402 THE CLIMATE OF IRELAND, AND 



or scarcity of the years in question.* The comparison has been 

 made by Mr. Whitley, of Truro, in Cornwall, and the result 

 which he has obtained from it is interesting and important. 



The observations of temperature to which I refer were begun 

 in the year 1774, and were continued (with only an interruption 

 of five years) to the year 1842, inclusive ; they thus extend through 

 sixty-four years. They have been carefully reduced by Mr. 

 Grlaisher, and the means of each month and season computed. 

 One of the results which may be inferred from them and it is 

 a result of some interest in connexion with the effects of season 

 is that, for the most part, the spring and summer of the same 

 year are of the same character, either both above, or both below 

 the mean. In the course of the sixty-four years, the character of 

 the two seasons was the same forty-six times, and opposite only 

 eighteen times ; so that the chances that a warm summer will 

 follow a warm spring, or vice versa, are as two and a-half to one. 



A like fact appears also from Dr. Butty's observations of the 

 weather in Dublin, which extended through forty-one years in 

 the last century (1725-1765). In these observations the character 

 of each season is defined, with reference to the rain-fall, as dry, 

 wet, or variable. The observations have been discussed by Kirwan ; 

 and it appears from that discussion, that wet springs are followed 

 by wet summers five times out of six. 



But to return to the London observations the greatest devia- 

 tion of any particular year, from the mean of all, was 4'8 in defect ; 

 it occurred in the year 1816, which was a year of famine. In 

 the course of the sixty-four years, a deviation of 2, and upwards, 

 occurred twenty-three times, the summer temperature being thirteen 

 times above the mean to that amount, and ten times below it. IS ow it 

 is deserving of notice, that there is no appearance of a regular cycle 

 in these good or bad years, such as Luke Howard and many other 

 meteorologists have imagined. On the contrary, both the warm 

 nnd the cold seasons usually occur in groups, comprising three or 

 four years in succession ; and the groups themselves do not recur 



* It is not, of course, meant that prices furnish an accurate measure of the abund- 

 ance or scarcity of the crop ; for they are dependent, we know, on other causes also, 

 ;imong which legislative enactments regulating the import of foreign grain are the 

 principal. It is enough for the argument in the text, that prices varied with abundant 

 or scanty harvests, as with their principal cause ; and this we know to have been the 

 fact, as long as any restriction on the import of com remained. 



