342 JOURNAL OF FORESTRY 



a logarithm, n does not, which is consistent with the type of paper 

 we are discussing. 



The significance of this is that if a growth curve can be plotted 

 on this paper the slope of the curve at any given point will indicate 

 the growth per cent at that point instead of the current annual 

 growth, as is the case with ordinary cross-section paper. If it is 

 desirable to bring this figure out numerically a series of straight 

 lines radiating from the origin can be drawn, representing 1, 2, 3, 

 etc., per cent. The slope of the curve at any point can be compared 

 readily with these. These lines can be plotted with little trouble by 

 obtaining a single point on the 1 per cent line by computation or 

 from interest tables. If the 1 per cent line is then drawn with a 

 straight edge, the 2 per cent line will have just double its slope, and 

 so on for the other lines. All of them can thus be located by spacing 

 ofT with dividers equal intercepts with any verticle line. 



While this property is interesting, and is of some value in certain 

 cases, the main value of arithlog paper is the same as that of log- 

 arithmic paper, that a more compact graph is secured, accompanied 

 witfi consistent accuracy in plotting and reading high and low values. 



Certain minor difficulties are involved in the case of both log- 

 arithmic and arithlog papers. In the first place, the converging scale 

 may prove somewhat perplexing to the inexperienced. This difficulty 

 is just that met with by the novice in handling a slide rule, and should 

 be very transient. More serious is the fact that there is but a small 

 variety of such papers on the market. While ordinary cross-section 

 paper can be had in almost any conceivable size and spacing, I have 

 been able to find but four or five patterns of logarithmic and but one 

 of aritlilog paper. Those available are, however, sufficiently varied 

 to be entirely serviceable in solving many of the common problems 

 of forest mensuration. 



Note. — Instead of plotting cubic volumes of trees on the basis of diameter. 

 they can be plotted on the squares of the diameters. Thus the ordinates would 

 remain volumes, but the abscissse would be the squares of the corresponding 

 diameters. The advantages of this method are that ordinary cross-section paper 

 can be used, and that, because they are plotted and read on an arithmetical scale, 

 the plotting and reading of values is simpler. This is the method used by the 

 Forest Service. — Ed. 



