Silveira and his motley host, therefore, were doing admirable service to the cause of their country when they occupied 9,000 out of Soult’s 21,000 men from April 20 to May 2 on the banks of the Tamega. The ground was in their favour, but far stronger positions had been forced ere now, and it was fortunate that this one was maintained for so many days. The town of Amarante, it must be remembered, lies on comparatively low ground: its bridge is completely commanded by the heights on which Silveira had planted his camp and his batteries. The river flows in a deep-sunk ravine, and was at this moment swollen into an impassable torrent by the melting of the mountain snows. Loison more than once sent swimmers by night, in search of places where the strength of the current might be sufficiently moderate to allow of an attempt to pass on rafts or boats. Not one of these explorers could get near the further bank: they were swept off by the rushing water and cast ashore far down stream, on the same side from which they had started. There had been bridges above Amarante at Mondim and Aroza, and below it at Canavezes, but reconnaissances showed that they had all three been blown up, and that Portuguese detachments were watching their ruins, to prevent any attempt to reconstruct them. Loison found, therefore, that he could not turn Silveira’s position by a flanking movement: there was nothing to do save to wait till the river should fall, or to attempt to force the bridge of Amarante at all costs. Continual rains made it hopeless to expect the subsidence of the Tamega for many days, wherefore Loison devoted all his energies to the task of capturing the bridge. Even here there was one difficulty to be faced which might prove fatal: the French engineers had discovered that the structure was mined. It was necessary, therefore, not only to drive back the Portuguese, but to prevent them from blowing up the bridge at the moment of their retreat. Loison had entrusted the details of the attack on the bridge to Delaborde, whose infantry held the advanced posts. That officer first tried to approach the head of the bridge by means of a flying sap; but when it had advanced a certain distance the fire of the Portuguese from across the river became so deadly, that after many men had been killed in the endeavour to work up to the palisades on the bridge, the attempt had to be abandoned. The next device recommended by the engineers was that an attempt should be made to lay a trestle bridge at a spot some way below the town, where a mill-dam contracted the width of the angry river. This was found to be impossible, the stream proving to be far deeper than had been supposed, while the Portuguese from the left bank picked off many of the workmen [April 25].