56-61.
The electric equilibrium is less frequently disturbed where the aerial ocean
rests on a liquid base than where it impends over the land; and it is very
striking to observe how, in extensive seas, small insular groups affect the
condition of the atmosphere, and occasion the formation of storms. In fogs,
and in the commencement of falls of snow, I have seen, in a long series of
observations, the previously permanent positive electricity rapidly pass
into the negative condition, both on the plains of the colder zones, and in
the Paramos of the Cordilleras, at elevations varying from 11,000 to 15,000
feet. The alternate transition was precisly similar to that indicated by
the electrometer shortly before and during a storm.*
[footnote] *Humboldt, 'Relation Historique', t. iii., p. 318. I here only
refer to those of my experiiments in which the three-foot metallic conductor
of Saussure's electrometer was neither moved upward nor downward, nor,
according to Volta's proposal, armed with burning sponge. Those of my
readers who are well acquainted with the 'quaestiones vexatae' of
atmospheric electricity will understand the grounds for this limitation.
Respecting the formation of storms in the tropics, see my 'Rel. Hist.
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