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12 case, but one of which examples may be found; and according to this rate it has appeared in a former Lecture that population would probably, in this country, double itself at the least in thirty-five years.

Thirdly, there is the actual rate which occurs in every country under its existing circumstances, and which, at the present time, and in this country, is that of a duplication in forty-nine or ﬁfty years.

With respect to these different rates of increase we may remark, that the first is the most stable of all, and that though its exact quantity is difficult to be ascertained, yet, whatever it is, it is nearly invariable, and, if it can be rightly assumed to give a rate of duplication in ten years at any particular time and place, the same assumption will be equally applicable to all times and places. The second is much less stable, and oscillates between limits widely distant, according to the varieties of different countries in respect of climate, and in the same country at different times, according as it is cleared, drained, and improved, and according to the advance of its inhabitants in the knowledge of medicine, and in their command of the conveniences