1the ſame water in paſſing under the Bridge, in our caſe meeteth
with eight of the ſame impediments, bearing, and thruſting upon
two ſides of each Arch (to omit the impediment of the bottom,
for that it is the ſame in the River, and under the Bridge) from
which inadvertency ſometimes follow very great diſorders, as
quotidian practice ſhews us.
with eight of the ſame impediments, bearing, and thruſting upon
two ſides of each Arch (to omit the impediment of the bottom,
for that it is the ſame in the River, and under the Bridge) from
which inadvertency ſometimes follow very great diſorders, as
quotidian practice ſhews us.
APPENDIX IX.
It is alſo worthy to conſider the great and admirable benefit
that thoſe fields receive, which are wont to drink up the Rain
water with difficulty, through the height of the water in the
principal Ditches; in which caſe the careful Husbandman cutteth
away the reeds and ruſhes in the Ditches, through which the
waters paſs; whereupon may be preſently ſeen, ſo ſoon as the
reeds and ruſhes are cut, a notable Ebb in the level of the water
in the Ditches; inſomuch that ſometimes it is obſerved, that the
water is abated after the ſaid cutting a third and more, of what it
was before the cutting. The which effect ſeemingly might de
pend on this, That, before thoſe weeds took up room in the
Ditch, and for that cauſe the water kept a higher level, and the
ſaid Plants being afterwards cut and removed, the water came to
abate, poſſeſſing the place that before was occupied by the
weeds: Which opinion, though probable, and at firſt ſight ſa
tisfactory, is nevertheleſs inſufficient to give the total reaſon of
that notable abatement which hath been ſpoken of: But it is ne
ceſſary to have recourſe to our confideration of the velocity in
the courſe of the water, the chiefeſt and true cauſe of the vari
ation of the meaſure of the ſame Running-Water; for, that
multitudes of reeds, weeds, and plants diſperſed through the cur
rent of the Ditch, do chance notably to retard the courſe of the
water, and therefore the meaſure of the water increaſeth; and
thoſe impediments removed, the ſame water gaineth velocity,
and therefore decreaſeth in meaſure, and conſequently in
height.
that thoſe fields receive, which are wont to drink up the Rain
water with difficulty, through the height of the water in the
principal Ditches; in which caſe the careful Husbandman cutteth
away the reeds and ruſhes in the Ditches, through which the
waters paſs; whereupon may be preſently ſeen, ſo ſoon as the
reeds and ruſhes are cut, a notable Ebb in the level of the water
in the Ditches; inſomuch that ſometimes it is obſerved, that the
water is abated after the ſaid cutting a third and more, of what it
was before the cutting. The which effect ſeemingly might de
pend on this, That, before thoſe weeds took up room in the
Ditch, and for that cauſe the water kept a higher level, and the
ſaid Plants being afterwards cut and removed, the water came to
abate, poſſeſſing the place that before was occupied by the
weeds: Which opinion, though probable, and at firſt ſight ſa
tisfactory, is nevertheleſs inſufficient to give the total reaſon of
that notable abatement which hath been ſpoken of: But it is ne
ceſſary to have recourſe to our confideration of the velocity in
the courſe of the water, the chiefeſt and true cauſe of the vari
ation of the meaſure of the ſame Running-Water; for, that
multitudes of reeds, weeds, and plants diſperſed through the cur
rent of the Ditch, do chance notably to retard the courſe of the
water, and therefore the meaſure of the water increaſeth; and
thoſe impediments removed, the ſame water gaineth velocity,
and therefore decreaſeth in meaſure, and conſequently in
height.
And perhaps this point well underſtood, may be of great
profit to the fields adjacent to the Pontine Fens, and I doubt not
but if the River Ninfa, and the other principal Brooks of thoſe
Territories were kept well cleanſed from weeds, their waters
would be at a lower level, and conſequently the drains of the
fields would run into them more readily; it being alwayes to be
held for undoubted, that the meaſure of the water before the
cleanſing, hath the ſame proportion to the meaſure after clean
ſing, that the velocity after the cleanſing hath to the velocity
before the cleanſing: An dbecauſe thoſe weeds being cleanſed
profit to the fields adjacent to the Pontine Fens, and I doubt not
but if the River Ninfa, and the other principal Brooks of thoſe
Territories were kept well cleanſed from weeds, their waters
would be at a lower level, and conſequently the drains of the
fields would run into them more readily; it being alwayes to be
held for undoubted, that the meaſure of the water before the
cleanſing, hath the ſame proportion to the meaſure after clean
ſing, that the velocity after the cleanſing hath to the velocity
before the cleanſing: An dbecauſe thoſe weeds being cleanſed