Cultivation must have been improving, and marriages, consequently, encouraged.

For the checks to population appear to have been rather of the positive, than of the preventive kind.

When from a prospect of increasing plenty in any country, the weight that represses population is in some degree removed, it is highly probable that the motion will be continued beyond the operation of the cause that first impelled it.

Or, to be more particular, when the increasing produce of a country, and the increasing demand for labour, so far ameliorate the condition of the labourer as greatly to encourage marriage, it is probable that the custom of early marriages will continue till the population of the country has gone beyond the increased produce, and sickly seasons appear to be the natural and necessary consequence.

I should expect, therefore, that those countries where subsistence was increasing sufficiency at times to encourage population but not to answer all its demands, would be more subject to periodical epidemics than those where the population could more completely accommodate itself to the average produce.
An observation the converse of this will probably also be found true.
In those countries that are subject to periodical sicknesses, the increase of population, or the excess of births above the burials, will be greater in the intervals of these periods than is usual, caeteris paribus, in the countries not so much subject to such disorders.