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Rails should be ' keyed-up' so tightly as to ensure security, still 1 Keyingleaving a large amount of surplus strength in the chair to resist any the shock to which they may be exposed:-with wedges of varying dimensions, the chairs, which are frequently of unequal quality, and carelessly cast, are liable to be brought nearly to the breaking point, and to give way as soon as they are subjected to any additional strain. This has been avoided in the chairs and wedges under consideration, by giving them exact uniformity of dimensions. so formed as to drive equally well with either side to the rail, and compressed into five-sixths of their bulk, by the same process as is used for the treenails. Many advantages will result from this form of chair and wedge, Advanwith the treenails for fastening; the time occupied in laying the tagesoft'le rails is diminished; the holes for the fastenings may be bored ~~~ Chair and

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