43 
BULLETIN 835, U. S. DEPARTMENT OF AGRICULTURE. 
line is curved. By trying different constants, the logarithmic line 
changes in curvature, so that such constants may be found which 
make the logarithmic line straight. 
Logarithmic cross-section paper may be purchased which has both 
coordinates divided in logarithmic scale and also semilogarithmic 
cross-section paper having one ordinate so divided. When evalua- 
tions of equations having constant terms are to be made, these papers 
are very convenient, since the curves may be plotted without looking 
up the logarithms; but since the method described by Steinmetz 
0.4- 
Log days (Log x) 
0.6 o.e i.o 1.2 /.4 
Da Y #°(X) 25 3 ° 35 4 ° 
Fig. 8. — Method of developing formula for movement of moisture in flume 43. 
requires logarithms to be tabulated in order to calculate the con- 
stants, common cross-section paper will usually suffice. 
In figure 8 the data representing moisture movement in flume 
£3 are plotted. The values of log y and log as are also plotted and 
found to be a straight line, so that log y=log a-\-n log a? and the 
curve is a parabola. Table 36 gives the data, the logarithms of 
x and y and the calculated log y as obtained from the formula which 
was derived. 
