PROCEEDINGS 



THE ROYAL IRISH ACADEMY. 



1839. No. 20. 



December 9. 

 SIRWm. R. HAMILTON, LL.D., President, in the Chair. 



Mr. Clarke read a supplement to his paper " on Atmos- 

 pheric Electricity." 



The author gave in this supplement a more detailed 

 description than he had before done of the mode of insu- 

 lating the apparatus for experiments on atmospheric elec- 

 tricity, which he had used in the course of his recent 

 researches. 



He then described an experiment by which he had 

 shown the absence of decomposing agency in the electricity 

 of serene weather, and stated his opinion of the cause. 



Mr. Clarke next directed attention to the fact, that the 

 curve representing the diurnal variation of the barometric 

 column was the reverse of the electric, thermometric, and 

 hygrometric curves. He considered that such a result was 

 to be expected ; for the barometric column should naturally 

 be lower from mid-day to 3 p. m. than at midnight, in conse- 

 quence of the greater quantity of aqueous vapour which ex- 

 ists in the atmosphere at the former than at the latter 

 time, — air charged with aqueous vapour being known to be 



2 k 



