126 RAILWAY CONSTRUCTION. 



diverted to one side, and a small artificial island made to receive 

 the curb above water-level. When a curb is fairly fixed in 

 position, the work of building the brick well can be commenced. 

 With the wrought-iron curb the triangular cavity between the 

 vertical plate and sloping plate must be filled with concrete to 

 form a level base for the first course of brickwork. The wooden 

 curb being composed of horizontal layers of timber, is ready to 

 receive the brickwork without further preparation. To strengthen 

 and keep the brickwork firmly tied together, strong wrought- 

 iron vertical tie-rods, \\ or 1 inch in diameter, are generally 

 built into the work as shown in the sketches at distances 

 about four feet apart. The lower end of the bottom tier of tie- 

 rods is secured to the curb, and the upper end passed through a 

 strong wrought-iron plate-ring, which is continuous all round 

 the brickwork. A long deep nut is screwed down over the top 

 or screwed end of tie-rod until the plate-ring is down tight on 

 the brickwork. The tightening nuts are made sufficiently deep 

 to receive the lower ends of a second series of vertical tie- 

 rods, which in like manner pass through another wrought-iron 

 plate-ring on the next section of brick well, and the same 

 arrangement is continued for the full height of the well. The 

 lengths of the tie-rods will depend upon the lengths of the 

 section of brickwork to be built at a time, and may vary from 

 10 to 15 feet. 



As the work of building proceeds the curb and brick well 

 will sink gradually into the ground, and down to a certain 

 depth, varying according to the material of the river bed, the 

 weight of the brick well itself will effect the penetration and 

 lowering. Beyond this depth the lowering must be done by 

 scooping or dredging the material from the inside of the well, 

 and placing heavy weights of old railway iron or other con- 

 venient masses on the top. When one section or length of well 

 has been sunk down, then another set of tie-rods are inserted 

 into the deep nuts, and another section of brickwork commenced. 

 The operation of lowering is rather tedious, as all the weights 

 have to be hoisted up on to the top of the length in hand, and 

 piled so as to leave space for lifting out the material dredged 

 from the interior ; and then, when the length has been lowered, 

 all the weights must be removed before the brickwork can be 

 resumed on another length. Where the river bed consists of 

 soft material, the excavation inside the well can generally be 



