178 SECTIONAL ADDRESSES. 
1 2 3 4 5 6 7 8 
1. Area of ossification oe 88 60 62 43 31 25 26 
2. Ratio of ossification .. 88 52 58 41 74 24 29 
3. Height .. a .. 60 52 69 44 51 45 11 
4. Weight .. ae e162 58 69 65 39 40 83 
5. Chest girth af AS 41 44 65 59 36 69 
6. Lung capacity .. ae eit! 21 51 39 59 46 26 
7. Strength of Bei Sea) 24 45 40 36 46 14 
8. Nutrition 22°26 29 11 83 69 26 14 
Let us, then, look at the median tetrad-difference derived from this 
table and compare it with the probable error to be expected from sampling 
alone; the respective values are .089 and .011. That is to say, the 
actually observed value is no less than eight times greater than what theory 
demands. Here again we can examine the whole frequency distribution. 
Tetrad-Differences of A. Gates (115 subjects). 
The explanation of the figure is the same as in the preceding case of 
Simpson. 
& 
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' 
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' 
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1 
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a b ad 
1 ' 1 
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1 
beyond “055 -033 -Oll -0 +-0l1 -033 -055 beyond 
Between the curve showing the values to be expected from the errors 
of sampling and the rectangles showing those actually observed there is 
this time no agreement whatever. 
III. Law of Diminishing Returns. 
So much for the strengthening of the doctrine. I will now proceed to 
describe a rather curious matter that has arisen in the course of its 
elaboration. 
Since the very beginning it has been known that the two factors, 
g and s, the energy and the engines, may have widely different relative 
importance, according to the particular mental operation involved. With 
some operations the superiority of one person over another is prepon- 
derantly decided by their respective amounts of the energy. With other 
operations, on the contrary, the dominant factor is the engine. 
Subsequent research, moreover, has been gradually outlining the cases 
which incline in the one or the other direction. Thus the energy is in general 
