after Sir William Petty's death, although he points out in these
essays how easily it could be established, and what useful
information it would give. There was a census taken at Rome 566
years before Christ. But the first census in Great Britain was
taken in 1801, under provision of an Act passed on the last day of
the year 1800, to secure a numbering of the population every ten
years. Ireland was not included in the return; the first census in
Ireland was not until the year 1813.

Sir William Petty had to base his calculations partly upon the Bills
of Mortality, which had been imperfectly begun under Elizabeth, but
fell into disuse, and were revived, as a weekly record of the number
of deaths, beginning on the 29th of October, 1603; notices of
diseases first appeared in them in 1629. The weekly bills were
published every Thursday, and any householder could have them
supplied to him for four shillings a year. These essays will show
how inferences as to the number of the living were drawn from the
number of the dead. And even now our Political Arithmetic depends
too much upon rough calculations made from the death register. It
is seven years since the last census; we have lost count of the
changes in our population to a very great extent, and have to wait
three years before our reckoning can be made sure. The interval
should be reduced to five years.

Another of Sir William Petty's helps in the arithmetic of population
was the Chimney Tax, a revival of the old fumage or hearth-money--
smoke farthings, as the people called them--once paid, according to
Domesday Book, for every chimney in a house. Charles the Second had
set up a chimney tax in the year 1662; the statistics of the
collection were at the service of Sir William Petty. The tax