204 



There is, therefore, a double inquiry. Why are the 

 degrees of healthiness respectively of some of these towns 

 so nearly alike, or, in fact, identical ? and why again do 

 those of others so remarkably differ ? There must be, there- 

 fore, some general causes, independent of occupations, density 

 of population, poverty of the district, &c., which exercise so 

 material an influence over the duration of life ; and it will be 

 found that the different physical conditions of the inhabitants 

 of each town, depending chiefly upon Geological influences, 

 are such as either generate or make more fatal those peculiar 

 diseases by which the excess of mortality is occasioned. 



Before being able to show how the Geological site of these 

 towns modifies the duration of the life of their inhabitants, 

 and in order to derive all the advantages from the Registrar's 

 Reports already published, it will be necessary to collect 

 and compare the population, the number of deaths, and the 

 peculiar diseases by which the mortality in each town is 

 occasioned. 



As Leeds and Sheffield have the same rates of mortality, 

 the same Geological site, and occupy the extreme point of 

 unhealthiness ; while, on the other hand, Halifax and Hud- 

 dersfield have a Geological locality identical with each other, 

 but differing from Leeds and Sheffield, and are exceedingly 

 healthy towns, the population, deaths, and diseases of the 

 former towns must be compared with those of the latter towns. 



There is, however, considerable difficulty in comparing 

 the diseases and the deaths of Leeds and Sheffield with 

 those of Halifax and Huddersfield, on account of the greater 

 population of the two former towns; and there is left only 

 the choice of making a proportion between the deaths and 

 population of the one, and calculating for the others, or to 

 add some smaller town whose population will bring Halifax 

 and Huddersfield to a standard with Leeds and Sheffield, 

 Both of these modes, however, have been adopted in the 

 following Paper. 



