Moreover, as native labour was to superintend the work of opening and closing the bridge, the simplest arrangement possible was essential, and, furthermore, had to be capable of hand manipulation. The designing engineers, Sir Douglas Fox & Partners, and Sir Charles Metcalfe, Bart., evolved an ingenious solution. On the top of two adjacent piers carrying the span in its normal position, a tower was erected on either side of the opening, with two simple, single, vertical racks on either tower. At the top of each tower a platform extending the width of the bridge was provided, together with a large sprocket wheel at either end. A chain passed over each sprocket wheel, one end being attached to a corner of the bridge, and the other to a heavy counterweight. To open the bridge, all that the natives have to do is to wind a winch which rotates the sprocket wheel, and as the counterweight descends the whole span rises vertically and horizontally, being guided in its movement by the rack on each tower. The counterweight is the full width of the bridge, and when the span has been lifted to its fullest extent the counterbalance weight lies across the track, to form a high barrier to any one attempting to cross the bridge when the span is open. It will be seen that the bridge acts on the principle of a sash window, where the sash weight counterbalances the weight of the moving portion, and in lifting only the friction of the moving parts has to be overcome. To guard against disaster from tampering or misuse, the bridge, when either raised or lowered, is locked. To lower the bridge it is only necessary to reverse the winding direction of the winch. The span of steel moved in this manner weighs 55 tons, and the whole operation of opening and closing occupies about half-an-hour, eight men under a native superintendent sufficing for the movement of the winches. It is an unusual type of lifting bridge, but it is doubtful whether a simpler and cheaper means of meeting the situation could have been devised, while the maintenance expenses--a vital consideration in such a remote country--are reduced to insignificance. About 12 miles out of Chiromo the railway commences a heavy climb, as it has to gain a summit level of 4000 feet to reach the plateau. The ascent is through very tumbled country. The ruling grade is 1 in 44, and the minimum curve is of 363 feet radius. As the valley winds amazingly, the line is a continuation of curves winding round crags and bluffs. Here and there the mountain sides are torn by wide clefts that have had to be spanned by bridges, which are supported on steel towers, carried on pedestals or plinths built of concrete. One of the largest bridges of this class is that across the M’Swadzi River, which is 290 feet long.