In the early days the engineers in their bridge-building operations suffered the maximum width of a river to dictate what the length of such a structure should be. Seeing that the normal channels of many of these waterways are narrow in comparison with what they attain under flood, this rendered bridge-work exceedingly expensive and intricate. It is no uncommon circumstance for a waterway, when swollen by the rains of the wet season, to spread out for a width of three miles or more. It becomes practically insatiable, the soft earth forming the banks falling a ready victim to the powerful eroding action of the scurrying water. The result is worse than that brought about by the scouring of the River Mississippi, which devours huge masses of land continually on either bank. When the Indian river falls, unsightly stretches of undulating sandbanks are revealed, riven by little back channels and small lagoons, which present a general aspect of desolation. Under such circumstances, bridging from bank to bank is a somewhat vague undertaking, for the simple reason that it is difficult to decide what are the limits of the waterway, because erosion continues until the water reaches material which defies this action. The engineer has met this situation now in an ingenious manner. He determines the channel of the river and keeps it within bounds by means of an artificial wall or training-bund, which is carried parallel with the navigable channel, the flow of water through the space between the inner side of the wall and the shore being obstructed by a solid embankment which carries the track. This system was employed first by Mr. J. B. Bell to carry the North-Western State railway across the Chenab River at Sher Shah, and proved so eminently successful that it has come into general favour. [Illustration: THE TRAINING-BUND OR WALL TO NARROW THE GANGES BY 3000 FEET FOR THE CURZON BRIDGE, SHOWING RAILWAY APPROACH] One of the latest and most interesting, as well as largest undertakings of this class, is that in connection with the Curzon railway bridge over the Ganges at Allahabad, for the Allahabad-Fyzerbad railway. At this point the river flows between high banks of hard clay about 3 miles apart, and so resistant is this earth to scouring action that erosion has been brought to cessation practically. The width of the waterway, however, is about 1¼ miles, and when it was decided to span the river, a great length of steel appeared inevitable. [Illustration: ERECTING THE PIERS FOR THE CURZON BRIDGE The training-bund is to be seen in the background.]