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XIX. Experiments and Observations made with the Doubler of 
Electricity, with a view to determine its real Utility , in the in- 
vestigation of the Electricity of atmospheric Air, in different 
degrees of Purity. By Mr. John Read. Communicated by 
Richard Henry Alexander Bennet, Esq. F. R. S. 
Read May 1 5, 1794. 
It is scarcely necessary to observe, that having removed the 
uncertainty respecting the electrical action of this curious 
instrument, by demonstrating (after much care and pains, as 
is particularly expressed in my tract on Spontaneous Electri- 
city) that the electricity of the doubler is alone derived from 
the common electrified aqueous vapour suspended in the air ; 
I shall, without any further explanation, beg leave here to 
express my thoughts in terms according to that dsmonstra- 
tion. . 
When I employ the doubler to investigate atmospheric 
electricity, I use it with its revolving plate uninsulated, when 
opposite to that fixed plate which is insulated ; because, with 
respect to insulation, that position of the doubler exactly 
corresponds to the insulated and uninsulated parts of my high 
pointed rod, and of course their electrical accumulation will 
always be of the same kind in all weak electrifications of the 
atmosphere. To avoid repetition, permit me here also to 
mention, that care has been always taken to clear the doubler 
