Duct

“ This duct and spur correspond, I believe, with the two ducts in Coronula; but besides these, a duct (a) is given off from one end of the gland, from the surface opposite to that at which the cement-trunk enters. This duct (a) is very singular, from always forming a loop (a′) , with two spurs projecting from it: these two spurs occasionally spring from a common point: I have seen nothing like this structure in any other Cirripede. This duct (a) runs, like the duct (c) , to the margin of its own disc of basal membrane, where it debouches. ”

“ Branch ducts should never be made to enter a main duct on the outer side of a bend, because at this point the pressure of the current of air inside the duct is increased. They should join up on the inside of a bend, where the pressure is reduced. ”

“ At such times as the pipe became uncoupled inside the duct line, the part remaining inside was recovered by the use of the tool shown at D, Fig. 15, called a “weasel.” In two instances, the mandrel became stuck in such a manner that the duct line had to be cut into in order to take it out.
The best day’s work of the rodding gang (1 foreman and 4 men) was 20,400 duct ft. of the 4-way conduit in the telegraph and telephone line, and 19,200 duct ft. of single conduit on the low-tension line, an average day’s work under ordinary conditions being about 10,000 duct ft. ”

“ In the section of the tunnel in which there were circumferential reinforcement rods in the duct bench, the rods were in place before the laying commenced, as they had been placed with the invert concrete. The circumferential reinforcing rods in the arch came down into the upper part of the duct bench concrete; these rods were put in position and tied to the iron lining in the crown at the same time as the duct bench concrete was being finished off. Openings for the manholes were left in the duct bench at the regular stationing.
The average time taken to fill a length of 35 ft. ”

“ By its very nature a duct is a structure which can hardly arise de novo. We must even suppose that the segmental organs of Annelids were themselves transformations of still simpler structures. On the other hand I would point to the development in this very duct amongst Amphibians and Osseous fishes of a glandular portion similar to that of a segmental tube, as an à posteriori proof of its being a metamorphosed segmental tube. ”

“ In the 657,000 duct ft. of conduit in the river tunnels only eight serious obstructions were met. That the work was of exceptionally high quality is shown by the fact that a heavy 3-in. lead cable has been passed through from manhole to manhole (450 ft.) in 6 min., and the company, engaged to lay the cables in these ducts, broke all its previous records for laying, not only for tunnel work, but also in the open.
Fig. 1, Plate XXXV, shows a collection of the tools and arrangements used in laying and rodding ducts. ”

“ The reader will have been struck with the similarity between this aqueduct and those of ancient Rome; it remains to be shown that there is one other point of resemblance, in the air-shafts that are built at intervals of a mile. They rise 14 feet above the ground, and, like the old Roman ones, are in the form of towers. Every third one is provided with a door and way of access into the conduit. But the conduit is without the filtering-places and the angles. ”

“ 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. ”

“ Aqueducts
paces broad, and five feet deep, [63] through one of which a volume of very good fresh water, the bulk of a man's body, flows into the heart of the city, from which all supply themselves, and drink. The other which is empty brings the water, when they wish to clean the first conduit, for, while one is being cleaned, the water flows through the other. Conduits as large round as an ox's body bring the fresh water across the bridges, thus avoiding the channels by which the salt-water flows, and in this manner the whole city is supplied, and everybody has water to drink. ”

“ An aqueduct or canal extends in a direct line from the palace towards the mountains, a distance of at least a mile. It is an exceedingly massive work, consisting of two walls raised perhaps fifteen feet above the level of the plain, and built of very large blocks of hewn stone. The intervening space is filled with earth. At present, a small conduit, a foot or so wide, brings all the water which is required for the use of the inhabitants of Iskardo ”

“ When the conduit is being laid, a wooden mandrel about four or five feet long, three inches in diameter, and carrying a leather or rubber 829 washer from three to eight inches larger at one end is drawn through each duct so as to draw out any particles of foreign matter or cement which may have become lodged in the joints, and also to insure good alignment of the tiles, as shown in fig. ”

“ The conducting of the water through lead pipes is to be managed as follows. If there is a regular fall from the source to the city, without any intervening hills that are high enough to interrupt it, but with depressions in it, then we must build substructures to bring it up to the level as in the case of channels and conduits. ”

“ By substituting inverted syphons instead of maintaining a uniform declivity in the conduit, would not give the requisite discharge of water at the elevation of the terminus of the Aqueduct, and perhaps they preferred, rather than diminish this elevation of the supply of water, to incur the expense of high structures across valleys. ”

“ The level of this branch pipe is about 120 feet below the bottom of the Aqueduct on the north side of the valley; affording an opportunity for a beautiful jet d’eau;—such an one as cannot be obtained at the fountains in the city. From an orifice of seven inches diameter the column of water rises to a height of 115 feet when there is only a depth of 2 feet of water in the Aqueduct. ”

“ This water was very abundant, but it appeared more like the continuous stream of an aqueduct than a natural spring of water; it was at a very low level, quite 30 ft. underground. At a considerably higher level, and near the surface of the ground, was an aperture into the brick specus or conduit of an aqueduct of the third century, in which the water was flowing steadily along from west to east; this continued all the summer of 1874, and the water was always flowing. This aperture was closed in the summer of 1875, and the whole specus buried again ”

“ The most magnificent and costly section of the aqueduct—and one which the now well-known principle in hydraulics, that water will rise to the level of its head, shows to have been useless both in labor and expense—is a lofty arcade, a conspicuous ornament of the city, by which the aqueduct is carried across a deep valley from the hill of Santa Theresa to that of San Antonio opposite. ”

