406 



THE CLIMATE OF IRELAND, AND 



of the temperature of the hottest month above 50 Fahr., or with 

 the defect of temperature of the coldest "below the same.* 



I believe that this decrease of the mortality, in proceeding 

 from the hotter to the colder parts of Europe, and its subsequent 

 increase, result from fas joint operation of different diseases having 

 opposite relations to temperature. Epidemic and endemic diseases 

 appear to diminish indefinitely, as the temperature diminishes ; 

 while consumption, and other diseases of the respiratory organs, 

 increase. These are the maladies most destructive of human life ; 

 and it will be readily understood in what manner their contrary 

 tendencies may produce a minimum mortality at some temperature 

 far removed from either of the two extremes.! 



I have already stated that the absolute minimum of mortality 

 is to be sought for at the western extremity of the yearly isother- 

 mal of 50 i. e., in our own island ; and the facts bear out this 

 conclusion. The average mortality of Ireland, so far as it can be 



* There is, of course, some uncertainty in comparing numbers, one set of which are 

 dependent on political boundaries, and the other upon physical features. In Russia, 

 the mean winter temperature adopted is that of the January isothermal passing nearly 

 through three of the great centres of population Petersburgh, Moscow, and Astrakhan. 

 No attempt has been made to include Sweden and Norway in the comparison, the 

 extraordinary flexures of the January isothermals in these countries rendering the 

 deduction of a mean winter temperature uncertain. 



t This law appears to be exhibited, even within the narrow limits of our own 

 island. It appears from the valuable statistics of disease collected during the Census, 

 and discussed by Sir W. Wilde, that deaths by consumption are least numerous in the 

 south-west of Ireland, while deaths from epidemic and contagious diseases are most 

 numerous in the same district. 



