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JOURNAL OF FORESTRY 



moil graphic form is most evident. An equation of three variables can 

 be expressed in rectangular co-ordinates only by a series of curves (like 

 the harmonized curves of a volume table), while in the alinement form 

 these curves are replaced by three lines all of which are usually straight. 

 In the following pages are presented six charts applying to certain of 



Fig. I. — EleniL-ntary chart for addition. 



the most commonly used formulae of forest mensuration. In order to 

 make clear how they have been prepared, it is first advisable to explain 

 how such fundamental operations as addition, subtraction, multiplica- 

 tion, etc., may be handled. It should be understood that this explanation 

 makes no pretense at completely developing the theory of alinement 

 charts. As a matter of fact, it is restricted to two simple straight-line 



