 are or could be made of them. 



Structure of Wood. Under this head there should be covered 

 the external features of wood, the structural elements of wood, 

 the value of structural cha'racteristics in identifying and classify- 

 ing woods and their products, and the classification and identifi- 

 cation of commercial woods. This subject is regarded by some 

 as properly a part of dendrology. It is more often taught in 

 schools in connection with the course in Forest Products. With- 

 out question the study of the structure of wood may be handled to 

 very great advantage together with the study of the other 

 characteristics of wood. It is believed also that the ordinary 

 student gains more from the course when it is given in the latter 

 part of the curriculum than when it is taken up at the beginning 

 in connection with dendrology. In addition, it is important to 

 correlate the structural characteristics of the wood with their 

 physical, mechanical and chemical qualities. 



Physical Properties of Wood. Under this head are considered 

 those properties manifest to the unaided senses, like color, odor, 

 taste, touch, and resonance; properties determined by measure- 

 ments like density, w^eight, moisture content, shrinkage, warping, 

 permeability and hygroscopicity. This section of the course con- 

 siders the subject of drying of wood, including a discussion of 

 methods of seasoning lumber, unless this problem has been taken 

 care of in utilization. 



Mechanical Properties of Wood. These are based on the be- 

 havior of wood when subjected to external stresses, as determined 

 by various methods of timber testing. They include strength 

 (compression, tension, shear, and torsion), stiffness, resilience, 

 toughness, and cleavability. A discussion of the mechanical 

 properties of wood should include the factors which affect these 

 properties like defects, rate of growth, moisture, temperature, and 

 preservatives. It is believed that enough instruction should be 

 given in timber testing to thoroughly fix in the mind of the student 

 the essential facts relative to the mechanical properties of wood. 

 Some institutions have a well-equipped timber testing laboratory. 



