On the fruitfulness of marriages.

creased by this supposition, and they both bear a greater proportion to the whole population than if the mortality were smaller, and there were a greater number of people in advanced life.

The mortality of Russia, according to Mr. Tooke, is 1 in 58, and the proportion of births 1 in 26. Allowing for the omissions in the burials, if we assume the mortality to be 1 in 52, then the births will be to the deaths as 2 to 1, and the proportion which the excess of births bears to the whole population will be 2. According to Table II. the period of doubling will, in this case, be about 36 years. But if we were to keep the proportion of births to deaths as 2 to 1, and suppose a mortality of 1 in 36, as in Table I. the excess of births above. the burials would be of the whole population, and the period of doubling would be only 25 years.

The proportions here mentioned are different from those which have been taken from the additional table in Mr. Tooke's second edition; but they are assumed here as more easily and clearly illustrating the subject.

When in any country there are 100,000 persons living, and the mortality is 1 in 36.

The proportion of

TABLE II.

The proportion of

the excess of births Periods of doubling the excess of births Periods of doubling above the deaths, in years, and ten above the deaths, in years, and ten to the whole of thousandth parts. ||to the whole of the thousandth parts.

the living.

living.

The proportion of The proportion of the excess of births Periods of doubling the excess of births Periods of doubling above the deaths, in years, and ten above the deaths, in years, and ten to the whole of the thousandth parts. to the whole of the thousandth parts. living.

living.

CHAPTER X.

Effects of Epidemics on Registers of Births, Deaths, and Marriages.

IT appears clearly, from the very valuable tables of mortality which Sussmilch has collected, and which include periods of 50 or 60 years, that all the countries of Europe are subject to periodical sickly seasons, which check their increase; and very few are exempt from those great and wasting plagues, which, once or twice, perhaps, in a century, sweep off the third or fourth part of their inhabitants. The way in which these periods of mortality affect all the general proportions of births, deaths, and marriages, is strikingly illustrated in the tables for Prussia and Lithuania, from the year 1692 to the year 1757.

1 Sussmilch, Gottliche Ordnung, vol. i. table xxi. p. 83, of the tables.