On the Mole a very large seaplane base was established with the original passenger station as its principal building. Several other buildings for housing seaplanes, fuel, or bombs, and workshops were erected by the Germans close by. A merchant steamer, the _Brussels_, formerly commanded by the ill-fated Captain Fryatt, whom the Germans did to death so abominably, was moored alongside the station, and was believed to be used as living quarters for the personnel of the seaplane base. The broad portion of the Mole was used as a base for submarines passing through Zeebrugge _en route_ for Bruges or to the open sea; it was also used for such torpedo craft and mine-sweepers as were required for immediate duty in that locality. From the north-eastern large shed to the lighthouse the Mole had been turned into a veritable fortress. It was believed that the lighthouse was used as the Mole signal station. A battery of six or seven guns was situated on {30} the lighthouse extension of the Mole. These guns were at first surmised to be 3.5-inch guns, but it is probable that they were larger--in fact, up to 5.9-inch guns firing a shell of approximately one hundred pounds in weight. It was believed that the guns of this battery could fire out to sea and could be turned to fire towards the shore. Any vessel approaching from seaward and passing into the dredged channel, _en route_ to the canal, would be within the danger zone of this battery, from the latter's extreme range out at sea to the canal lock, always provided that the state of the visibility allowed the vessel to be seen. Incidentally, owing to the situation of the deep channel, the vessel would be obliged to pass within _a few yards_ of this battery when rounding the Mole end. A vessel endeavouring to berth alongside the outer wall would have to approach close to this battery, i.e., on a westerly course. At first sight it might appear feasible to approach _from_ the westward on an easterly course and thus avoid passing close to the battery, but that is not so. High tide and slack stream do not coincide on this coast. For about three hours on each side of high tide the streams run _to_ the eastward: at other states of the tide there would be insufficient depths of water for a vessel to berth alongside. It would therefore be necessary to approach from the eastward, i.e., to stem the tidal stream. [Illustration: AERIAL PHOTOGRAPH OF THE CANAL ENTRANCE. Taken shortly before the enterprise, showing the sandbanks narrowing the entrance channel. At the top of the photograph a dredger at work indicates the position of the approach channel]