Wolffian duct

“ As the workmen became skillful, the progress was excellent.
All costs of labor in the tunnel chargeable to duct laying amounted to $0.039 per ft. of duct; top charges brought this up to $0.083.
The serious problem was to guard against grout and mortar running into the duct opening through the joints from the concrete, which was a rather wet mixture. Each joint was wrapped, when laid, with canvas, weighing 10 oz. per sq. yd., dipped in cement grout immediately before [Pg 478] using. These wraps were 6 in. wide, and were cut long enough to go around the lap about the middle of the duct. ”

“ 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. ”

“ That the method which be has invented 'for securing the proper feed under all circumstances' without 'objectionable features is to make the bore of the duct of comparatively large size and then restrict the duct by means of a wire or rod preferably centrally located therein to leave a channel of the proper size.'
'This arrangement is simple; but in a long experience it has been found to be entirely successful. It is possible to secure the correct drop-by-drop feed with a duct of considerable size, since the friction of the water on the large area of the tube-wall and wire reduces its flow. ”

“ If a fault suddenly develops on a circuit, the chances are it will be found in a manhole, and an inspection of the cable in the manhole will generally reveal the trouble without resorting to locating with a Wheatstone bridge. The cable is often cut through at the edge of the duct, or damaged by something falling on it, or by some one "walking all over it." ”

“ 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. ”

“ Elaborate arrangements have to be made for draining the conduit, as any accumulation of mud or water in contact with the conductors, or the special insulators supporting them, would be fatal to the working of the system. And in practice the ordinary drainage has to be assisted by continual scraping of the conduit with special brushes and by repeated flushing during the hours when the cars are not running. Heavy rains and snowstorms are therefore liable to upset the working of the system; and the tramway manager has to employ quite an army of men simply to keep the conduit in working order. ”

“ The art of making it has been lost. The conduits, always covered, were carried on arcades only where it was necessary to cross a valley or a plain above its level; for the rest of their way they ran in places upon the surface of the ground, but mostly below it. Thus of the 58 miles of the Anio Novus, 49 were underground. No two aqueducts were on the same level, and so, where their courses converged, it was both possible and convenient to carry one conduit upon another, because it was forbidden by law to erect a building within a certain number of feet on either side of an aqueduct ”

“ It is obvious, therefore, how greatly the design and construction of the aqueduct have grown in importance, and what care must be exercised in order that the supply upon which such large populations depend may not be interrupted, and that the country through which such large volumes of water are conveyed may not be flooded in consequence of the failure of any of the works.
Practically only two types of aqueduct are used in England. The one is built of concrete, brickwork, &c., the other of cast-iron (or, in special circumstances, steel) pipes. ”

“ 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 ”

“ So that Wellington boasts the possession of the largest wooden building and the highest wooden viaduct, as is alleged, which the world contains.
The viaduct is raised on sixteen concrete basements. It contains 212,000 superficial feet of kauri timber, and there are thirty-five tons of wrought iron used up in bolts, nuts, washers, and straps alone. At a distance it looks like a gigantic web, or the puzzle of a dreaming geometrician. It is 170 feet in height, above the stream, and the span over the valley is 185 feet. ”

“ Two or three short tunnels, or deep cuttings, across the Downs, are the only costly work to be done. By commencing at the sea end, all the material of the cuttings could be loaded on barges at once, carried out to sea, and then discharged; or shipped to ports where limestone is in demand. If I am not mistaken, one-half the capital required for the Channel Tunnel would suffice.
Besides communicating with Paris, such a canal would supply London with sea-water for baths and other purposes, thus covering all the conduit schemes that have from time to time been projected for this purpose. ”

“ Near to where the stream is further swollen by receiving the waters of the Ceiriog, it is spanned by the majestic aqueduct which carries the waters of the Ellesmere Canal, one of those few architectural achievements which, placed where Nature has done her utmost, add a new beauty to their surroundings. Even more unrestrained praise might be given to the fine, slender, lofty pillars and arches of the Dee viaduct, which is among the greatest works of the Great Western Railway. The aqueduct is Telford’s work, and the viaduct was built by Robertson. ”

“ The bridge over Georgetown Creek, on line of Washington Conduit, is 200 feet span with two cords of iron pipe 4 feet in diameter, 11⁄2 inches thickness, used as water conductors. The pipes were first lined with staves of resinous pine 3 inches thick to prevent freezing, but have been taken out. No allowance is made for expansion or contraction. A similar plan is in use at Philadelphia, over the valley of Wissahikon, consisting of two 20 inch cast-iron flange pipes serving as top members of a series of inverted bow-string trusses. There are four spans, each 169 feet 9 inches. ”

“ 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. ”

“ This is a practice on which we do not look with much complacency; it is the compromise between cost and security, to which the affairs of men are so often compelled. No doubt, a conduit from three to six inches in diameter is much less subject to a breach in its continuity than one which is smaller; but, when no collars are used, the pipes should be laid with extreme care, and the bed which is prepared for them at the bottom of the drain should be worked to their size and shape with great accuracy. ”

