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in 
Experiments on the variable Action of the ElectricColumn, 417 
Experiment 1. Was destined to try whether at equal degrees 
of heat aud moisture in the open air an uniform action prevailed, 
and the result shows that it was very nearly so. 
Experiment 2. Shows that the same uniformity continued 
in the receiver, which was not air-tight, 
Experiment 3. Shows that when the air of the receiver was 
gradually heated from 53 to 70, and by this means the hygro- 
meter made to advance 94 degrees towards dryness, the electro- 
meter increased its strikings progressively from 3°75 to 17 times 
per minute. 
Experiment 4, Proves that the column had not undergone 
@ permanent change by Experiment 3. 
Experiment 5. Shows that when the air of the receiver was 
dried by means of sulphuric acid from 37 to 64, giving for the 
whole diminution of moisture 304 degrees, no increased inten- 
sity took place. 
Experiment 6. Proves that the column had not been pers 
manently affected by the last Experiment. 
Experiment 7. Shows that when the the air was moistened 
56 degrees, the intensity was diminished from 44 strikings per 
minute te a divergence of 48; inch. 
It would be unnecessary and tedious to detail some other 
Experiments which were made with a different view, but which 
conspired with the above to indicate that heat is the principal 
cause of the phenomenon, and that a moist atmosphere pro- 
duces exactly the same effect on the glass tube of the column 
that it does on the insulators in all other electrical experiments. 
It now therefore seems a matter of some interest to resolve 
several queries relative to the mode in which heat acts: for in- 
stance, Does it promote the electromotive powers of the metals? 
Does it produce the effect by giving motion to the combined mois- 
ture of the interposed disks of paper ? or by rendering those disks 
more or less conducting ? Is there any analogy between the column 
andthe tourmalin? The justly celebrated inventor of this modifi- 
cation of the Voltaic pile, having first observed that equal degrees 
of heat and moisture were not accompanied at different times 
with a corresponding intensity of action, conceived that this dif- 
ference was occasioned by changes in the electrical state of the 
ambient air, for which reason he gave it the name of Aérial 
Electroscope, and I think the evidence of our present experience 
preponderates in favour of the conjecture. 
Becearia, Read, and others haye shown that the state of 
moisture of the higher regions of the atmosphere is intimately 
connected with that of its electricity: a height of only six or 
eight feet above the surface of the earth is even sometimes suffi- 
aient for collecting powerful electrie signs in an open situation, 
Vol, 43, No. 194, June 1814, Dd I have 
