We here find that in the 14 counties where proportionate mortality has been the least, the 184 deaths in 10,000 persons are made up by the 297 births; hence 113, or more than 1 per cent., is added by new births to the existing population. In the 14 intermediate counties where the deaths on every 10,000 persons increase to 208, there the deaths are again made up by 302 births, and 94, or close upon 1 per cent., are again added to the population. In the 14 counties where the increase of the population is the greatest, the deaths in every 10,000 persons are increased to 259, but here also we find that the births are again sufficient to make up for the deaths; they are 348, and increase the population by 89, or less than 1 per cent. Hence, if the number of births in each 10,000 persons of the 14 counties where the mortality has been the greatest had taken place amongst every 10,000 persons of the counties where the mortality has been the least, then the increase of population in these latter by births, instead of being 113, would have been 164.[27] I must again observe that the registration of births in the most populous town districts, where the mortality is greatest, is the least perfect. The excess of births over deaths may really be taken to be greater than shown in the returns from the districts where the mortality is the greatest. The estimated increase of population in England in the year 1840, as compared with 1839, is 190,460. In the same period it appears that the births exceeded the deaths by 143,178. The difference between these two amounts, or 47,282, may be considered as the extent of emigration to England, together with the cases of births not registered. To whatever extent emigration takes place from England, there must of course have been a proportionate immigration from other places to make up the increase of population beyond the apparent increase from births. It is observed in some of the worst conditioned of the town districts that the positive numbers of the natives of the aboriginal stock continually diminishes, and that the vacancy as well as the increase is made up by immigration from the healthier district. In a late enumeration of the settled inhabitants of the labouring classes in the lower parts of Westminster, it appeared that not more than one-third of them were natives of London. If inquiry had been made as to whether their parents were natives, it would probably have been found that still fewer had inhabited the district for more than one generation. Simple enumerations of the numbers of a population are of themselves but imperfect means for judging of its progression in strength. That is best shown in the increased proportions of the adults, who are of the age and strength and skill for productive industry, in the extended period during which each adult labourer occupies his post.