“ The ladder forms, the refuge-niche forms, and overhead conductor 137 pocket forms were attended to by one man, who set, removed, cleaned, and repaired them. The carpenters on the night shift set the arch centers and gantries, also the manhole forms when needed. The conduit layers on the night shift laid up half the 4-way conduits (3-high) and one-third of the single ducts (4-high) . This one gang laid the conduits in two sections of bench-wall each night, that is, one section at Weehawken and the other at the western end. ”

“ But, and this is the odd thing, at a3, about eight metres before the channel ends, a pipe issues from the stone channel and running parallel to the Pnyx rock conducts the water to the main reservoir (Haupt-Bassin) . A similar arrangement has been observed in the aqueduct at Samos. There, too, the conduit pipe leaves the rock channel before it ends. It is conjectured [272] that this was a plan intended to mislead an enemy who might desire to cut off the water-supply.
The conduit actually debouches at a5 into the great reservoir from which the new fountain-house Nine-Spouts must have been fed. ”

“ The weight of all structures was then transferred to the permanent steel viaduct, erected on the sides of the avenue, by timber bents under the transverse girders resting on the permanent steel viaduct, and all weight was thus taken off the central rock core. This core was then excavated to sub-grade, the permanent viaduct was completed, and all structures were placed on its deck, using concrete piers and timber bents. ”

“ In one bench wall of each tunnel there were fifteen openings for power cables and in the other, between the river shafts, there were forty openings for telephone, telegraph, and signal cables. East of the Long Island shaft, the number of the latter was reduced to twenty-four. The telephone ducts were all of the four-way type. The specifications required that the power ducts should have an opening of not less than 3-1/2 in., nor more than 3-7/8 in., and that after laying they should pass a 4-ft. mandrel, 3-3/8 in. ”

“ West Shore to 1153 feet, the East Shore shaft to 1185 feet, and the boring of the tunnel toward the center of the river has made good progress, the easterly section having advanced at the present writing about 260 feet, and the westerly section 170 feet from their respective shafts. Both the shafts and the tunnel will be lined with a high grade of Portland cement concrete which will give them a finished internal diameter of 14 feet. The aqueduct reaches the Hudson River at an elevation of 400 feet above mean water level. ”

“ Repairs to the channel itself should not be made in the summer time, in order not to stop the flow of water at a time when the demand for it is the greatest, but should be made in the spring or autumn, and with the greatest speed possible, and of course with all preparations made in advance, in order that the conduits may be out of commission as few days as possible. As is obvious to every one, a single aqueduct must be taken at a time, for if several were cut off at once, the supply would prove inadequate for the City's needs. ”

“ The vast masses of earth piled on this alluvial base to the height of 135 feet will certainly settle, and as the drift material of this base or foundation has varying depth, to 250 feet or more, the settlement of the new mass, as well as its base, will be unequal, and it is predicted that cracks and fissures in the dam will be formed, which will be reached and used by the water under the pressure above mentioned, and will cause the destruction of the dam and the draining off of the great lake upon which the integrity of the entire canal rests. ”

“ The plans which were before spoken of for a bridge of masonry across this valley, contemplated a structure which would maintain the regular inclination of the Aqueduct; and the channel-way would have been formed of masonry having a cast iron lining; but a more full consideration of the subject suggested the propriety of using iron pipes over the bridge, even if it had been carried up to the grade plane of the Aqueduct: when the use of iron pipes was determined upon, then considerations of economy induced them to build the work only high enough to comply with the requirements of the law. ”

“ Both Wilson and Wolverton knew the country below Green River, Utah, having made surveys through much of the surrounding territory. Wolverton said we must surely see his father, who lived down the river and who was an enthusiast on motor boats. A few minutes' work the next morning sufficed to get our boats over the dam. The dam was constructed of loose rock and piles, chinked with brush and covered with sloping planks,—just a small dam to raise the water for irrigation purposes. Much of the water ran through the canal; in places the planks were dry, in others some water ran over. ”

“ All that would be necessary would be to allow the tube to terminate in a tolerably large open space; and from a point in the base vertically above this, to let fall a plumb-line through a fine vertical boring into this open space. It would thus be found how far the point from which the plumb-line was let fall lay, either to the east or to the west of the optical axis of the underground tunnel, and therefore how far to the east or to the west of the centre of the open mouth of this tunnel. ”

“ By this method of reasoning a nation which can build a battleship of 16,000 tons displacement is impotent if it can not build one of twice that tonnage, and if this reason applies to quantity of material, why not say that a nation which can dig a canal 150 feet wide through a mountain some seven miles in length admits its impotence if it can not dig one 300 feet wide, or 600 feet, if it should please to do so? But why should it be less difficult or a declaration of impotency on the part of our engineers to build a safe lock canal including a satisfactory and safe controlling dam at Gatun? ”