ith another. Therefore Thunder seems now to run horizontally, now from
above downwards, now upwards from the Earth, for if the Matter of
Thunder pressing out of the Earth is enflamed near the Ground, the
Flame darting upwards, the Thunder will seem to be projected out of the
Earth. If the same Tract be set on Fire at its upper end, the Flame
will move downwards, and the Thunder will seem to descend out of the
Sky.

HENCE we easily understand how it comes to thunder oftener in one Place
than another, but most frequently in those where the Soil produces
odoriferous Herbs, and abounds with Sulphur, and where the People are
much exposed to the extreme Heat of the Sun. Thunder is less frequent
in Places where there are few odoriferous Herbs, very little Sulphur,
or where the Climate is watery and moist. For Instance, it thunders
very much in _Italy_ and _Sicily_, and very rarely in _Egypt_, and the
adjacent Countries. If it be demanded how it comes to thunder in the
midst of the Ocean? The Answer is easy, because from the Bottom of the
Ocean vast Tracts of sulphureous Matter are cast up through the Waters;
as it happens to spring Waters in several Places, the Streams of which
will take Fire from a lighted Candle. For sulphureous Exhalations
bursting out together with the Waters, the fulmineous Matter in the Air
is set on Fire when it meets with Exhalations or Vapours with which it
can excite a vehement Effervescence. It is very clear from this
Account, that the Clouds mentioned at the Top of the twenty-eighth Page
are thunder Clouds, or Clouds big with the Materials of Thunder.

XIX.

_If two such Clouds arise, one on either Hand_, it is Time to make
haste to shelter.

AS this Observation is of the same Nature with the former, we shall
continue our Remarks. The Reason why it seldom thunders in Winter is,
because the exterior Parts of the Earth are so contracted by the cold
Snow and Ice, that Sulphur cannot perspire in any great Quantities, but
as soon as the Earth begins to be opened by the Sun in the Spring,
something expires in the Month of _April_ which takes Fire. But by the
greater Heat of the Sun penetrating deeper into the Earth, the Cortex
is more opened in _May_, and now there is a more copious Expiration of
the fulminating Matter, and whatever was collected and shut up in
Winter, is now released and snatched up in the Air, and thence proceeds
the most frequent Thunders in the Month of _May_, and chiefly when