40 NATURAL INHERITANCE. [CHAP.
of Rank (on a scale reckoned from 0° to 100°) of any person in the group to which he belongs. The measured strength of the person is to be looked for in the side scale of the Scheme ; a horizontal line is thence drawn until it meets the curve ; from the point of meeting a perpendicular is dropped upon the scale of Grades ,it the base ; then the Grade on which it falls is
FIG .6. 4'.
the one required. For example : let us suppose the Strength of Pull of a man to have been 74 lbs., and that we wish to determine his Rank in Strength among the large group of men who were measured at the Health Exhibition in 1884. We find by Fig. 4 that his centesimal Grade is 50*; in other words, that 50 per cent. of the group will be weaker than he is, and 50 per cent. will be stronger. His