Chapter XIII: Act 1737: , and the Apportionment Act 1834, and is now allowed generally (4)

The built aqueduct may be either in tunnel, or cut-and-cover, the latter term denoting the process of cutting the trench, building the floor, side-walls, and roof, and covering with earth, the surface of the ground being restored as before. For works conveying water for domestic supply, the aqueduct is in these days, in England, always covered. Where, as is usually the case, the water is derived from a tract of mountainous country, the tunnel work is sometimes very heavy. In the case of the Thirlmere aqueduct, out of the first 13 m. the length of the tunnelled portions is 8 m., the longest tunnel being 3 m. in length. Conditions of time, and the character of the rock, usually require the use of machinery for driving, at any rate in the case of the longer tunnels. For the comparatively small tunnels required for aqueducts, two percussion drilling machines are usually mounted on a carriage, the motive power being derived from compressed air sent up the tunnel in pipes. The holes when driven are charged with explosives and fired. In the Thirlmere tunnels, driven through very hard Lower Silurian strata, the progress was about 13 yds. a week at each face, work being carried on continuously day and night for six days a week. Where the character of the country through which the aqueduct passes is much the same as that from which the supply is derived, the tunnels need not be lined with concrete, &c., more than is absolutely necessary for retaining the water and supporting weak places in the rock; the floor, however, is nearly always so treated. The lining, whether in tunnel or cut-and-cover, may be either of concrete, or brickwork, or of concrete faced with brickwork. To ensure the impermeability of work constructed with these materials is in practice somewhat difficult, and no matter how much care is taken by those supervising the workmen, and even by the workmen themselves, it is impossible to guarantee entire freedom from trouble in this respect. With a wall only about 15 in. thick, any neglect is certain to make the work permeable; frequently the labourers do not distribute the broken stone and fine material of the concrete uniformly, and no matter how excellent the design, the quality of materials, &c., a leak is sure to occur at such places (unless, indeed, the pressure of the outside water is superior and an inflow occurs). A further cause of trouble lies in the water which flows from the strata on to the concrete, and washes away some of the cement upon which the work depends for its watertightness, before it has time to set. For this reason it is advisable to put in the floor before, and not after, the sidewalls and arch have been built, otherwise the only outlet for the water in the strata is through the ground on which the floor has to be laid. Each length of about 20 ft. should be completely constructed before the next is begun, the water then having an easy exit at the leading end. Manholes, by which the aqueduct can be entered, are usually placed in the roof at convenient intervals; thus, in the case of the Thirlmere aqueduct, they occur at every quarter of a mile.

Timber aqueducts.

In some parts of America aqueducts are frequently constructed of wood, being then termed flumes. These are probably more extensively used in California than in any other part of the world, for conveying large quantities of water which is required for hydraulic mining, for irrigation, for the supply of towns and for transporting timber. The flumes are frequently carried along precipitous mountain slopes, and across valleys, supported on trestles. In Fresno county, California, there is a flume 52 m. in length for transporting timber from the Sierra Nevada Mountains to the plain below; it has a rectangular V-shaped section, 3 ft. 7 in. wide at the top, and 21 in. deep vertically. The boards which form the sides are 1-1/4 in. thick, and some of the trestlework is 130 ft. high. The steepest grade occurs where there is a fall of 730 ft. in a length of 3000 ft. About 9,000,000 ft. of timber were used in the construction. At San Diego there is a flume 35 m. long for irrigation and domestic supply, the capacity being 50 ft. per second; it has 315 trestle bridges (the longest of which is that across Los Coches Creek, 1794 ft. in length and 65 ft. in height) and 8 tunnels, and the cost was $900,000. The great bench flume of the Highline canal, Colorado, is 2640 ft. in length, 28 ft. wide, and 7 ft. deep; the gradient is 5.28 ft. per mile, and the discharge 1184 ft. per second.

Aqueduct in iron piping.

As previously stated, the type of aqueduct built of concrete, &c., can only be adopted where the ground is sufficiently elevated to carry it, and where the quantity of water to be conveyed makes it more economical than piping. Where the falling contour is interrupted by valleys too wide for a masonry structure above the surface of the ground, the detached portions of the built aqueduct must be connected by rows of pipes laid beneath, and following the main undulations of, the surface. In such cases the built aqueduct terminates in a chamber of sufficient size to enclose the mouths of the several pipes, which, thus charged, carry the water under the valley up to a corresponding chamber on the farther hillside from which the built aqueduct again carries on the supply. These connecting pipes are sometimes called siphons, although they have nothing whatever to do with the principle of a siphon, the water simply flowing into the pipe at one end and out at the other under the influence of gravity, and the pressure of the atmosphere being no element in the case. The pipes are almost always made of cast-iron, except in such cases as the lower part of some siphons, where the pressure is very great, or where they are for use abroad, when considerations of weight are of importance, and when they are made of rolled steel with riveted or welded seams. It is frequently necessary to lay them in deep cuttings, in which case cast-iron is much better adapted for sustaining a heavy weight of earth than the thinner steel, though the latter is more adapted to resist internal pressure. Mr D. Clarke (_Trans. Am. Soc. C.E._ vol. xxxviii. p. 93) gives some particulars of a riveted steel pipe 24 m. long, 33 to 42 in. diameter, varying in thickness from 0.22 in. to 0.375 in. After a length of 9 m. had been laid, and the trench refilled, it was found that the crown of the pipe had been flattened by an amount varying from 1/2 in. to 4 in. Steel pipes suffer more from corrosion than those made of cast-iron, and as the metal attacked is much thinner the strength is more seriously reduced. These considerations have prevented any general change from cast-iron to steel.

