494 On the Fraitfulncss of Marriages. Bk. ii. 



countries, whatever may be the degree of their 

 mortality. I have now also (1825) added a third 

 table as convenient on account of the custom of 

 decennial enumerations in this and some other 

 countries. It is calculated by the Rev. B. Bridge, 

 of Peter House, Cambridge, and shows the rate 

 of increase, or period of doubling, from the ob- 

 served per-centage increase of any ten years, sup- 

 posing such rate of increase to continue. 



It will be observed that, when the proportion 

 between the births and burials is given, the period 

 of doubling will be shorter, the greater the mor- 

 tality ; because the births as well as deaths are 

 increased 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 T V* According to 

 Table II. the period of doubling will, in this case, 

 be about 36 years. But if we were to keep the 



* 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 illus- 

 trating the subject. 



