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32 EFFECTS OF DENUDATION. [Ch. III. 
If, for example, all the registers are made in a single year, 
the proportion of deaths and births will be so small during 
the interval between the compiling of two consecutive docu- 
ments, that the individuals described in each will be nearly 
identical ; whereas, if there are sixty provinces, and the survey 
of each requires a year, there will be an almost entire discord- 
ance between the persons enumerated in two consecutive regis- 
ters. 
There are undoubtedly some other causes besides the mere 
quantity of time which may augment or diminish the amount 
of discrepancy. Thus, for example, at some periods a pesti- 
lential disease may lessen the average duration of human life, 
or a variety of circumstances may cause the births to be 
unusually numerous, and the population to multiply ; or, a pro- 
vince may be suddenly colonized by persons migrating from 
surrounding districts. 
We must also remind the reader, that we do not propose the 
above case as an exact parallel to those geological phenomena 
which we desire to illustrate ; for the commissioners are sup- 
posed 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 
another, 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 of some of the statistical 
documents before mentioned. It is evident, that where such 
accidents occur, the want of continuity in the series may be- 
come indefinitely great, and that the monuments which follow 
next in succession will by no means be equidistant from each 
other in point of time. 
If this train of reasoning be admitted, the frequent distinct- 
ness of the fossil remains, in formations immediately in contact, 
would be a necessary consequence of the existing laws of 
