deg., in the tropics, and of 50 deg. to 55 deg. in
mid-winter here.

Thus far, an adherence to the opinion that condensation was simply a
cooling process; the driving out of its latent heat, not merely to another
body to make an equilibrium, but "_getting rid of it_" by positive active
radiation, or in some other way, so as to cool off and condense, has
involved the formation and classification of clouds in obscurity. Hopkins
(Atmospheric Changes, p. 331) laments this, but fettered by a false and
imperfect theory, in relation to the tension of vapor, he falls into a
similar error.

Now, there are, as we have seen, peculiar, distinctly-marked varieties of
cloud, connected with peculiar and distinctly-marked conditions of the
atmosphere, _irrespective of temperature_. None of the theories advanced,
account, or profess to account for the differences in either. No
modification of the calorific theory will account for them. They differ in
shape, in color, in tendency to precipitation, in line of progress, and in
electrical character. The explanation of this is found in the fact, that
they form in distinct and different strata, partake of the positive
electric character of the one, or the negative of the other; or are
secondary, induced by the action of a primary condensation in a different
stratum. There is not any mingling of the different strata, as has been
supposed; and many other facts than those to which we have alluded, show
that the formation of cloud is a magneto-electric process.

The observations of Reid show that every violent shower cloud has the
electricities disturbed, and portions of it are positive, and others
negative. Howard gives us the following _resume_ of Reid's observations:

"From an attentive examination of Reid's observations I have been
able to deduce the following general results:

"1. _The positive electricity, common to fair weather, often yields
to a negative state before rain._

"2. _In general, the rain that first falls, after a depression of the
barometer, is_ NEGATIVE.

"3. _Above forty cases of rain, in one hundred, give negative_
electricity; although the state of the atmosphere is positive, before
and afterward.

"4. _Positive rain, in a positive atmosphere, occurs more rarely_:
perhaps fifteen times in one hundred.

"5. _Snow and hail, unmixed with rain, are positive, almost without
exception._

"6. _Near