Volume Eleven - Pre-Victorian to the Present Day - some more aspects - The Steam Navvy and the Dock Extension of 1883 . . .

On the central road are kept the empty wagons, and on each side is a man with a horse, by whom an empty wagon is brought forwards along the jump to the side of the machine ; and as soon as it is filled it is run back along the branch and another empty, is brought up. Meanwhile the wagon on the other side is being filled ; and while this is in its turn being exchanged for an empty, a second wagon is being filled on the first side. As the work thus proceeds on either side alternately, not a moment need be lost in waiting for wagons ; and the jib has the minimum distance to swing round, the dirt from each half of its sweep delivered on its own side.

When, say, a dozen wagons have accumulated on each of the side roads, the shunting engine makes up a train, and takes them away to be tipped. The central siding behind the machine should be long enough for say 32 wagons at least; and other sidings are of course necessary if the “ lead ” to the tips be a long distance.

Figures 11, 12, 13, 14, & 15 - Dunbar and Ruston's Steam Navvy - Excavation Views.

The gullet thus made may be 20 ft. or even 30 ft. deep, according to the nature of the stuff ; but 25 ft. is about the most economical depth, because the machine has then sufficient reach to make the cutting exactly large enough for an ordinary double-line railway of standard gauge, the slopes requiring very little handwork to finish them, as shown by the section in Fig. 11.

In Fig. 12 is shown a cutting 50 ft. deep for a similar railway, which can be best made by driving two navvies, one in advance of the other, to take out the first 25 ft. ; and then finishing the lower half of the depth with a gullet similar to that shown in Fig. 11.

In each case the completed cutting is shown by the dark section, and the part to be taken out by hand by a light colour. In the deep cutting, Fig. 12, the sleepers and ballast of the permanent way are drawn in ; whilst in the other, Fig. 11, are shown the positions of the side roads while the work is in progress.