Fig. 2

Reduced area plotted against plate number (smallest to largest) for plates numbered from 46 to 115. The reduction emphasizes the statistically significant difference in slope between the smaller data set (plates from 46 to 80) in contrast to the larger plates (plates from 81 to 115). This suggests that the nick point seen in Fig. 1 separates plates that may have been caused by different phenomena. The data for this figure were obtained from some of the data shown in Fig. 1 by plotting Y´ in place of Y, where ln(Y´) = ln (Y) − 0.0481 * X which had a slope halfway between the slopes shown in Fig. 1. Z values are the transformed correlation coefficients (Fisher 1958), and the Sigma Z values are the standard errors (which depend only on the number of data pairs) of the Z values