Mr. Clemens Herschel has made some interesting remarks (_Proc. Inst.
C.E._ vol. cxv. p. 162) as to the circumstances in which steel pipes
have been found preferable to cast-iron. He says that it had been
demonstrated by practice that cast-iron cannot compete with
wrought-iron or steel pipes in the states west of the Rocky Mountains,
on the Pacific slope. This is due to the absence of coal and iron ore
in these states, and to the weight of the imported cast-iron pipes
compared with steel pipes of equal capacity and strength. The works of
the East Jersey Water Company for the supply of Newark, N.J., include
a riveted steel conduit 48 in. in diameter and 21 m. long. This
conduit is designed to resist only the pressure due to the hydraulic
gradient, in contradistinction to that which would be due to the
hydrostatic head, this arrangement saving 40% in the weight and cost
of the pipes. For the supply of Rochester, N.Y., there is a riveted
steel conduit 36 in. in diameter and 20 m. long; and for Allegheny
City, Pennsylvania, there is a steel conduit 5 ft. in diameter and
nearly 10 m. long. The works for bringing the water from La Vigne and
Verneuil to Paris include a steel main 5 ft. in diameter between St.
Cloud and Paris.

Cast-iron pipes rarely exceed 48 in. in diameter, and even this
diameter is only practicable where the pressure of the water is low.
In the Thirlmere aqueduct the greatest pressure is nearly 180 lb. on
the square inch, the pipes where this occurs being 40 in. in diameter
and 1-3/4 in. thick. These large pipes, which are usually made in
lengths of 12 ft., are generally cast with a socket at one end for
receiving the spigot end of the next pipe, the annular space being run
with lead, which is prevented from flowing into the interior of the
pipe by a spring ring subsequently removed; the surface of the lead is
then caulked all round the outside of the pipe. A wrought-iron ring is
sometimes shrunk on the outer rim of the socket, previously turned to
receive it, in order to strengthen it against the wedging action of
the caulking tool. Sometimes the pipes are cast as plain tubes and
joined with double collars, which are run with lead as in the last
case. The reason for adopting the latter type is that the stresses set
up in the thicker metal of the socket by unequal cooling are thereby
avoided, a very usual place for pipes to crack under pressure being at
the back of the socket. The method of turning and boring a portion,
slightly tapered, of spigot and socket so as to ensure a watertight
junction by close annular metallic contact, is not suitable for large
pipes, though very convenient for smaller diameters in even ground.
Spherical joints are sometimes used where a line of main has to be
laid under a large river or estuary, and where, therefore, the pipes
must be jointed before being lowered into the previously dredged
trench. This was the case at the Willamette river, Portland, Oregon,
where a length of 2000 ft. was required. The pipes are of cast-iron 28
in. in diameter, 1-1/2 in. thick, and 17 ft. long. The spigots were
turned to a spherical surface of 20 in. radius outside, the inside of
the sockets being of a radius 3/8 in. greater. After the insertion of
the spigot into the socket, a ring, 3 in. deep, turned inside to
correspond with the socket, was bolted to the latter, the annular
space then being run with lead. These pipes were laid on an inclined
cradle, one end of which rested on the bed of the river and the other
on a barge where the jointing was done; as the pipes were jointed the
barge was carefully advanced, thus trailing the pipes into the trench
(_Trans. Am. Soc. C.E._ vol. xxxiii. p. 257). As may be conjectured
from the pressure which they have to stand, very great care has to be
taken in the manufacture and handling of cast-iron pipes of large
diameter, a care which must be unfailing from the time of casting
until they are jointed in their final position in the ground. They are
cast vertically, socket downwards, so that the densest metal may be at
the weakest part, and it is advisable to allow an extra head of metal
of about 12 in., which is subsequently cut off in a lathe. An
inspector representing the purchaser watches every detail of the
manufacture, and if, after being measured in every part and weighed,
they are found satisfactory they are proved with internal fluid
pressure, oil being preferable to water for this purpose. While under
pressure, they are rapped from end to end with a hand hammer of about
5 lb. in weight, in order to discover defects. The wrought-iron rings
are then, if required, shrunk on to the sockets, and the pipes, after
being made hot in a stove, are dipped vertically in a composition of
pitch and oil, in order to preserve them from corrosion. All these
operations are performed under cover. A record should be kept of the
history of the pipe from the time it is cast to the time it is laid
and jointed in the ground, giving the date, number, diameter, length,
thickness, and proof pressure, with the name of the pipe-jointer whose
work closes the record. Such a history sometimes enables the cause
(which is often very obscure) of a burst in a pipe to be ascertained,
the position of every pipe being recorded.

Cast-iron pipes, even when dipped in the composition referred to,
suffer considerably from corrosion caused by the water, especially
soft water, flowing through them. One pipe may be found in as good a
condition as when made, while the next may be covered with nodules of
rust. The effect of the rust is twofold; it reduces the area of the
pipe, and also, in consequence of the resistance offered by the rough
surface, retards the velocity of the water. These two results,
expecially the latter, may seriously diminish the capability of
discharge, and they should always be allowed for in deciding the
diameter. Automatic scrapers are sometimes used with good results, but
it is better to be independent of them as long as possible. In one
case the discharge of pipes, 40 in. in diameter, was found after a
period of about twelve years to have diminished at the rate of about
1% per year; in another case, where the water was soft and where the
pipes were 40 in. in diameter, the discharge was diminished by 7% in
ten years. An account of the state of two cast-iron mains supplying
Boston with water is given in the _Trans. Am. Soc. C.E._ vol. xxxv. p.
241. These pipes, which were laid in 1877, are 48 in. in diameter and
1800 ft. long. When they were examined in 1894-1895, it was estimated
that the tubercles of rust covered nearly one-third of the interior
surfaces, the bottom of the pipe being more encrusted than the sides
and top. They had central points of attachment to the iron, at which
no doubt the coating was defective, and from them the tubercles spread
over the surface of the surrounding coating. In this case they were
removed by hand, and the coating of the pipes was not injured in the
process. Cast-iron pipes must not be laid in contact with cinders from
a blast furnace with which roads are sometimes made, because these
corrode the metal. Mr Russell Aitken (_Proc. Inst. C.E._ vol. cxv. p.
93) found in India that cast-iron pipes buried in the soil rapidly
corroded, owing to the presence of nitric acid secreted by bacteria
which attacked the iron. The large cast-iron pipes conveying the water
from the Tansa reservoir to Bombay are laid above the surface of the
ground. Cast-iron pipes of these large diameters have not been in
existence sufficiently long to enable their life to be predicted. A
main, 40 in. in diameter, conveying soft water, after being in
existence fifty years at Manchester, was apparently as good as ever.
In 1867 Mr J.B. Francis found that no apparent deterioration had taken
place in a cast-iron main, 8 in. diameter, which was laid in the year
1828, a period of thirty-nine years (_Trans. Soc. Am. C.E._ vol. i. p.
26). These two instances are probably not exceptional.

