Sixteen will live to a hundred.

And only two persons out of the hundred thousand--like the last barks of an innumerable convoy, will reach the advanced and helpless age of a hundred and five years.
Two things are very obvious,--the uncertainty as to the hour of death in individuals, but the regularity and constancy of the circumstances which influence the duration of human life in the aggregate.

It is a matter of certainty that the _average_ life of all persons born in this country extends to about forty-five years.

This has been proved by a very large number of observations of human life and its duration.
Equally extensive observations have been made as to the average number of persons of various ages who die yearly.

It is always the number of the experiments which gives the law of the probability.