This paper is a research on the causes of the mortality in England and Wales during the second half of nineteenth century, their évolution and the very large difference between the cities and the country, what is the urban penalty. The difficulty is the measure of the causes of mortality ; we must achieve a most indepth research on the influence of each disease and on the definition of the administrative districts. Therefore, this paper is caracterized by a great methodological effort. To make the research, it was necessary to construct an urban sample -and it is a particularly difficult work, as it is showed in the appendix-, and a rural sample. The research must be continued, but to-day it is clear that the great difference for the adults between cities and countries must be explained by respiratory tuberculosis. As for the gap in the life expectancy, it is always large, because the country has known also an improvement of his mortality.