1made it a perfect Marſh, like Arabia, which
by means of a Number of Lakes and Bogs oc
caſioned by the River Euphrates, was not to
be approached by an Enemy. Thus by ſuch
Fortifications they both ſecured their own
Country againſt the Attacks of an Enemy, and
at the ſame Time made their Enemy's Coun
try weaker and more defenceleſs. What are
the Cauſes which make the Air unhealthy, we
have already ſhewn ſufficiently at Length in
the proper Place. We may only obſerve here
in general, that for the moſt Part thoſe Cauſes
are either the too great Power of the Sun, or
too much Shade; ſome infectious Winds from
neighbouring Parts, or peſtilent Vapours from
the Soil itſelf, or elſe ſomething in the very
Climate itſelf that is noxious. To mend the
Air when it is unhealthy or corrupted, is a
Work ſcarce thought poſſible to be done by any
human Contrivance; unleſs by appeaſing the
Wrath of Heaven by Prayers and Supplications,
which, like the Nail driven by the Conſul, have
ſometimes, as we read, put a Stop to the moſt
deſtructive Contagions. Againſt the Inconve
niencies of the Sun or Wind to the Inhabitants
of ſome little Town or Villa, perhaps ſome
Remedy may be found: But to alter the Cli
mate of a whole Region or Province, is a Task
too great; not that I deny the Poſſibility of
amending a great many of thoſe Defects which
proceed from the Air, by curing the Earth of
exhaling noxious Vapours. In order to ſhew
how this may be done, it is not neceſſary that
I ſhould here ſpend Time in debating whether
it is by means of the Power of the Sun, or by
ſome natural inward Heat, that the Earth emits
thoſe two Vapours, of which one mounting up
into the Air is condenſed by the Cold, into
Rain and Snow; and the other, which is a dry
Vapour, is ſuppoſed to be the Cauſe of Winds:
It is enough that we are aſſured, that both theſe
ariſe out of the Earth; and as we find that
thoſe Steams which proceed from the Bodies
of Animals, partake of the Nature of the Bodies
from which they ariſe, peſtiferous from peſti
lentious Bodies, and ſweet from wholeſome and
cleanly ones, and that ſometimes where the
Sweat or Vapour is not bad in itſelf, it is ren
dered offenſive by the Naſtineſs of the Gar
ment through which it paſſes; ſo it is with the
Earth: For when the Ground is neither well
covered with Water, nor perfectly dry, but lies
like a Marſh or Bog, it muſt for ſeveral Rea
ſons emit noxious and unwholeſome Vapours.
Thus we find, that where the Sea is deep, the
Water is cold, and warm where it is ſhallow;
the Reaſon of which, we are told, is becauſe
the Rays of the Sun cannot ſtrike to the Bot
tom of a deep Water: As if you plunge a red
hot Iron into Oil, if the Oil be but a ſmall
Quantity, it will raiſe a ſtrong thick Smoke,
but if there is Oil enough to cover it quite over,
it will preſently quench the Iron, and make
no Smoke at all. But to proceed briefly with
the Subject which we have begun to take
in Hand. Servius tells us, that a Marſh near
a certain Town being almoſt dried up, and a
Plague ſucceeding, the Inhabitants went for
Counſel to Apollo, who commanded them to
dry it up entirely. Near Tempe, there was a
large ſtanding Lake, which Hercules made dry
Ground, by cutting a Trench to let out the
Water, and he is ſaid to have burnt the Ser
pent Hydra in a Place from whence frequent
Eruptions of Water uſed to ravage the neigh
bouring City; by which means the ſuperfluous
Moiſture being conſumed, and the Soil render
ed firm and dry, thoſe over-abounding Chan
nels of Water were entirely ſtopt. In ancient
Times the Nile having once ſwelled higher
than uſual, when the Waters went off, beſides
the Mud, they left a great Number of different
Animals, which as the Ground became dry,
rotted and infected the Air with a dreadful
Plague. Strabo ſays, that the City Mazaca,
near the Hill Argæus, abounds in good Wa
ter; but if in Summer it has not a Way made
for it to run off, it renders the Air unwhole
ſome and infectious. Moreover, towards the
northern Parts of Africa, and alſo in Æthiopia,
it never Rains; ſo that the Lakes are often
dried up, and left like Bogs of Mud, abounding
with infinite Numbers of Animals that breed
by Corruption, and particularly with great
Swarms of Locuſts. Againſt theſe Inconveni
encies, both the Remedies uſed by Hercules are
very proper, namely, cutting a Trench that the
Water may not ſtagnate and make a Bog, and
then laying the Ground open to the Sun,
which I take to be the Fire uſed by Hercules
for burning the Hydra. It may alſo be of Ser
vice to fill up the Place with Stones, Earth or
Sand: And in what Manner you may fill up a
ſtanding Water with River-ſand, we ſhall ſhew
in the proper Place. Strabo ſays, that in his
Time the Country about the City of Ravenna,
being continually overflowed by the Sea, uſed
to be incommoded with noiſome Vapours,
which yet did not make the Air unwholeſome,