Methods of laying.

Pipes in England are usually laid with not less than 2 ft. 6 in. of cover, in order that the water may not be frozen in a severe winter. Where they are laid in deep cutting they should be partly surrounded with concrete, so that they may not be fractured by the weight of earth above them. Angles are turned by means of special bend pipes, the curves being made of as large a radius as convenient. In the case of the Thirlmere aqueduct, double socketed castings about 12 in. long (exclusive of the sockets) were used, the sockets being inclined to each other at the required angle. They were made to various angles, and for any particular curve several would be used connected by straight pipes 3 ft. long. As special castings are nearly double the price of the regular pipes, the cost was much diminished by making them as short as possible, while a curve, made up of the slight angles used, offered practically no more impediment to the flow of water in consequence of its polygonal form, than would be the case had special bend pipes been used. In all cases of curves on a line of pipes under internal fluid pressure, there exists a resultant force tending to displace the pipes. When the curve is in a horizontal plane and the pipes are buried in the ground, the side of the pipe trench offers sufficient resistance to this force. Where, however, the pipes are above ground, or when the curve is in a vertical plane, it is necessary to anchor them in position. In the case of the Tansa aqueduct to Bombay, there is a curve of 500 ft. radius near Bassein Creek. At this point the hydrostatic head is about 250 ft., and the engineer, Mr Clerke, mentions that a tendency to an outward movement of the line of pipes was observed. At the siphon under Kurla Creek the curves on the approaches as originally laid down were sharp, the hydrostatic head being there about 210 ft.; here the outward movement was so marked that it was considered advisable to realign the approaches with easier curves (_Proc. Inst. C.E._ vol. cxv. p. 34). In the case of the Thirlmere aqueduct the greatest hydrostatic pressure, 410 ft., occurs at the bridge over the river Lune, where the pipes are 40 in. in diameter, and in descending from the bridge make reverse angles of 31-1/2 deg. The displacing force at each of these angles amounts to 54 tons, and as the design includes five lines of pipes, it is obvious that the anchoring arrangements must be very efficient. The steel straps used for anchoring these and all other bends were curved to fit as closely as possible the castings to be anchored. Naturally the metal was not in perfect contact, but when the pipes were charged the disappearance of all the slight inequalities showed that the straps were fulfilling their intended purpose. At every summit on a line of pipes one or more valves must be placed in order to allow the escape of air, and they must also be provided on long level stretches, and at changes of gradient where the depth of the point of change below the hydraulic gradient is less than that at both sides, causing what may be called a virtual summit. It is better to have too many than too few, as accumulations of air may cause an enormous diminution in the quantity of water delivered. In all depressions discharge valves should be placed for emptying the pipes when desired, and for letting off the sediment which accumulates at such points. Automatic valves are frequently placed at suitable distances for cutting off the supply in case of a burst. At the inlet mouth of the pipe they may depend for their action on the sudden lowering of the water (due to a burst in the pipe) in the chamber from which they draw their supply, causing a float to sink and set the closing arrangement in motion. Those on the line of main are started by the increased velocity in the water, caused by the burst on the pipe at a lower level. The water, when thus accelerated, is able to move a disk hung in the pipe at the end of a lever and weighted so as to resist the normal velocity; this lever releases a catch, and a door is then gradually revolved by weights until it entirely closes the pipe. Reflux valves on the ascending leg of a siphon prevent water from flowing back in case of a burst below them; they have doors hung on hinges, opening only in the normal direction of flow. Due allowance must be made, in the amount of head allotted to a pipe, for any head which may be absorbed by such mechanical arrangements as those described where they offer opposition to the flow of the water. These large mains require most careful and gradual filling with water, and constant attention must be given to the air-valves to see that the gutta-percha balls do not wedge themselves in the openings. A large mass of water, having a considerable velocity, may cause a great many bursts by water-ramming, due to the admission of the water at too great a speed. In places where iron is absent and timber plentiful, as in some parts of America, pipes, even of large diameter and in the most important cases, are sometimes made of wooden staves hooped with iron. A description of two of these will be found below.

Thirlmere.

The _Thirlmere Aqueduct_ is capable of conveying 50,000,000 gallons a
day from Thirlmere, in the English lake district, to Manchester. The
total length of 96 m. is made up of 14 m. of tunnels, 37 m. of
cut-and-cover, and 45 m. of cast-iron pipes, five rows of the latter
being required. The tunnels where lined, and the cut-and-cover, are
formed of concrete, and are 7 ft. in height and width, the usual
thickness of the concrete being 15 in. The inclination is 20 in. per
mile. The floor is flat from side to side, and the side-walls are 5
ft. high to the springing of the arch, which has a rise of 2 ft. The
water from the lake is received in a circular well 65 ft. deep and 40
ft. in diameter, at the bottom of which there is a ring of wire-gauze
strainers. Wherever the concrete aqueduct is intersected by valleys,
cast-iron pipes are laid; in the first instance only two of the five
rows 40 in. in diameter were laid, the city not requiring its supply
to be augmented by more than 20,000,000 gallons a day, but in 1907 it
was decided to lay a third line. All the elaborate arrangements
described above for stopping the water in case of a burst have been
employed, and have perfectly fulfilled their duties in the few cases
in which they have been called into action. The water is received in a
service reservoir at Prestwich, near Manchester, from which it is
supplied to the city. The supply from this source was begun in 1894.
The total cost of the complete scheme may be taken at about
L5,000,000, of which rather under L3,000,000 had been spent up to the
date of the opening, at which time only one line of pipes had been
laid.

