ALINEMENT CHARTS IN FOREST MENSURATION 



775 



types which, with their variations, singly or in combination, will be seen 

 to be adequate for the solution of a very large number of problems. In 

 fact, almost any equation can be handled by these two fundamental 

 forms, but certain more complicated expressions give far better results 

 if less simple types of graphs involving curved lines are used. 



Fig. 2. — Elementary chart for addition, using different scales for the initial axes. 



ADDITION OF VARIABLES 



The fundamental chart form for such an addition as is expressed by 

 an equation of the form s = x-\-y consists of three parallel straight 

 lines, the two outer lines being the initial axes, and the intermediate 

 line, placed commonly half way between them, the final axis. Figure i 

 illustrates such a graph. AB and EF are the initial axes of x and y, 



