Porter — The Physical Basis of Precocity and Dullness. 173 
The coincidence of high weights and high school grades so 
clearly demonstrated by previous tables is seen with equal 
clearness here. Small dull children are under, small preco- 
cious children above the mean weight of small children of 
their age, and the same is true of large children. 
If weight is indeed a good index of physical development, 
it is @ prior? probable that height, girth of chest and other 
dimensions follow the law induced above. An analysis of 
the measurements at any age will show that this assumption 
is well grounded. Age 10, boys, and age 12, girls, may be 
selected for this purpose, as the number of observations at 
these ages is large and the pupils are found in several grades. 
The analysis of the height standing of boys aged 10 and girls 
aged 12 is seen in Tables No. 8 and No. 9 respectively. 
TABLE NO. 8. 
The Mean and the Average Height Standing of Boys, Aged 10. 
No. of Obser- 
School sean Mean. Average. __ vations. 
ec nce Soe OS See ne Ie Gres oe 126.50 cm. 126 18cm. 109 
‘ Set eRe eae kee cee oe 129.39 128.78 440 
TE a ea aes 130.29 129.96 436 
lh ee ay ee 131.22 131.99 185 
Vos Serta eee ae era or er a ee ee 11 
Viiv csp overs e eenes cree ee ee eee 3 
TABLE NO. 9. 
The Mean and the Average Height Standing of Girls, Aged 12. 
No. of obser- 
School Grade. Mean. oe vations. 
| ae rr ee he oe eee ee 14 
Th cetey eet ea et 136. 06 cm. 135.93 cm 73 
PRs seca ve Cece tee 139.04 138.97 7 
FA eee re Sn ec <2 40.08 139.77 395 
Nivsi se xeteane ese eee me aewenee hee 3 * 140.57 227 
a oe ee wk es cer ba esa Soke OU 141.80 110 
WE a a eek ek caver oS wees ws 14 
It appears that precocious children are taller as well as 
heavier than dull children. 
The measurement of the girth of chest in girls is more 
difficult than in boys, and in both sexes is more subject to 
error than the measurement of weight or height. For this 
reason it is advisable, at least in the case of girls, to divide 