Vyrnwy.

The _Vyrnwy Aqueduct_ was sanctioned by parliament in 1880 for the
supply of Liverpool from North Wales, the quantity of water obtainable
being at least 40,000,000 gallons a day. A tower built in the
artificial lake from which the supply is derived, contains the inlet
and arrangements for straining the water. The aqueduct is 68 m. in
length, and for nearly the whole distance will consist of three lines
of cast-iron pipes, two of which, varying in diameter from 42 in. to
39 in., are now in use. As the total fall between Vyrnwy and the
termination at Prescot reservoirs is about 550 ft., arrangements had
to be made to ensure that no part of the aqueduct be subjected to a
greater pressure than is required for the actual discharge. Balancing
reservoirs have therefore been constructed at five points on the line,
advantage being taken of high ground where available, so that the
total pressure is broken up into sections. At one of these points,
where the ground level is 110 ft. below the hydraulic gradient, a
circular tower is built, making a most imposing architectural feature
in the landscape. At the crossing of the river Weaver, 100 ft. wide
and 15 ft. deep, the three pipes, here made of steel, were connected
together laterally, floated into position, and sunk into a dredged
trench prepared to receive them. Under the river Mersey the pipes are
carried in a tunnel, from which, during construction, the water was
excluded by compressed air.

Denver.

_Denver Aqueduct._--The supply to Denver City, initiated by the
Citizens Water Company in 1889, is derived from the Platte river,
rising in the Rocky Mountains. The first aqueduct constructed is
rather over 20 m. in length, of which a length of 16-1/2 m. is made of
wooden stave pipe, 30 in. in diameter. The maximum pressure is that
due to 185 ft. of water; the average cost of the wooden pipe was
$1.36-1/2 per foot, and the capability of discharge 8,400,000 gallons
a day. Within a year of the completion of the first conduit, it became
evident that another of still greater capacity was required. This was
completed in April 1893; it is 34 in. in diameter and will deliver
16,000,000 gallons a day. By increasing the head upon the first pipe,
the combined discharge is 30,000,000 gallons a day. An incident in
obtaining a temporary supply, without waiting for the completion of
the second pipe, was the construction of two wooden pipes, 13 in. in
diameter, crossing a stream with a span of 104 ft., and having no
support other than that derived from their arched form. One end of the
arch is 24-1/2 ft. above the other end, and, when filled with water,
the deflection with eight men on it was only 7/8 of an inch. A
somewhat similar arch, 60 ft. span, occurs on the 34-in. pipe where it
crosses a canal. Schuyler points out (_Trans. Am. Soc. C.E._ vol.
xxxi. p. 148) that the fact that the entire water supply of a city of
150,000 inhabitants is conveyed in wooden mains, is so radical a
departure from all precedents, that it is deserving of more than a
passing notice. He says that it is manifestly and unreservedly
successful, and has achieved an enormous saving in cost. The sum saved
by the use of wooden, in preference to cast-iron pipes, is estimated
at $1,100,000. It is perhaps necessary to state that the pipe is
buried in the ground in the same way as metal pipes. The edges of the
staves are dressed to the radius with a minute tongue 1/16 in. high on
one edge of each stave, but with no corresponding groove in the next
stave; its object is to ensure a close joint when the bands are
tightened up. Leaks seldom or never occur along the longitudinal
seams, but the end shrinkage caused troublesome joint leaks. The
shrinkage in California redwood, which had seasoned 60 to 90 days
before milling, was frequently as much as 3 in. in the 20 staves that
formed the 34-in. pipe, and the space so formed had to be filled by a
special closing stave. Metallic tongues, 3/4 in. deep, are inserted at
the ends of abutting staves, in a straight saw cut. The bands, which
are of mild steel, have a head at one end and a nut and washer at the
other; the ends are brought together on a wrought-iron shoe, against
which the nut and washer set. The staves forming the lower half of the
pipe are placed on an outside, and the top staves on an inside, mould.
While the bands are being adjusted the pipe is rounded out to bring
the staves out full, and the staves are carefully driven home on to
the abutting staves. The spacing of the bands depends on
circumstances, but is about 150 bands per 100 ft. With low heads the
limit of spacing was fixed at 17 in. The outer surface of the pipe,
when charged, shows moisture oozing slightly over the entire surface.
This condition Schuyler considers an ideal one for perfect
preservation, and the staves were kept as thin as possible to ensure
its occurrence. Samples taken from pipes in use from three to nine
years are quite sound, and it is concluded that the wood will last as
long as cast-iron if the pipe is kept constantly charged. The bands
are the only perishable portion, and their life is taken at from
fifteen to twenty years. Other portions of the second conduit for a
length of nearly 3 m. were formed of concrete piping, 38 in. diameter,
formed on a mould in the trench, the thickness being 2-1/2 to 3 in. So
successful an instance of the use of wooden piping on a large scale is
sure to lead to a large development of this type of aqueduct in
districts where timber is plentiful and iron absent.

Pioneer, Utah.

