a
very hot Day or two has gone before. A less Quantity of the same Matter
remains in the upper Cortex of the Earth for the Month of _June_, but
in the mean Time a Stock arises out of the deeper Bowels of the Earth,
which is attenuated and prepared, so that by the very fervent Heat of
_July_ it is elevated, as it were in heaps, and set on Fire. Hence
Thunder is as frequent in _July_ as in _May_. And the Heat decreasing
in the succeeding Months, the Exhalation of the fulminating Matter out
of the Earth is more sparing, and thence, also, the thunder is less
frequent, till in October, and the other winter months, the earth is
bound up with us, and hardly expires any more. Hence we see why it very
seldom thunders when the northerly winds blow; for these winds
constringe the earth with their cold, and so hinder the fulminating
matter from bursting forth; and when they are burst forth and floating
in the air, they hinder their effervency. But on the contrary, when the
warm and moist south winds blow, which open every thing, the earth
likewise is opened, and abundance of fulminating matter is expired and
ascends on high, which is there easily inflamed.

AS the flame runs very swiftly, it seems to carry along with it
particles, which it could not so easily set on fire, and when any of
these particles are drawn together, and heated to a certain degree,
they at last take fire, with a sudden and great explosion, and thereby
produce what we call a thunder Clap. Now, though this be only a single
sound, yet it is often heard in the form of a great murmuring noise of
a long continuance; sometimes for thirty or forty seconds, because of
its various repercussions by the clouds and terrestrial obstacles.
Hence it is, that in vales, which are surrounded by mountains of a
different Height, there is a terrible and long continued Bellowing of
thunder Claps. Whereas for one Explosion it has been observed that
there is but one Clap. Yet however if the Flame set Fire to two, three,
or more fulmineous Tracts, each of them at last will end in a Clap, and
thus several Sounds may be heard together, or quickly succeeding one
another.

XX.

_If you see a Cloud rise against the Wind or side Wind, when that
Cloud comes up to you, the Wind will blow the same Way that the Cloud
came. And the same Rule holds of a clear Place, when all the Sky is
equally thick, except one clear Edge._

THIS seems to arise from hence, that Wind being nothing more than