While this movement was in progress, but before crossing the river, a reserve supply for seventeen days was accumulated at Springfield. It may be assumed therefore that this represents the conditions which Sir Redvers Buller thought requisite to his projected operation. The necessity of depending chiefly upon the slow-moving ox-wagons, and their comparatively small capacity, made the organising of the train tedious and difficult. "To forward supply alone," wrote Buller, "took 650 ox-wagons, and as between Frere and Springfield there are three places where all the wagons had to be double-spanned, and some required three spans, some idea of the difficulties may be formed." A correspondent with the army states that the wagons "can only be depended upon to haul not more than 600 pounds each." To lessen this great inconvenience road traction-engines were employed with success. The same writer says of these that "they can easily haul twelve tons, and on {p.235} a flat, dry veldt strip along at a brisk eight miles an hour. They leisurely descend into spruits--beds of streams--roll across, and wheel up stiff long climbs like flies walking up a wall. They are not quite helpless, even when the ground has been soaked by rain."[29] [Footnote 29: Burleigh, "Natal Campaign," p. 240.] While these preparations were making, the besieged had to resign themselves to further weary endurance. "Sir Redvers Buller," writes a correspondent within, "has sent a heliograph message bidding us wait in patience for another month until siege artillery can reach him." The bombardment was maintained by the Boers with increased but monotonous regularity, intensified from time to time as movements among Buller's troops led them to strengthen their forces upon the Tugela, with a consequent weakening of those of investment.