vi PREFACE 



The object sought in Part III is to systematize the principles and 

 problems confronting the student in the stud}' of tree growth, and to so 

 correlate these problems that he is not diverted from the ultimate object 

 of such^ studies, which is the determination of yields per acre, by details 

 of methods having to do with the measurement of growth of individual 

 trees. Research and field studies of growth per acre are rendered dif- 

 ficult not only by the lack of an accepted unit of measure, but bj' the 

 great variations in the character of the stands comprising our virgin 

 and second growth forests, yet it is just these stands, and not planta- 

 tions, whose growth will determine our yields of timber for the next 

 four or five decades. 



Attention is called to the substitution of the International j-inch 

 kerf log rule in the present volume, for the |-inch kerf rule in 

 Graves' Mensuration. It is hoped that this rule will be accepted as a 

 scientific standard for board feet since it is adapted to conditions of 

 second growth and is conservative in values. 



Instead of attempting to include tables of volume or yield, a table 

 of references is printed to such tables as are of standard quality and 

 which are in possession of the U. S. Forest Service, Washington, D. C. 



The author wishes to acknowledge the many helpful criticisms 

 received from foresters in the preparation of this book. 