_Pioneer Aqueduct, Utah._--The construction of the Pioneer Aqueduct,
Utah, was begun in 1896 by the Pioneer Electric Power Company, near
the city of Ogden, 35 m. north of Salt Lake City. The storage
reservoir, from which it draws its water, will coyer an area of 2000
acres, and contain about 15,000 million gallons of water. The aqueduct
is a pipe 6 ft. in diameter, and of a total length of 6 m.; for a
distance of rather more than 5 m. it is formed of wooden staves, the
remainder, where the head exceeds 117 ft., being of steel. It is laid
in a trench and covered to a depth of 3 ft. The greatest pressure on
the steel pipe is 200 lb. per sq. in., and the thickness varies from
3/8 to 11/16 in. The pipe was constructed according to the usual
practice of marine boiler-work for high pressures, and each section,
about 9 ft. long, was dipped in asphalt for an hour. These sections
were supported on timber blocking, placed from 5 to 9 ft. apart, and
consisting of three to six pieces of 6 X 6 in. timbers laid one on the
top of the other; they were then riveted together in the ordinary way.
The wooden stave-pipe is of the type successfully used in the Western
States for many years, but its diameter is believed to be unequalled
for any but short lengths. There were thirty-two staves in the circle,
2 in. in thickness, and about 20 ft. long, hooped with round steel
rods 5/8 in. in diameter, each hoop being in two pieces. The pipe is
supported at intervals of 8 ft. by sills 6 X 8 in. and 8 ft. long. The
flow through it is 250 cubic ft. per second.

Santa Ana.

The _Santa Ana Canal_ was constructed for irrigation purposes in
California, and is designed to carry 240 cub. ft. of water per second
(_Trans. Am. Soc. C.E._ vol. xxxiii. p. 99). The cross section of the
flumes shows an elliptical bottom and straight sides consisting of
wooden staves held together by iron and steel ribs. The width and
depth are each 5 ft. 6 in., the intended depth of water being 5 ft.
The staves are held by T-iron supports resting on wooden sills spaced
8 ft. apart, and are compressed together by a framework. They were
caulked with oakum, on the top of which, to a third of the total
depth, hot asphalt was run. The use of nails was altogether avoided
except in parts of the framework, it being noticed that decay usually
starts at nail-holes. It was found possible to make the flume
absolutely watertight, and in case of repair being necessary at any
part the framework is easily taken to pieces so that new staves can be
inserted. The water in the flume has a velocity of 9.6 ft. per second.
The Warm Springs, Deep, and Morton canons on the line are crossed by
wooden stave pipes 52 in. in diameter, bound with round steel rods,
and laid above the surface of the ground. The work is planned for two
rows of pipes, each capable of carrying 123 cub. ft. per second; of
these one so far has been laid. The lengths of the pipes at each of
the three canons are 551, 964 and 756 ft. respectively, and the
maximum head at any place is 160 ft. The pipes are not painted, and it
has been suggested that they would suffer in their exposed position in
case of a bush fire, a contingency to which, of course, flumes are
also liable.

New York.

_Aqueducts of New York._--There are three aqueducts in New York--the
Old Croton Aqueduct (1837-1843), the Bronx River Conduit (1880-1885),
and the New Croton Aqueduct (1884-1893), discharging respectively 95,
28, and 302 million U.S. gallons a day; their combined delivery is
therefore 425 million gallons a day. The Old Croton Aqueduct is about
41 m. in length, and was constructed as a masonry conduit, except at
the Harlem and Manhattan valleys, where two lines of 36-in. pipe were
used. The inclination of the former is at the rate of about 13 in. per
mile. The area of the cross-section is 53.34 sq. ft., the height is
8-1/2 ft., and the greatest width 7 ft. 5 in.; the roof is
semicircular, the floor segmental, and the sides have a batter on the
face of 1/2 in. per foot. The sides and invert are of concrete, faced
with 4 in. of brickwork, the roof being entirely of brickwork. There
is a bridge over the Harlem river 1450 ft. in length, consisting of
fifteen semicircular arches; its soffit is 100 ft. above high water,
and its cost was $963,427. The construction of the New Croton Aqueduct
was begun in 1885, and the works were sufficiently advanced by the
15th of July 1890 to allow the supply to be begun. The lengths of the
various parts of the aqueduct are as follows:--

Miles.
Tunnel 29.75
Cut-and-cover 1.12
Cast-iron pipes, 48 in. diameter, 8 rows. 2.38
-----
Croton Inlet to Central Park. 33.25
=====

The length of tunnel under pressure (circular form) is 7.17 m., and
that not under pressure (horse-shoe form) 23.70 m. The maximum
pressure in the former is 55 lb. per sq. in. The width and height of
the horse-shoe form are each 13 ft. 7 in., and the diameter of the
circular form (with the exception of two short lengths) is 12 ft. 3
in. The reason for constructing the aqueduct in tunnel for so long a
distance was the enhanced value of the low-lying ground near the old
aqueduct. The tunnel deviates from a straight line only for the
purpose of intersecting a few transverse valleys at which it could be
emptied. For 25 m. the gradient is 0.7 foot per mile; the tunnel is
then depressed below the hydraulic gradient, the maximum depth being
at the Harlem river, where it is 300 ft. below high water. The depth
of the tunnel varies from 50 to 500 ft. from the surface of the
ground. Forty-two shafts were sunk to facilitate driving, and in four
cases where the surface of the ground is below the hydraulic gradient
these are closed by watertight covers. The whole of the tunnel is
lined with brickwork from 1 to 2 ft. in thickness, the voids behind
the lining being filled with rubble-in-mortar. The entry to the old
and new aqueducts is controlled by a gatehouse of elaborate and
massive design, and the pipes which take up the supply at the end of
the tunnel are also commanded by a gate-house. The aqueduct, where it
passes under the Harlem river, is worthy of special notice. As it
approaches the river it has a considerable fall, and eventually ends
in a vertical shaft 12 ft. 3 in. in diameter (where the water has a
fall of 174 ft.), from the bottom of which, at a depth of 300 ft.
below high-water level, the tunnel under the river starts. The latter
is circular in form, the diameter being 10 ft. 6 in., and the length
is 1300 ft.; it terminates at the bottom of another vertical shaft
also 12 ft. 3 in. in diameter. The depth of this shaft, measured from
the floor of the lower tunnel to that of the upper tunnel leading away
from it, is 321 ft.; it is continued up to the surface of the ground,
though closed by double watertight covers a little above the level of
the upper tunnel. Adjoining this shaft is another shaft of equal
diameter, by means of which the water can be pumped out, and there is
also a communication with the river above high-water level, so that
the higher parts can be emptied by gravitation. The cost of the Old
Croton Aqueduct was $11,500,000; that of the new aqueduct is not far
short of $20,000,000.

