760
POPULAR SCIENCE MONTHLY.
eleven (position on chart at 0, a year and a half above the average of their age), shows the vertical recorded nearly upright fifty-one times, greatest variation twenty degrees, while the oblique
lines of the trapezium show the maximum possible variation forty-five degrees, with few lines near the right slant.
The so-called child drawing, so much written about of late, that Herbert Spencer and many others deem of educational importance, may be described as line making without conscious effort—the graphic record of a muscular movement associated with a concept. It becomes more plausible as years advance, but never gets beyond caricature, and has no direct educational value.
Drawing, to have educational value, must be the graphic record of a perceived fact.
- ↑ divided by 2. To get per cent, divide by 2 again and subtract from 100, because 2100 inch = 1 per cent. Thus, total error, 2·1 inches; greatest angle error, 7·2°.
When time is limited and an approximation is desired, the greatest angle error treated as above will give a result within two per cent of an average for a class. The angle error may be ignored where the personal position is not desired, as it will change the average center but little, the personal position very much, particularly of the concept recorders.2·1 ÷ 7 = ·3; 7·2 ÷ 24 = 3; ·3 ·3 100 ·6 ÷ 2 = ·3 ÷ 2 = ·15; ·15 85 per cent.