Messrs. Gates & Green also make a patent socketless access-pipe, in connection with which a loose fire-clay ring or thimble is slipped over for the purpose of making the joint. The access-hole permits the workman to put in his hand and make good the joints. This is shown in Fig. 400, which sufficiently explain- itself.

Fig 400   Oates & Green 's Patent Socketless Access pipe:R,loose fire clay ring to make the socket.

Fig 400 - Oates & Green 's Patent Socketless Access-pipe:R,loose fire-clay ring to make the socket.

Socketed access-pipes with junctions are also made for insertion instead of the ordinary junction. In case of a stoppage in the branch-drain, by removing this access-cover an examination can be made, and if necessary cleaning tackle inserted. The diameter of the junction-piece being less than that of the main pipe from which it is branched, the invert is slightly higher, and owing to the inclination of the smaller drain, it may be necessary to set up the junctionpiece to conform to this gradient, and in order to prevent subsequent displacement when the trench is being refilled, means should be taken to provide a firm foundation underneath the branch. In order to prevent any chance of the omission of this very necessary work, some makers have lately introduced junctions with rest-pieces, which enable a firm base to be obtained simply, as will be seen on reference to Fig. 401.

Fig. 4001  Codling's Patent Reast  Bend Junction.

Fig. 4001- Codling's Patent Reast- Bend Junction.

Where the connection has to be made to a brick sewer, the brickwork must be cut out sufficiently to allow of the insertion of a properly-radiated highly-glazed fire-clay oblique junction-block, having square bed, sides, and top, as shown in Fig. 402, which must be set in cement mortar, and the brickwork made good thereto. In districts where the sewers are liable to be back-watered from tide-locking or the rise of Hoods, these junction-blocks should be fitted with a flap-valve, which will close with the pressure of the rising sewage in the main sewer, and so prevent the flooding of basements and the like. These valves have already been described

The first stage in the work of con struetion is of course the excavation of the trench to the required depth. The trench should not be made wider than necessary to allow sufficient room for the pipe-layer to work, [f it be over 10 feel deep it should be 3 feet wide, if the depth be less than that 2 feet 6 inches in width, and if it he no more than 4 or 5 feet deep, so that the earth can be thrown out without intermediate staging, a width of 2 feet 3 incites is sufficient. The surface-material should be carefully put on one side for reinstatement in its proper place, and the excavated material neatly and compactly deposited alongside the trench, so as to do as little damage and occasion as little inconvenience as possible; all surplus rubbish must be removed promptly as the works proceed. In cutting through gardens and grounds the necessity of these conditions will be appreciated, and at the same time particular care must be taken to do as little damage as possible to the foliage and roots of trees and shrubs. The length of trench to be opened out at one time will be governed by the number of men constantly kept at work, the nature of the ground, and the interference with the proper use of and access to the premises. When the trench is contiguous to walls and buildings, whose foundations may be liable to disturbance by reason of the trench being kept open an undue length of time, it should only be got out in short lengths, and the work rapidly completed and the trench refilled; this applies also in cases where the ground has been "made", the material being necessarily somewhat loose. If running sand be met with, the work should proceed cautiously in short lengths. Rock should be hewn out by hand, as Masting is too risky in the immediate neighhourhood of property; when tIntrench, however, is at a safe distance from houses, Masting may be resorted to, provided the contractor takes the sole responsibility for accidents of every kind. It it customary to open out trenches down to a depth of 16 feet This requires three lifts or stages for getting the material up to the surface. The additional expense beyond this depth of having an extra lift, makes it cheaper to resort to tunnelling; hut before this is done all the surrounding circumstances must be fully weighed and considered - that is to say, whether the ground immediately above the heading is sufficiently solid to admit of tunnelling, also whether due supervision can be exercised over the construction of the work, and whether the contractor can be relied upon to securely pack the heading so as to leave all thoroughly sound.

Fig. 402   Junctions For Brick Sewer: B and C, junction Blocks; D, invert block.

Fig. 402 - Junctions For Brick Sewer: B and C, junction Blocks; D, invert-block.

Where water occurs in the trench, proper provision must be made for its abstraction as the works proceed, by forming proper dams and sumps for the purpose, into which the suction-pipe of a pump must be inserted, care being taken to afterwards remove from the sump all wet and loose slurry, and to make

• 1 the hole with concrete up to the level of the pipe- In case any existing drains arc met with, following the same course as the trench and likely to interfere with the progress of the new work, they must l>e diverted into temporary wooden troughs, and carried past the work as it proceeds to a temporary outlet, so as to avoid as far as possible any damage that might be caused to the bottom of the trench by the escape of water. Proper care must also be taken to maintain any drains which may come across the trench, cast-iron pipes being substituted for the pipes removed, of such a length that they will get a firm and even bearing on either side of the trench.