VI PREFACE 



structed in the classroom. The book was written to serve as 

 supplementary reading in this way. 



A forest type as here used is an area which has essentially the 

 same climatic, topographic, and soil conditions, and hence tends 

 in the long run to have the same composition. A subtype is a 

 subdivision of a forest type in which the composition is uniform. 



A word of explanation seems necessary in regard to prices now 

 that the War has so radically disturbed all our preconceptions 

 of market values. Obviously it is impossible to keep such a work 

 as this absolutely up to date. Care has, however, been taken to 

 give dates for all prices cited as that proper allowance may be 

 made. In general it may be said that the prices of 1920 are 

 roughly double those of 191 5. Furthermore, wherever possible, 

 costs are expressed in terms of man and horse hours as well as 

 dollars. 



Acknowledgment is, of course, due the Forest Service for its 

 courtesy in allowing the free use of its large store of data. 



