414 



April 27. 



SIR Wm. R. HAMILTON, LL.D., President, in the Chair. 



His Grace the Archbishop of DubHn gave a verbal ac- 

 count of some observations which he had made upon the 

 weather, in connexion with the prognostic drawn from the 

 variations of atmospheric pressure, as indicated by the baro- 

 meter. The sudden changes of the barometer, his Grace 

 observed, were well known to be connected with correspond- 

 ing changes of the weather as to rain or drought, and the 

 great and rapid falls with the sudden approach of a gale of 

 wind ; but it did not seem to be so generally remarked, that 

 the slow and continuous changes of the height of the mercury 

 in the barometer were likewise indications of the approach 

 of a season of long continued wet or dryness. It was to some 

 connexions of this latter kind, noticed by himself, that he 

 now drew the attention of the Academy. The first of 

 these occurred in the early part of the summer of 1818, when, 

 fromthe slow and gradual rise of the barometer for the space of 

 ten days, he was led to predict the approach of a long continued 

 dry season. The drought which followed was one of the most 

 remarkable that had occurred in this climate for many years. 

 The second instance of the same kind observed by his Grace 

 was in the early part of the spring of the present year. On 

 the 17th of February the barometer commenced to rise, but 

 very slowly, and the rise continued for six or seven days ; he 

 was thus led to expect a long continuance of dry weather ; 

 and the result, as is well known, fully verified the anticipa- 

 tion, the change being followed by more than three weeks, 

 during which there was not a single drop of rain, and that 

 too at a season of the year usually wet. 



The Secretary read a notice by Mr. George Knox on the 