Nadrai.

The _Nadrai Aqueduct Bridge_, in India, opened at the end of 1889, is
the largest structure of its kind in existence. It was built to carry
the water of the Lower Ganges canal over the Kali Naddi, in connexion
with the irrigation canals of the north-west provinces. In the year
1888-1889 this canal had 564 m. of main line, with 2050 m. of minor
distributaries, and irrigated 519,022 acres of crops. The new bridge
replaces one of much smaller size (five spans of 35 ft.), which was
completely destroyed by a high flood in July 1885. It gives the river
a waterway of 21,000 sq. ft., and the canal a waterway of 1040 sq.
ft., the latter representing a discharge of 4100 cub. ft. per second.
Its length is 1310 ft., and it is carried on fifteen arches having a
span of 60 ft. The width between the faces of the arches is 149 ft.
The foundations below the river-bed have a depth of 52 ft., and the
total height of the structure is 88 ft. It cost 44-1/2 lakhs of
rupees, and occupied four years in building. The foundations consist
of 268 circular brick cylinders, and the fifteen spans are arranged in
three groups, divided by abutment piers; the latter are founded on a
double row of 12-ft. cylinders, and the intermediate piers on a single
row of 20-ft. cylinders, all the cylinders being hearted with
hydraulic lime concrete filled in with skips. This aqueduct-bridge has
a very fine appearance, owing to its massive proportions and design.
(E. P. H.*)

AUTHORITIES.--For ancient aqueducts in general: Curt Merckel, _Die
Ingenieurtechnik im Alterthum_ (Berlin, 1899); ch. vi. contains a very
full account from the earliest Assyrian aqueducts onwards, with
illustrations, measurements and an excellent bibliography. For Greek
aqueducts see E. Curtius, "Uber stadtische Wasserbauten der Hellenen,"
in _Archaeologische Zeitung_ (1847); G. Weber (as above); papers in
_Athen. Mittheil._ (Samos), 1877, (Enneacrunus) 1892, 1893, 1894,
1905, and articles on ATHENS, PERGAMUM, &c. For Roman aqueducts: R.
Lanciani, "I Commentari di Frontino intorno le acque e gli
acquedotti," in _Memorie dei Lincei_, serie iii. vol. iv. (Rome,
1880), 215 sqq., and separately; C. Herschel, _The Two Books on the
Water Supply of the City of Rome of Sextus Julius Frontinus_ (Boston,
1899); T. Ashby in _Classical Review_ (1902), 336, and articles in
_The Builder_; cf. also the maps to T. Ashby's "Classical Topography
of the Roman Campagna," in _Papers of the British School at Rome_, i.,
in., iv. (in progress).

For modern aqueducts, see Rickman's _Life of Telford_ (1838);
Schramke's _New York Croton Aqueduct; Second Annual Report of the
Department of Public Works of the City of New York in 1872; Report of
the Aqueduct Commissioners_ (1887-1895), and _The Water Supply of the
City of New York_ (1896), by Wegmann; _Memoires sur les eaux de
Paris_, presentes par le Prefet de la Seine au Conseil Municipal (1854
and 1858); _Recherches statistiques sur les sources du bassin de la
Seine_, par M. Belgrand, Ingenieur en chef des ponts et chaussees
(1854); "Descriptions of Mechanical Arrangements of the Manchester
Waterworks," by John Frederic Bateman, F.R.S., Engineer-in-chief, from
the _Minutes of Proceedings of the Institution of Mechanical
Engineers_ (1866); _The Glasgow Waterworks_, by James M. Gale, Member
Inst. C.E. (1863 and 1864); _The Report of the Royal Commission on
Water Supply, and the Minutes of Evidence_ (1867 and 1868). For
accounts of other aqueducts, see the Transactions of the Societies of
Engineers in the different countries, and the Engineering Journals.

FOOTNOTES:

[1] There have been found at Caerwent, in Monmouthshire, clear traces
of wooden pipes (internal diameter about 2 in.) which must have
carried drinking-water, and almost certainly a pressure supply from
the surrounding hills. Some patches of lead also have been found
obviously nailed on to the pipes at points where they had burst (see
_Archaeologia_, 1908).

[2] This distance will not agree with the length given on some of the
_cippi_ (Lanciani, _Bull. Com._, 1899, 38).

[3] The course of the Aqua Claudia was considerably shortened by the
cutting of a tunnel 3 m. long under the Monte Affliano in the time of
Domitian (T. Ashby, in _Papers of the British School at Rome_, iii,
133).

[4] About 3 m. south-east of this point the presence of large
quantities of deposit and a sudden fall in the level of the channels
seems to indicate the existence of settling tanks, of which no actual
traces can be seen.

