Evening star. [volume] (Washington, D.C.) 1854-1972, 1886-05-06

defeat. When ali the members were worn out
an adjournment was taken.
The Water Works Extension.
CAPT. HoxIEs TESTIMONY CONTINUED DIS
TINGUISHED AUTHORITIES QUOTED IN SUP
PORT OF HIS VIEWS.
The examination Of Captain Hoxie was con-
tinued before the House subcommittee having
charge of the water works extension question
yesterday, and he brought forward strong
array of facts and authorities to sustain his
position as to the proper mode Of constructing
the extension tunnel, and to show that a con-
crete lining is the only safe one.
Capt. Hoxie quoted number of standard
authorities in support of his views, among them
Gen. Totten on "Mortars and Concretes," who
says: "In constructing with concrete the inte-
ness we may be certain of their great dura-
bility. In rubble or regular masonry the NOR
tar does not always unite itself perfectly to the
stone, SO that it there be a head of water it will
ut least Ind passage between the joints. This
cannot happen In masonry made OF small ma
terals, as concrete, because all OF these small
stones are separated from each other by por-
ton of the mortar which will oppose filtration.
In the two baterdeaux Of Strasburg which
have cited, the facings were displaced, but the
central mass of concrete prevented u single drop
OF water IRON passing, notwithstanding the bad
condition OF the facings.
We are frequently obliged to carry canal
over stream OF water, and Cfce versa. In such
cases aqueducts are built. 1t is here parucu-
larly, as in aqueductS in general, that concrete
is Indispensable. II it be Thought proper to
build the arches of stones or bricks it is indis-
penSable, In order to resist filtration, to make
all the masonry above the arches of concrete.
In countries where proper materials tor max
ing the arches cannot be obtained at a reason
able rate it will be advantageous to make the
arches OF concrete, in which case the aqueduct
wilfbe formed of q single piece. Arches of large
dimensions may be constructed in this way
either for aQueductS or for ordinary bridges"
Capt. HOxie said that the concrete required by
the contract for the aqueduct extension mas
much greater strength than that used by Gen.
Vha nf xy.lta aH his
work continually and were allowed TO cover
each days work"
He quoted Gen. Gilmore on Clements and
MOrtars' Il SS3), the most recent and the pres
ent standard.work, as follows: Natural n.y.
draulic cement, to which, under circumstances
req uiring only a moderate degree OF energyand
strength, pdste OF fat lime is sometimes added,
in quantities seldom greatly exceeding that OF
the cement, is almost invariably used as the
basis OF the concrete mortar, and the concrete
when made is at once deposited in its allotted
place and we'll rammed in horizontal layers of
coarser fragments are driven below the general
surface. Concrete is admirably adapted
to variety of most important purposes and is
daily growing into more extensive use and ap-
plication. For foundations in damp and yield
ing soils, for subterranean and submarine
masonry, under almost every combination of
circumstances likely to occur in practice, it is
superior to 6richtCork in strength, DURABILITY and
economy, and In some exceptional cases is con-
sidered a reliable substitute for the best stone,
while 1t is almost always preferable to the
poorer varieties. For submarine masonry,
be laid without exhausting the water (Which
under the most favorable circumstances is an
expensive operation), and also without the aid
OF a diving bell or submarine armOr. On account
OF its continuity and impermeability to water,
1t is well suited to the purposes of a substratum
in soils Injected with springs for sewers and
conduits, for basement and sustaining walls,
for columns, piers and abutment t. Tor the heart
ing and backing of walls faced with bricks,
rubble and ashlar work, for pavements in
areas, Easements and cellars: for the walls and
floors of cisterns, vaults etc. Groined and
vaulted arches, and even entire bridges, dwell
ing houses and factories, in single monoIithic
masses, with moulded ornamentaiion of no
mean character, have been constructed OF this
Capt. Hoxie next quoted from Tanning on
"Water Supply Engineering" as follows: "Con-
wall is deep and very irregular it is well to level
up in the cuts with a tUater1proof concrete well
settled i'm place. and this may prove more eco
nOmical than TO cut the deep trench OF sufficient
width to receive reliable puddle wall; Also
the greater reliability Of the concrete under
great pressure should not be overlooked.
The foundation OF the chamber is to
be watertight, and capable of resisting success
fully the upward pressure upon the bottom
due to the head of water in the reservoir, when
the chamberis empty. The use of beUon
or hydraulic concrete is often advisable for the
bed-course of a valve chamber foundation to
aid in distributing the weight of the structure
and in securing q water-Lght floor. The COM
position OF the concrete is to be proportioned
for these especial objects. Concrete for a revet-
ment demands weight as q special element; for
Intel, tensile strength; for an arch compress
of a gate-chamber, inaperUiOusness which will
ensure sufficient strength. II there Is
the least transverse motion in a mortared wall
sustaining water, the masonry ceases from that
instant to be water-tight, and IL the>stones are
in the least disturbed on their bed after their
mortar has begun to set, the wall will never be
tight The foundations of masonry
conduits must be positively rigid, since the
is are TIC lneastS and
Capt. Hoxie also quoted Gen. Gillmore's de-
ScriptiOn OF q section of the Vanne aQueduct
supplying water to Paris, thirty-seven miles
half to three miles Of arches, eleven miles OF
tunnels, and bridges over rivers, canals and
highways of rs TO 1875 feet span. He cited the
foregoing authorities, with Col. Casey's report
court on ..Harb0urs and Docks, Clarke on the
"BostOn Maindrainage," and Chanute on ere
pairs Of Masonry" to show that wherever ex-
traordinary strength, endurance. imperme-
ability, permanence, or ready adaptability to
the greatest magnitude and Importance con-
crete Is used In preference to any other kind OF
masonry-and, often, where every other kind
would fail.
He also quoted Drinker on ssTunnelinp. Ex.
plosive Compounds and Rock Drills" to Show
that dry stone packing, ''howevcr well il is put
up, Will always yield somewhat to pressure"
and that without extraordinarily close super
fntendence 1t Is impossible to secure well exc
cuted dry back-fliing;" also from flaming on
"Water Supply Engineering" $50 long as the
foundation yields, the conduit cannot be main
tanned water ght. for the settling away OF the
verse strain upon the shell, and the adhesion of
the mortar 20 the masonry f. overcomo and the
work cracks" showing that the brick she'll
tunnel, would be ruptured throughout lis whole
length OF 10,So3 feet under the heavy preseuro
TO which It will be subjected, permitting the
water 70 escape into the assured rock.