680 PHILOSOPHICAL TRANSACTIONS. [aNNO 1775. 



therefore 1 in 21-J- died annually. In London, at least 1 in 20|- of the inhabi- 

 tants die annually. And, from a particular survey and a very accurate register 

 of mortality at Northampton, it appears that 1 in 264- die there annually. 



Let these facts be compared with the following. In 1767, a survey was made 

 of the inhabitants of the island of Madeira, under the direction of Dr. Thomas 

 Heberden, and their number was found to be 64(J14. The average of burials 

 for 8 preceding years had been 1293. Only 1 in 50 therefore of the inhabitants 

 died annually. 



The district of Vaud, in Switzerland, in 1766, contained 1 12951 inhabitants. 

 The average of deaths for 10 preceding years had been 2504. Only 1 in 45 

 therefore died annually. The number of inhabitants in the parish of Ackworth, 

 in the county of York, in I737j was 603 ; and the average of deaths for 10 

 years had been 10-rV) or a 56th part. In 1767, the inhabitants were increased 

 to 728 ; and the annual average of deaths was IS-jij^, or nearly a 47th part. 



The reason of this striking difference between the rate of human mortality in 

 towns and in country parishes and villages must be, first, the luxury and the 

 irregular modes of life which prevail in towns ; and, secondly, the foulness of 

 the air. But it has been inquired, whether the migrations of people from the 

 country to towns may not produce this difference, by lessening the proportion of 

 inhabitants that die in the country, and increasing the same proportion in towns ? 

 In answer to this inquiry, Dr. P. observes, 1st, that this difference, being a dif- 

 ference of near a half, it is apparently much greater than can be accounted for 

 by any such cause. But 2dly, it should be considered, that if migrations lessen 

 the number of deaths, they also lessen the number of inhabitants ; and that it 

 depends entirely on the ages at which the inhabitants remove from a place, whe- 

 ther the effect of their removal shall be lowering or raising the proportion of the 

 annual deaths to the number of inhabitants. In the present case, the truth af>- 

 pears to be, that the most common age of migration from the country, is such 

 as raises this proportion in the country. This will be evident from the following 

 considerations. The period of life in which persons remove from the country 

 to settle in towns, is chiefly the beginning of mature life, or from the age of 

 10 or 15 to 25 or 30. In infancy none migrate; and in the decline of life, it 

 is more usual to retire from towns than to remove to them. Towns therefore 

 will be inhabited more by people in the firmest parts of life ; and, on the other 

 hand, the country will be inhabited more by people in the weakest parts of life ; 

 and the consequence of this is, that in the country, the inhabitants must die 

 faster in proportion to their number than they otherwise would, and that in 

 towns they must die more slowly. In particular, the number of children is 

 always much greater in the country than in towns ; and this is a circumstance 

 which must be extremely unfavourable to the former : for it is well known, that 



