PROCEEDINGS 
or 
THE ROYAL IRISH ACADEMY, 
1839. No. 20. 
December 9. 
SIR Wm. 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 
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