New-York daily tribune., 1859-01-28

more than this, and should, consequently, be pro-
yided with more secure protection. We Will
compare the two, and also consider the barrier
inclosing the original receiving reservoir in Central
Park, in the course of this notice.
In the French. school of bridges and highways
(Ecoie DE-, Points ct ChaHsstes three modes are re-
cognized Of constructing tue embsnkments OF reser-
voirs, viz: earth embankmen's alone, wall alone,
and an earth embankment within wall. The great
reservoir of Chsriy, constructed BY the first pan,
is 5000 feet in length with depth OF over -
feet Of water, and so exposed that waves ten feet
il hight have been seen upon it. The width OF the
earth embellishments at top Is given at from lo.4 10
10 &c feet g 10 meters and the slope q. from Ii
TO base for ] vertical oftea being determined BY
the slope which the materials employed are found
TO take after lying for some time piled up In wet
state. The slope on the water side Is faced with
stone, either laid in courses, or rough work, or
sometimes on very fiat slopes, with covering OF
loose, broken stones. Slopes of 45o and from that
10 II 10 have no. stood well at the Canal du
Centre when carried up about 40 feet vertical
hight, and have consequently been protected with
These slope walls are never intended as support
10 the bank but merely to protect them from the
wearing action Of the water aud of the waves. In
constructing the embankments, especial csre is
given to the selection Of the material and the man.
ner Of using il. The earths selected are OF cayey
nature, "terres crassesr the best are at the same
time argillsceous and sandy. When these are not
.l-a nd Iobt
poyed central dyke Of clayey earth is built up IN
tie center, and rhe directions are to emoody THIS
we'll with the solid material at the bottom. Ii the
natural earth too clayey SO as to crack in dry
ing, they are to be mixed with sand to temper
them The material is to be laid in beds, each three
to four inches thick, aud every layer by rolling with
q heavy channeed rollers or by rammng, is to be
thoroughly incorporated with the ono beneath'
| Earth embankments thus made are considered
preferable to walls, on account Of their stability on
almost any ground, while walls must be bedded on
solid foundations. Considered in respect to idper-
nesbilty the walls are said TO possess this property
DO better thar embankments Of the proportionats
thickness; and as the latter spread out TO great
width, they ma s/be regarded as opposing greater
! obstabe to the passage Of water If the effect oil
waves is feared, or injury from sudden drawing
down of the water, the effect OF which is to pro-
duce a tendency in the saturated layers next toe
slope to press in, walls are more secure. But IN
respect TO the changes brought about by degrada
ton in long periods, entertainments require no To-
pairs ia their interior, the materials ever becoming
more solid by settling, while in the walls OF ma
sonny cavities are produced that cannot be reached
without great difficulty, and are uncertain and
costly to repair. The mixed system adopted at
Saint Fereol, and at Couson, is not approved, on
account Of The additional expense it involves with
out corresponding advantages.
The embankment at the new reservoir is con-
structed exactly according to the plans recon-
mended by the French engineers and approved oy
the English authorities on this subject; and the
only objection that be brought against 1t IS IN
que stioniDg the quality of the materials used The
thickness Of the dyke at top is 10 feet inches and
its slope II base TO | vertical both on the inner
ard outer side. At water line the thickness OF
earth is "a feet inches at 80 feet below it is ia
feet inches, and next the water from the top to
solid foundation il is faced with dry wall Is
inches thick of stones set edge and well wedged,
backed with layer of stone inches in thickness,
the pieces broken in sizes to pass through 2inch
ring. This will prevent the penetration of the
smallest water animals that can inlure the embank
ment by their excavations. In the center of this
embankment puddle wall OF clay is built up 10
feet in width, the upper portion, which reaches
above the water line, taperDg of to feet In width
TIE material is selected from the great excavation,
where sufficient clay of excellent quality for
this purpose is found. Specimens are continually
subjected to trial, and none is employed but what
is found to have the proper tenacity. The
foundation Of this bank is a bed of concrete laid
upon the solid rock the surface Of which is usually 2
below the level of the base of the other portion Of
the embankment, and this central rib is thus stayed
by the depth of natural earth excavated for it.
Between the puddle bank and the water the mate
rial is also selected with care TO avoid any quality
Of sand that may when wet, be Of the nature of
quick sand, and even in the outer side none is ad-
mitted that is decidedly of this character The
banks which have been exposed to the recent heavy
rsins show no tendency to gully, as they certainly
would do if quicksaLd were present The layers
are rolled and incorporated together as material is
laid on enough 10 add inches TO the hight, the
roller used being q channeled cast iron machine OF
5000 pounds weight. The reservoir is divided into
/ two nearly equal parts by division wall con-
| structed in similar msnner to the outer embank-
ment, except thst il is faced on both slopes with
stone, and its puddle wall is founded between two
rous of sheet niino irvan ,ioyn To the rock or 70