No rain ever falls from the dome itself,
and yet it consists of true clouds."
"I think," he replied, "that the dome is due to vapors which assemble at
a general level of condensation, and do not form raindrops, partly
because of the absence of dust to serve as nuclei at this great height,
and partly because of some peculiar electrical condition of the air,
arising from the relative nearness of Venus to the sun, which prevents
the particles of vapor from gathering into drops heavy enough to fall.
You will observe that there is a peculiar inner circulation in the vapor
surrounding us, marked by ascending and descending currents which are
doubtless limited by the upper and lower surfaces of the dome. The true
rain clouds form in the space beneath the dome, where there seems to be
an independent circulation of the winds."
On entering the cloud vault Edmund had closed the windows, explaining
that it was not merely the humidity which led him to do so, but the
diminishing density of the air which, when we had risen considerably
above the dome, would become too rare for comfortable breathing. In a
little while his conjecture about a peculiar electrical condition was
justified by a pale-blue mist which seemed to fill the air in the car;
but we felt no effects and the mechanism was not disturbed.
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