u Antonio Alzate 325 
the laboring classes, bright in language) would be wholly unk- 
nown in advance. 
In reporting the pupils as brigth, dull, or average, the 
teachers were told to mark them average whenever in doubt. 
In this way there was less liability to error in regard to the 
brigth and dull, which are the classes we desired most to com- 
pare. The teachers reported upon those pupils whom they knew 
best. The pupils were marked after the measurements were 
made. 
RESULTS OF INVESTIGATION. 
Itis a general principle in new lines of inquiry to regard 
the results as more or less tentative according to the number of 
experiments made. In this work the results depend upon aver- 
ages, which are valuable according to the whole numbers from 
which the averages are made. The conclusions, therefore, will 
be more trustworthy the larger the nambers measured. In many 
instances those numbers are not as large as one would desire; 
but this will induce some investigator to make experiments 
upon larger numbers. 
CUNCLUSIONS AS TO ALL THE SCHOOL CHILDREN (21,930) 
1. As circumference of head increases mental ability in- 
creases.' 
2. Children, of the nonlaboring classes? have a larger ciroun- 
ference of head than children of the laboring classes. 
3. The head circumference of boys is larger than that of girls, 
1 It being understood that the race is the same. 
2 “Non-laboring classes” refer to children, whose parents are engaged 
in mercantile professional occupations. 
