Leading from the canal entrance to the tip of the Mole, on which stood a third light-house, and so out to sea, was a curved channel, about three-quarters of a mile long, kept clear by continual dredging; and this was protected both by a string of armed barges and by a system of nets on its shoreward side. It was in its great sea-wall, however, some eighty yards broad and more than a mile long, that Zeebrugge's chief strength resided; and this had been utilized, since the German occupation, to the utmost extent. Upon the seaward end of it, near the light-house, a battery of 6-inch guns had been mounted, other batteries and machine-guns being stationed at various points throughout its length. With a parapet along its outer side, some sixteen feet higher than the level {225} of the rest of the Mole, it not only carried a railway-line but contained a seaplane shed, and shelters for stores and _personnel_. It was connected with the shore by a light wood and steel viaduct--a pile-work structure, allowing for the passage of the through-current necessary to prevent silting. Emplaced upon the shore, on either side of this, were further batteries of heavy guns; while, to the north of the canal entrance, and at a point almost opposite to the tip of the Mole, was the Goeben Fort containing yet other guns covering both the Mole and the harbour. Under the lee of the parapet were dug-outs for the defenders, while, under of the lee of the Mole itself was a similar shelter for the enemy's submarines and destroyers. Nor did this exhaust the harbour's defences, since it was further protected not only by minefields but by natural shoals, always difficult to navigate, and infinitely more so in the absence of beacons. Even to a greater extent was this last feature true of Ostend, though here the whole problem was somewhat simpler, there being no Mole, and therefore no necessity--though equally no opportunity--for a subsidiary attack. Covered, of course, from the shore by guns of all calibres--and here it should be remembered that there were 225 of these between Nieuport and the Dutch frontier--the single object in this case was to gain the entrance, before the block-ships should be discovered by the enemy, and sunk by his gunners where their presence would no do harm. Since for complete success, however, it was necessary to seal both places, and, if possible, to do so simultaneously, {226} it will readily be seen that, in the words of Sir Eric Geddes--the successor, as First Lord of the Admiralty, to Mr. Balfour and Sir Edward Carson--it was "a particularly intricate operation which had to be worked strictly to time-table." It was also one that, for several months before, required the most arduous and secret toil.