54 NATURAL INHERITANCE. [CHAP. 



These are not identical in value, because the outline of 

 the Scheme is a curved and not a straight line, but the 

 difference between them is small, and is approximately 

 the same in all Schemes. It will shortly be seen that 

 Q'=l'015xQ approximately; therefore a series of De- 

 viations measured in terms of the large unit Q' are 

 numerically smaller than if they had been measured in 

 terms of the small unit (for the same reason that the 

 numerals in 2, 3, &c., feet are smaller than those in the 

 corresponding values of 24, 36, &c., inches), and they 

 must be multiplied by 1.015 when it is desired to 

 change them into a series having the smaller value of Q 

 for their unit. 



All the 18 Schemes of Deviation that can be derived 

 from Table 2 have been treated on these principles, and 

 the results are given in Table 3. Their general accord- 

 ance with one another, and still more with the mean of 

 all of them, is obvious. 



Normal Curve of Distribution. The values in the 

 bottom line of Table 3, which is headed " Normal Values 

 when Q = 1," and which correspond with minute pre- 

 cision to those in the line immediately above them, are 

 not derived from observations at all, but from the well- 

 known Tables of the " Probability Integral " in a way 

 that mathematicians will easily understand by comparing 

 the Tables 4 to 8 inclusive. I need hardly remind the 

 reader that the Law of Error upon which these Normal 

 Values are based, was excogitated for the use of astro- 

 nomers and others who are concerned with extreme 



