Early in the afternoon Pariset and Kenneth started, working towards Brussels by way of Tirlemont and Louvain. Kenneth had been provided with field-glasses, through which he closely scanned every bridge and culvert, while Pariset piloted the machine. Flying low, they were able to examine the line thoroughly. All that Kenneth had to guide him was the knowledge that the bridge was near a mill. There was a tunnel between them. It was therefore pretty clear that the bridge and the mill could not be far apart. They flew over the main line as far as Brussels without discovering any bridge that fulfilled the conditions. Then they retraced their course and scouted along the branch lines running south from Louvain, Tirlemont and Landen respectively. Within a few hours they had examined the whole triangular district that had Brussels, Liége, and Namur at its angles. At Namur they descended for a short rest, then set off again, to try their luck on the lines running from the French frontier. Both felt somewhat discouraged. To trace the many hundreds of miles of railway that crossed the country between the Meuse and the Somme promised to be work for a week. Indeed, it was getting dark by the time they had run through the coal-mining and manufacturing district between Mons and Valenciennes. Alighting at the latter place, they heard that great numbers of German troops had already crossed the Belgian frontier, and the forts of Liége were being attacked. There was much excitement in the town, and Pariset had some difficulty in getting petrol to replenish his tanks. Next morning they set off early along the line running eastward through Maubeuge to Charleroi. It seemed unlikely that they would find the spot they sought in the midst of a manufacturing district, but if they were to succeed, nothing must be left untried. Towards ten o’clock they were crossing a stream to the south-east of Charleroi when Kenneth suddenly gave a shout. He had noticed on the stream a water-mill, between which and a larger river, apparently the Sambre, the railway crossed the stream on a brick bridge of four arches. The mill was at least two hundred yards from the bridge, a distance that seemed too great to have been tunnelled; but it was the first spot he had seen that in any way conformed to the particulars he had overheard, and it appeared worth while to examine the place more closely. The importance of the bridge was obvious. Its destruction would seriously delay the transport of any French troops that might be sent northwards to support Namur or Liége, and correspondingly assist the Germans in an attempt to take either of those towns by a coup de main.