830 thirteen age classes were employed for free whites of each sex,
and six for the free coloured and the slaves of each sex. The number of
aliens, of the deaf and dumb and the blind were also gathered.

The law under which the census of 1840 was taken contained a novel
provision for the preparation in connexion with the census of
statistical tables giving "such information in relation to mines,
agriculture, commerce, manufactures and schools as will exhibit a full
view of the pursuits, industry, education and resources of the country."
This was about the first indication of a tendency, which grew in
strength for half a century, to load the Federal census with inquiries
having no essential or necessary connexion with its main purpose, which
was to secure an accurate enumeration of the population as a basis for a
reapportionment of seats in the House of Representatives. This tendency
was largely due to a doubt whether the Federal government under the
Constitution possessed the power to initiate general statistical
inquiries, a doubt well expressed in the 9th edition of the
_Encyclopaedia Britannica_ by Francis A. Walker, himself a prominent
member of the party whose contention he states:--

"The reservation by the states of all rights not granted to the
general government makes it fairly a matter of question whether purely
statistical inquiries, other than for the single purpose of
apportioning representation, could be initiated by any other authority
than that of the states themselves. That large party which advocates a
strict and jealous construction of the constitution would certainly
oppose any independent legislation by the national Congress for
providing a registration of births, marriages and deaths, or for
obtaining social and industrial statistics, whether for the
satisfaction of the publicist or for the guidance of the legislature.
Even though the supreme court should decide such legislation to be
within the grant of powers to the general government, the distrust and
opposition, on constitutional grounds, of so large a portion of the
people, could not but go far to defeat the object sought."

The difficulty stated in the foregoing quotation, although now mainly of
historic importance, exerted great influence upon the development of the
American census prior to 1900.

The pioneer work of the census of 1840 in the fields of educational
statistics, statistics of occupations, of defec