INTRODUCTION 



As the available supply of the standard kinds of timber has 

 decreased, woods have appeared on the market which formerly 

 were considered worthless. In some instances the new woods are 

 sold under their own names, but usually they are employed as 

 substitutes for more expensive kinds, or sold in indiscriminate 

 mixture. It thus becomes a matter of great importance that 

 foresters, timber-inspectors, and wood-users be able to distinguish 

 the woods with which they deal. The number of such woods is so 

 large, and their resemblance often so close, that one can no longer 

 depend upon distinguishing them through mere familiarity with 

 their general appearance. To identify woods it is necessary to 

 have a knowledge of the fundamental differences in their structure 

 upon which the points of distinction are based. 



The literature bearing directly upon this subject is very 

 limited, and such information as exists is for the most part dis.- 

 tributed throughout a considerable number of publications and not 

 readily available. Teachers and students of wood technology are 

 seriously handicapped by the lack of suitable text-books or 

 manuals. It is in an attempt to supply in small part this defi- 

 ciency that ;the writer has prepared for publication a portion of the 

 material given in one of his courses in Forest Products at the 

 Yale Forest School. While it is designed primarily as a manual 

 for forestry students, it is hoped that it will also aid others in the 

 study and identification of wood. 



Part I deals briefly with the more important structural and 

 physical properties of wood. The structural properties are based 

 upon the character and arrangement of the wood elements. 

 Under this head are considered: (a) the external form of the tree 

 in its various parts; (b) the anatomy of the wood; (c) abnormal 

 developments or formations; (d) relation of these properties to 

 the usefulness of wood; and (e) their importance in classification. 

 The physical properties are based upon the molecular composition 

 of the wood elements. Under this head attention is given to 

 (a) the properties manifest to unaided senses, viz., color, gloss, 



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