and it ſeems ſtrange how this ſhould happen,
by means of a Number of Lakes and Bogs oc
caſioned by the River Euphrates, was not to
be approached by an Enemy. Thus by ſuch
Fortifications they both ſecured their own
Country againſt the Attacks of an Enemy, and
at the ſame Time made their Enemy's Coun
try weaker and more defenceleſs. What are
the Cauſes which make the Air unhealthy, we
have already ſhewn ſufficiently at Length in
the proper Place. We may only obſerve here
in general, that for the moſt Part thoſe Cauſes
are either the too great Power of the Sun, or
too much Shade; ſome infectious Winds from
neighbouring Parts, or peſtilent Vapours from
the Soil itſelf, or elſe ſomething in the very
Climate itſelf that is noxious. To mend the
Air when it is unhealthy or corrupted, is a
Work ſcarce thought poſſible to be done by any
human Contrivance; unleſs by appeaſing the
Wrath of Heaven by Prayers and Supplications,
which, like the Nail driven by the Conſul, have
ſometimes, as we read, put a Stop to the moſt
deſtructive Contagions. Againſt the Inconve
niencies of the Sun or Wind to the Inhabitants
of ſome little Town or Villa, perhaps ſome
Remedy may be found: But to alter the Cli
mate of a whole Region or Province, is a Task
too great; not that I deny the Poſſibility of
amending a great many of thoſe Defects which
proceed from the Air, by curing the Earth of
exhaling noxious Vapours. In order to ſhew
how this may be done, it is not neceſſary that
I ſhould here ſpend Time in debating whether
it is by means of the Power of the Sun, or by
ſome natural inward Heat, that the Earth emits
thoſe two Vapours, of which one mounting up
into the Air is condenſed by the Cold, into
Rain and Snow; and the other, which is a dry
Vapour, is ſuppoſed to be the Cauſe of Winds:
It is enough that we are aſſured, that both theſe
ariſe out of the Earth; and as we find that
thoſe Steams which proceed from the Bodies
of Animals, partake of the Nature of the Bodies
from which they ariſe, peſtiferous from peſti
lentious Bodies, and ſweet from wholeſome and
cleanly ones, and that ſometimes where the
Sweat or Vapour is not bad in itſelf, it is ren
dered offenſive by the Naſtineſs of the Gar
ment through which it paſſes; ſo it is with the
Earth: For when the Ground is neither well
covered with Water, nor perfectly dry, but lies
like a Marſh or Bog, it muſt for ſeveral Rea
ſons emit noxious and unwholeſome Vapours.
Thus we find, that where the Sea is deep, the
Water is cold, and warm where it is ſhallow;
the Reaſon of which, we are told, is becauſe
the Rays of the Sun cannot ſtrike to the Bot
tom of a deep Water: As if you plunge a red
hot Iron into Oil, if the Oil be but a ſmall
Quantity, it will raiſe a ſtrong thick Smoke,
but if there is Oil enough to cover it quite over,
it will preſently quench the Iron, and make
no Smoke at all. But to proceed briefly with
the Subject which we have begun to take
in Hand. Servius tells us, that a Marſh near
a certain Town being almoſt dried up, and a
Plague ſucceeding, the Inhabitants went for
Counſel to Apollo, who commanded them to
dry it up entirely. Near Tempe, there was a
large ſtanding Lake, which Hercules made dry
Ground, by cutting a Trench to let out the
Water, and he is ſaid to have burnt the Ser
pent Hydra in a Place from whence frequent
Eruptions of Water uſed to ravage the neigh
bouring City; by which means the ſuperfluous
Moiſture being conſumed, and the Soil render
ed firm and dry, thoſe over-abounding Chan
nels of Water were entirely ſtopt. In ancient
Times the Nile having once ſwelled higher
than uſual, when the Waters went off, beſides
the Mud, they left a great Number of different
Animals, which as the Ground became dry,
rotted and infected the Air with a dreadful
Plague. Strabo ſays, that the City Mazaca,
near the Hill Argæus, abounds in good Wa
ter; but if in Summer it has not a Way made
for it to run off, it renders the Air unwhole
ſome and infectious. Moreover, towards the
northern Parts of Africa, and alſo in Æthiopia,
it never Rains; ſo that the Lakes are often
dried up, and left like Bogs of Mud, abounding
with infinite Numbers of Animals that breed
by Corruption, and particularly with great
Swarms of Locuſts. Againſt theſe Inconveni
encies, both the Remedies uſed by Hercules are
very proper, namely, cutting a Trench that the
Water may not ſtagnate and make a Bog, and
then laying the Ground open to the Sun,
which I take to be the Fire uſed by Hercules
for burning the Hydra. It may alſo be of Ser
vice to fill up the Place with Stones, Earth or
Sand: And in what Manner you may fill up a
ſtanding Water with River-ſand, we ſhall ſhew
in the proper Place. Strabo ſays, that in his
Time the Country about the City of Ravenna,
being continually overflowed by the Sea, uſed
to be incommoded with noiſome Vapours,
which yet did not make the Air unwholeſome,
and it ſeems ſtrange how this ſhould happen,