THE CLIMATE OF IRELAND. 251 



operations of temperature always escaped my cal- 

 culations.' 



" It may be predicted that when the limits of 

 species have been drawn with some exactness for 

 Central and Northern Europe, the regions from which 

 Decandolle took his examples, they will be found to 

 coincide with no mere temperature lines, however 

 calculated and determined, inasmuch as there are 

 much greater differences in the climates of this 

 region than are generally supposed, as regards the 

 rainfall, particularly in the manner of its distribution 

 over the year." l 



The practical result of these views seems to be 

 that the same summer temperature (I mean the 

 average temperature of each twenty-four hours) may 

 be arrived at in two ways : 



(1.) By cool days and warm nights ; or (2) by 

 hot days and cold nights. Hot days are necessary 

 for the growth of good corn crops, and if the days 

 are hot and sunshiny, cold nights are of less import- 

 ance. There is no doubt that the moisture and 

 clouds in the atmosphere of Ireland cause cool days, 

 with little sunshine ; and though the nights are 

 mild, that does not, for the purpose of corn-growing, 

 make up for the want of heat and sunshine by day. 



Dr. Lloyd, the Provost of Trinity College, Dublin, 

 who is probably the best authority we have on the 



1 "Transactions and Proceedings of the Botanical Society of 

 Edinburgh," vol. xi. Part II., 1873, pp. 262-264. 