AQUILA [Greek: Akulas], (1) a Jew from Rome, who with his wife Prisca or Priscilla had settled in Corinth, where Paul stayed with them (Acts xviii. 2,3). They became Christians and fellow-workers with Paul, to whom they seem to have shown their devotion in some special way (Rom. xvi. 3, 4). (2) A native of Pontus, celebrated for a very literal and accurate translation of the Old Testament into Greek. Epiphanius (_De Pond. et Mens._ c. 15) preserves a tradition that he was a kinsman of the emperor Hadrian, who employed him in rebuilding Jerusalem (Aelia Capitolina, q.v.), and that he was converted to Christianity, but, on being reproved for practising pagan astrology, apostatized to Judaism. He is said also to have been a disciple of Rabbi 'Aqiba (d. A.D. 132), and seems to be referred to in Jewish writings as [Hebrew: akiles]. Aquila's version is said to have been used in place of the Septuagint in the synagogues. The Christians generally disliked it, alleging without due grounds that it rendered the Messianic passages incorrectly, but Jerome and Origen speak in its praise. Origen incorporated it in his _Hexapla_.

It was thought that this was the only copy extant, but in 1897
fragments of two codices were brought to the Cambridge University
Library. These have been published--the fragments containing 1 Kings
xx. 7-17; 2 Kings xxiii. 12-27 by F.C. Burkitt in 1897, those
containing parts of Psalms xc.-ciii. by C. Taylor in 1899. See F.C.
Burkitt's article in the _Jewish Encyclopaedia_.

AQUILA, CASPAR [KASPAR ADLER] (1488-1560), German reformer, was born at Augsburg on the 7th of August 1488, educated there and at Ulm (1502), in Italy (he met Erasmus in Rome), at Bern (1508), Leipzig (1510) and Wittenberg (1513). According to his son, he entered the ministry in August 1514, at Bern. He was for some time a military chaplain. In 1516 he became pastor of Jenga, near Augsburg. Openly proclaiming his adhesion to Luther's doctrine, he was imprisoned for half a year (1520 or 1522) at Dillingen, by order of the bishop of Augsburg; a death sentence was commuted to banishment through the influence of Isabella, wife of Christian II. of Denmark and sister of Charles V. Returning to Wittenberg he met Luther, acted as tutor to the sons of Franz von Sickingen at Ebernburg, taught Hebrew at Wittenberg, and aided Luther in his version of the Old Testament. The dates and particulars of his career are uncertain till 1527, when he became pastor at Saalfeld, and in 1528, superintendent. His vehement opposition to the Augsburg Interim (1548) led him to take temporary shelter at Rudolstadt with Catherine, countess of Schwarzburg. In 1550 he was appointed dean of the Collegiatstift in Schmalkalden. Here he had a controversy with Andreas Osiander. Restored to Saalfeld, not without opposition, in 1552, he remained there, still engaged in controversy, till his death on the 12th of November 1560. He was twice married, and left four sons. He published numerous sermons, a few Old Testament expositions and some controversial tracts.

See G. Kawerau, in A. Hauck's _Realencyklopadie_ (1896); _Allgemeine
deutsche Biog._ (1875); Lives by J. Avenarius (1718); J.G. Hillinger
(1731); Chr. Schlegel (1737); Fr. Gensler (1816).

AQUILA, SERAFINO DELL' (1466-1500), Italian poet and improvisatore, was born in 1466 at the town of Aquila, from which he took his name, and died in the year 1500. He spent several years at the courts of Cardinal Sforza and Ferdinand, duke of Calabria; but his principal patrons were the Borgias at Rome, from whom he received many favours. Aquila seems to have aimed at an imitation of Dante and Petrarch; and his poems, which were extravagantly praised during the author's lifetime, are occasionally of considerable merit. His reputation was in great measure due to his remarkable skill as an improvisatore and musician. His works were printed at Venice in 1502, and there have been several subsequent editions.

AQUILA, a city of the Abruzzi, Italy, the capital of the province of Aquila, and the seat of an archbishop, 2360 ft. above sea-level, 50 m. directly N.E. of Rome, and 145 m. by rail. Pop. (1901) town, 18,494; commune, 21,261. It lies on a hill in the wide valley of the Aterno, surrounded by mountains on all sides, the Gran Sasso d'Italia being conspicuous on the north-east. It is a favourite summer resort of the Italians, but is cold and windy in winter. In the highest part of the town is the massive citadel, erected by the Spanish viceroy Don Pedro de Toledo in 1534. The church of S. Bernardino di Siena (1472) has a fine Renaissance facade by Nicolo Filotesio (commonly called Cola dell' Amatrice), and contains the monumental tomb of the saint, decorated with beautiful sculptures, and executed by Silvestro Ariscola in 1480. The church of S. Maria di Collemaggio, just outside the town, has a very fine Romanesque facade of simple design (1270-1280) in red and white marble, with three finely decorated portals and a rose-window above each. The two side doors are also fine. The interior contains the mausoleum of Pope Celestine V. (d. 1296) erected in 1517. Many smaller churches in the town have similar facades (S. Giusta, S. Silvestro, &c.). The town also contains some fine palaces: the municipality has a museum, with a collection of Roman inscriptions and some illuminated service books. The Palazzi Dragonetti and Persichetti contain private collections of pictures. Outside the town is the _Fontana delle novantanove cannelle_, a fountain with ninety-nine jets distributed along three walls, constructed in 1272. Aquila has some trade in lace and saffron, and possesses other smaller industries. It was a university town in the middle ages, but most of its chairs have now been suppressed.

Aquila was founded by Conrad, son of the emperor Frederick II., about 1250, as a bulwark against the power of the papacy. It was destroyed by Manfred in 1259, but soon rebuilt by Charles I. of Anjou. Its walls were completed in 1316; and it maintained itself as an almost independent republic until it was subdued in 1521 by the Spaniards, who had become masters of the kingdom of Naples in 1503. It was twice sacked by the French in 1799.

See V. Bindi, _Monumenti storici ed artistici degli Abruzzi_ (Naples,
1889), pp. 771 seq.

