408 



THE CLIMATE OF IRELAND, AND 



burials in Dublin was greatest in March, and least in October and 

 November; and in Ireland generally the mortality is greatest in 

 spring, and least in autumn. The following numbers represent 

 the relative mortality at each of the four seasons, that of the entire 

 year being taken, as before, as unity : 



Even for places under the same isothermal line, and at the same 

 season of the year, the difference between the temperatures of day 

 and night, or the diurnal range, exerts an effect upon health. When 

 it is great, the extremes are, of course, more divergent. But, in- 

 dependently of this circumstance, the suddenness of the change of 

 temperature very probably adds to its influence, especially in the 

 case of individuals predisposed to lung-disease. I have already 

 pointed out the fact that, in islands this variation is small, com- 

 pared with the interior of continents. Throughout Ireland, the 

 diurnal range of temperature is small. It is less on the coast than 

 in the interior of the island ; and it is least of all on the coast of 

 Kerry, in the neighbourhood of Valentia, Now it is remarkable 

 that this region is also that most favoured by a high winter tem- 

 perature. The mean direction of the isothermal lines in Ireland, 

 in the winter months, is N. 40 W. ; so that the highest winter 

 temperature is at the south-western extremity of the island, and 

 the lowest at the north-eastern. The former, therefore, seems to 

 be the region most favourable to the patients I have referred to, 

 as well on account of its high winter temperature, as because of 

 its small daily range ; while the latter is the least so. 



This conclusion (which I ventured to advance some years ago, 

 before the facts were known) has since been fully verified by Sir 

 William Wilde, in his analysis of the Census of 1851. Neglecting 

 the inland districts, for which the meteorological data are insuffi- 

 cient, he finds that the deaths from consumption, at the several 