“ Sometimes the main conduits are made of lime-mortar, as in the island of Jerbah. The field to be irrigated is divided into small squares or compartments, sometimes oblong of about seven by five feet in size; each is edged up with a small embankment of earth; between each line of squares run parallel ducts or gutters of earth, communicating with one large and common conduit, which is usually placed, to run better, on the highest part of the field, and as nearly as possible cutting it into halves. ”

“ Great stone water-pipes, with rim and hollow for fitting to the next pipes tightly, lie scattered in all directions, peeping up through the long grass and ferns, or hiding among the roots of the thorn trees. Elsewhere are to be seen longer stretches of aqueduct, whose architects have been able to turn strength into beauty in a very wonderful fashion. ”

“ Surface ducts 100 feet or more in thickness may extend from land out to sea when warm air from the land flows over the cooler ocean surface. Elevated ducts from a few feet to more than 1,000 feet in thickness may occur at elevations of 1,000 to 5,000 feet, due to the settling of a large air mass. ”

“ But many have not been content to confine themselves to their limits, but have laid hands on the aqueducts themselves by puncturing, here and there, the side walls of the channels, not merely those who have secured a right to draw water, but also those who misuse the occasion of the least favour for attacking the walls of the conduits. ”

“ Between the place where the water of an aqueduct is delivered and the spring, the ground may rise into hills and descend into valleys, and the pipes which convey the water may follow all the undulations84 of the country, and the water will run freely, provided no pipe is laid higher than the spring. ”

“ Water Tower and Roman Ruins, Chester, England
The constructive details of these old water courses are as interesting as are their general design. At the mouth of each aqueduct there generally was constructed a reservoir in which to collect water from the springs or streams that supplied it, and in which impurities could settle before the clarified water was delivered into the channel. The water channel was usually formed either of stone or brick coated on the inside with cement to make it water-tight. ”

“ In nearly all the species of the first five orders mentioned, the ducts grow in concentric rows, in the first of the season's growth; those which, form later may be inclined through the layer of wood-cells, becoming smaller as they approach the outer portion. In the live oak, the ducts run radially through the ring, and the small fibers are nearly solid, giving the wood great hardness, making it so valuable for ship-building. ”

“ The aqueduct, forming part of the extravagant scheme of irrigation of which the Machine de Marly and the great canal of Maintenon commemorate successive disastrous phases, frames, in its useless lofty openings, such charming glimpses of the country to the southwest of Versailles, that it takes its place among those abortive architectural experiments which seem, after all, to have been completely justified by time. ”

“ Tall piers may be found badly out of the upright due to sinking of foundations. A marked case of this kind came under the author’s notice—a viaduct of fifteen semicircular arches, in which, though many piers were wanting in truth, one in particular was about 1 foot 4 inches out of vertical, making one side of the shaft plumb, and doubling the normal batter of the other. ”

“ The height of this celebrated work from the bed of the river is nearly a hundred feet; yet, to–day it is overtopped by the Midland viaduct, from which, as we glide past, the dell is seen half as much again below. Aqueducts are common enough, and so are viaducts, but it is seldom that we have the opportunity of contemplating at the same moment a twofold series of arches of equal grandeur, the viaduct consisting of no fewer than thirteen. ”

“ For the conveyance of the current to any distance you must build either enclosed or open aqueduct; and in the hot square of the city where you set it free, you find it good for health and pleasantness to let it leap into a fountain. ”

“ Aqueduct.—The total length of the aqueduct, from the intake dam to the South Reservoir, is 18,700 m., made up as shown in Table 4.
TABLE 4.—Estanzuela Aqueduct.
The gradient of the concrete pipes is 0.43% from Estanzuela to Mederos, and 0.53% from Mederos to the South Reservoir. The calculated discharging capacity of the conduit when running full is 364 497liters (13 cu. ft.) per sec. for the upper, and 465 liters (16.4 cu. ft.) per sec. ”

“ The making of one tunnel so much resembles the making of another,—the building of bridges and viaducts, no matter how extensive, so much resembles the building of others,—the cutting out of “dirt,” the blasting of rocks, and the wheeling of excavation into embankments, is so much a matter of mere time and hard work,—that is quite unnecessary for us to detain the reader by any attempt at their description. ”

“ Its survey crosses no rivers; but were a canal to do so, it would, if on the same level, let the river run into the canal and act as a water-feeder. If not on a level, either the river or the canal would be crossed by an aqueduct. Mountains are tunnelled, or the route laid out around them. ”

“ Canal construction consists chiefly of open-cut excavation, but embankments, aqueducts, tunnels, culverts, bridges, and a variety of other construction work are involved. The plant used and methods adopted in excavating canals depend very largely upon the size of the canal section and the material encountered. In rock the practice is the same everywhere, and consists in the use of power drills and explosives for breaking up the rock, and derricks, conveyors, and cars hauled by animal or mechanical power for removing it. ”

“ This tunnel descends into the Reservoir, so that the centre of it at the mouth is about 12 feet below the surface91 of the water; any floating substance cannot enter it, and during the winter season when the water is frozen over no obstruction can take place to the flow into the Aqueduct, and during the summer season the water will be drawn from a level where it is cooler than at the surface. ”

“ When repairs have to be made stop-gates allow of the water being run off by “off-lets” from a short reach, and afterwards restored with but little interruption of the traffic. These off-lets are pipes placed at the level of the bottom of the canal and provided with valves which can be opened when required. They are generally formed at aqueducts or bridges crossing rivers, where the contents of the canal between the stop-gates can be run off into the stream. ”