104 NATURAL INHERITANCE. [C-11 AP,
Thus 56 is written in the position of 60.48 inches, which is equal to 56 x 1'08. Similarly, 60 is written in the position of 64.80, which is equal to 60 x 1.08.
It is obvious that raising M will cause F to fall, and vice versa, without affecting the wheel AB, and therefore without affecting SD ; that is to say, the Parental Differences may be varied indefinitely without affecting the Stature of the children, so long as the Mid-Parental Stature is unchanged. But if the Mid-Parental Stature is changed to any specified amount, then that of SD will be changed to 2 of that amount.
The weights M and F have to be set opposite to the heights of the mother and father on their respective scales ; then the weight SD will show the most probable heights of a Son and of a Daughter on the corresponding scales. In every one of these cases, it is the fiducial mark in the middle of each weight by which the reading is to be made. But, in addition to this, the length of the weight SD is so arranged that it is an equal chance (an even bet) that the height of each Son or each Daughter will lie within the range defined by the upper and lower edge of the weight, on their respective scales. The length of SD is 3 inches, which is twice the Q of the Co-Fraternity ; that is, 2 x 1.50 inch.
d. Fraternal : In seeking for the value of Fraternal Regression, it is better to confine ourselves to the Special data given in Table 13, as they are much more trustworthy than the R.F.F. data in Table 12. By treating them in the way shown in Fig. 13, which is constructed on the same principle as Fig. 10, page 96,
