diately made on the same plan,
and then another, there will, at last, be a series of statistical
documents in each province. When those belonging to any one province
are arranged in chronological order, the contents of such as stand next
to each other will differ according to the length of the intervals of
time between the taking of each census. If, for example, there are sixty
provinces, and all the registers are made in a single year, and renewed
annually, the number of births and deaths will be so small, in
proportion to the whole of the inhabitants, during the interval between
the compiling of the two consecutive documents, that the individuals
described in such documents will be nearly identical; whereas, if the
survey of each of the sixty provinces occupies all the commissioners for
a whole year, so that they are unable to revisit the same place until
the expiration of sixty years, there will then be an almost entire
discordance between the persons enumerated in two consecutive registers
in the same province. There are, undoubtedly, other causes besides the
mere quantity of time, which may augment or diminish the amount of
discrepancy. Thus, at some periods a pestilential disease may have
lessened the average duration of human life, or a variety of
circumstances may have caused the births to be unusually numerous, and
the population to multiply; or, a province may be suddenly colonized by
persons migrating from surrounding districts.

These exceptions may be compared to the accelerated rate of fluctuation
in the fauna and flora of a particular region, in which the climate and
physical geography may be undergoing an extraordinary degree of
alteration.

But I must remind the reader, that the case above proposed has no
pretensions to be regarded as an exact parallel to the geological
phenomena which I desire to illustrate; for the commissioners are
supposed to visit the different provinces in rotation; whereas the
commemorating processes by which organic remains become fossilized,
although they are always shifting from one area to the other, are yet
very irregular in their movements. They may abandon and revisit many
spaces again and again before they once approach another district; and,
besides this source of irregularity, it may often happen that, while the
depositing process is suspended, denudation may take place, which may be
compared to the occasional destruction by fire or other causes of some
of the statist