Müllerian 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ The upper ends of these numerous involutions unite together and form a string of cells, at first solid, but very soon acquiring a lumen, and becoming a duct which communicates (as it clearly must from its mode of formation) , at numerous points with the pleuro-peritoneal cavity. It is very probable that there is one involution to each segment of the body between the front and hind ends of the Oviduct. This duct is the Wolffian duct, which thus, together with the Oviduct, is formed before the appearance of the external gills. ”

“ 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. ”

“ The new conduit for water supply of Baltimore is a continuous tunnel, seven miles long, running from the dam to the receiving reservoir—“Lake Montebello.” In its construction no open cuts were made; all work being done by drifting. Its depth below the surface of ground varies from 65 to 360 feet. The internal diameter is 12 feet; the fall is one foot per mile; capacity 170 millions daily. Fifteen shafts were sunk during the constructive work. Two miles of the tunnel were through material that required to be arched with brick ”

“ There; an emergency pressure duct, designed to open automatically in the event of malfunction of the ship's atmospheric regulators. Emergency pressure could be built up through the ducts in the event of any sudden fall of more than eight ounces per square inch; and would be instantly released should it mount more than three pounds above. All he had to do was jam this single duct to the "excess" position and hold his breath.
It was like picking a lock with his bare fingers, and they felt like fat sausages. ”

“ 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 ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ Strange to say, he had not advanced more than a few hundred rods before I noticed that there was a strong current of air blowing through the tunnel in the direction Bulger had taken.
Every moment it increased in violence, fairly lifting us from our feet and bearing us along through this narrow bore made by nature’s own hands and lighted too by lamps of her own fashioning. The motion of the air through this vast pipe caused bursts of mighty tones as if peeled forth by some gigantic organ played by giant hands. ”

“ 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. ”

“ That the means of ventilating the tunnel could have been and be so readily disconnected from the boring machine (i.e., by the movement of a single lever that would pour a stream of compressed air coming from the supply pipe directly into the tunnel) that it has never been necessary that a single inch of cutting should have taken place in order to protect life or to secure ventilation, nor can such necessity arise in the future. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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 quantity of water capable of being taken from the Diveria in winter, when the rivers which are dependent upon the mountain snows for their supply are at their lowest, is calculated to be 352 gallons per second. Thus, taking the fall to be diminished by friction, etc., to 440 ft., and the useful effect at 70%, there is obtained 2000 H. P. on the turbine shaft.
The metallic conduit varies in material according to the pressure; thus cast-iron pipes 3 ft. in diameter and 13⁄16 in. thick are used up to a pressure of 2 atmospheres, from which point they are of wrought-iron. ”

“ 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. ”

“ From the fact that no attempt whatever is made to protect the conductors, one would naturally suppose that every time there is a rain the road would be compelled to shut down; for, as the slot through which the plow travels is open, water can enter the conduit with the greatest freedom, and, in trickling down the sides, would be caught to some extent upon the brackets c c, and thus make its way over to the channel bars a a, and thereby destroy the insulation. ”

“ When objectionable to have the work exposed in the rooms, taps may be made in the moulding opposite each room and the circuit extensions from the moulding to the center outlets in the rooms may be run in flexible conduit, fishing the wires from the moulding to the ceiling outlet. The use of wooden moulding in new buildings is not to be recommended for the reason that it is not usually fireproof, and it would be better to run the conductors concealed in some form of conduit ”