AQUILA, in astronomy, the "Eagle," sometimes named the "Vulture," a constellation of the northern hemisphere, mentioned by Eudoxus (4th cent. B.C.) and Aratus (3rd cent. B.C.). Ptolemy catalogued nineteen stars jointly in this constellation and in the constellation _Antinous_, which was named in the reign of the emperor Hadrian (A.D. 117-138), but sometimes, and wrongly, attributed to Tycho Brahe, who catalogued twelve stars in Aquila and seven in Antinous; Hevelius determined twenty-three stars in the first, and nineteen in the second. The most brilliant star of this constellation, [alpha]-_Aquilae_ or Altair, has a parallax of 0.23", and consequently is about eight times as bright as the sun; [eta]-_Aquilae_ is a short-period variable, while _Nova Aquilae_ is a "temporary" or "new" star, discovered by Mrs Fleming of Harvard in 1899.

AQUILA ROMANUS, a Latin grammarian who flourished in the second half of the 3rd century A.D. He was the author of an extant treatise _De Figuris Sententiarum et Elocutionis_, written as an instalment of a complete rhetorical handbook for the use of a young and eager correspondent. While recommending Demosthenes and Cicero as models, he takes his own examples almost exclusively from Cicero. His treatise is really adapted from that by Alexander, son of Numenius, as is expressly stated by Julius Rufinianus, who brought out a supplementary treatise, augmented by material from other sources. Aquila's style is harsh and careless, and the Latin is inferior.

Halm, _Rhetores Latini minores_ (1863); Wensch, _De Aquila Romano_
(1861).

AQUILEIA, an ancient town of Italy, at the head of the Adriatic at the edge of the lagoons, about 6 m. from the sea, on the river Natiso (mod. Natisone), the course of which has changed somewhat since Roman times. It was founded by the Romans in 181 B.C. as a frontier fortress on the north-east, not far from the site where, two years before, Gaulish invaders had attempted to settle. The colony was led by two men of consular and one of praetorian rank, and 3000 _pedites_ formed the bulk of the settlers. It was probably connected by road with Bononia in 175 B.C.; and subsequently with Genua in 148 B.C. by the Via Postumia, which ran through Cremona, Bedriacum and Altinum, joining the first-mentioned road at Concordia, while the construction of the Via Popilia from Ariminum to Ad Portum near Altinum in 132 B.C. improved the communications still further. In 169 B.C., 1500 more families were settled there as a reinforcement to the garrison. The discovery of the goldfields near the modern Klagenfurt in 150 B.C. (Strabo iv. 208) brought it into notice, and it soon became a place of importance, not only owing to its strategic position, but as a centre of trade, especially in agricultural products. It also had, in later times at least, considerable brickfields. It was originally a Latin colony, but became a _municipium_ probably in 90 B.C. The customs boundary of Italy was close by in Cicero's day. It was plundered by the Iapydes under Augustus, but, in the period of peace which followed, was able to develop its resources. Augustus visited it during the Pannonian wars in 12-10 B.C. and it was the birthplace of Tiberius's son by Julia, in the latter year. It was the starting-point of several important roads leading to the north-eastern portion of the empire--the road (Via Iulia Augusta) by Iulium Carnicum to Veldidena (mod. Wilten, near Innsbruck), from which branched off the road into Noricum, leading by Virunum (Klagenfurt) to Lauricum (Lorch) on the Danube, the road into Pannonia, leading to Emona (Laibach)[1] and Sirmium (Mitrowitz), the road to Tarsatica (near Fiume) and Siscia (Sissek), and that to Tergeste (Trieste) and the Istrian coast.

In the war against the Marcomanni in A.D. 167, the town was hard pressed; the fortifications had fallen into disrepair during the long peace. In A.D. 238, when the town took the side of the senate against the emperor Maximinus, they were hastily restored, and proved of sufficient strength to resist for several months, until Maximinus himself was assassinated. The 4th century marks, however, the greatest importance of Aquileia; it became a naval station and, probably, the seat of the _corrector Venetiarum et Histriae_; a mint was established here, the coins of which are very numerous, and the bishop obtained the rank of patriarch. An imperial palace was constructed here, in which the emperors after the time of Diocletian frequently resided; and the city often played a part in the struggles between the rulers of the 4th century. At the end of the century, Ausonius enumerated it as the ninth among the great cities of the world, placing Rome, Mediolanum and Capua before it, and called it "moenibus et portu celeberrima." In A.D. 452, however, it was destroyed by Attila, though it continued to exist until the Lombard invasion of A.D. 568. After this the patriarchate was transferred to Grado. In 606 the diocese was divided into two parts, and the patriarchate of Aquileia, protected by the Lombards, was revived, that of Grado being protected by the exarch of Ravenna and later by the doges of Venice. In 1027 and 1044 Patriarch Poppo of Aquileia entered and sacked Grado, and, though the pope reconfirmed the patriarch of the latter in his dignities, the town never recovered, though it continued to be the seat of the patriarchate until its formal transference to Venice in 1450. The seat of the patriarchate of Aquileia had been transferred to Udine in 1238, but returned in 1420 when Venice annexed the territory of Udine. It was finally suppressed in 1751, and the sees of Udine and Gorizia (Gorz) established in its stead. Its buildings served as stone quarries for centuries, and no edifices of the Roman period remain above ground. Excavations have revealed one street and the north-west angle of the town walls, while the local museum contains over 2000 inscriptions, besides statues and other antiquities. The cathedral, a flat-roofed basilica, was erected by Patriarch Poppo in 1031 on the site of an earlier church, and rebuilt about 1379 in the Gothic style by Patriarch Marquad. The narthex and baptistery belong to an earlier period. Of the palace of the patriarchs only two isolated columns remain standing. The modern village (pop. 2300) is rendered unhealthy by rice-fields.