Suppose for a moment that the entire Mole had been built in solid formation--i.e., that the tidal stream had no free passage under the viaduct. The west-going stream would tend to carry sand into the roadstead between the Mole and the canal entrance, whereas the east-going stream would be unable to remove the deposit a few hours later. Thus the roadstead would soon have become useless, and access to the canal would have been impracticable. The sand along the whole Flanders coast was extremely susceptible to movement. Such tendency was partially countered by the extensive use of groynes. These latter, however, could not be carried {25} very far out into the sea owing to the difficulties of construction and repair. There were, therefore, no artificial barriers to prevent the movement of the sand to the eastward or westward beyond a short distance from the shore. Hence the necessity for keeping a portion of the Mole open to allow the tidal stream to flow in both directions. Even so, a large shoal had formed in the roadstead, and reduced the acreage available for anchorage purposes. When first designed the open viaduct was of shorter length than that eventually constructed; the alteration was considered necessary after local experience of the silt had been obtained. The iron piles, or pillars, on which the viaduct was supported were of great strength and much interlaced with steel rods to allow for severe buffeting in heavy gales and to take the strain of railway traffic. A portion was actually demolished by a gale when under construction, and the completion of the Mole was consequently delayed for many months. When making enquiries in search of expert advice on questions of salvage, I had an interesting conversation with an individual who had had considerable experience in salving vessels in other waters. Maybe this book will remind him of our discussion. In his opinion salvage work presented no great difficulties. It was only a matter of obtaining the necessary apparatus, he thought, and any vessel--concrete-filled or otherwise--could be removed in a month or so. "How about silt?" I asked. "Oh, silt shouldn't make much difference," he replied, and added, "but we have no silt to speak of in that part of the world, so I cannot say for certain." {26} We then discussed the possibilities of salving a blockship at Zeebrugge, for he had been informed of the proposed operation. Eventually our conversation nearly resulted in a wager; that we came to no terms was perhaps due to the fact that payment might have necessitated application to a war widow. The first and second portions of the Mole had not been materially altered by the Germans during their occupation. [Sidenote: The Outer Wall and the Parapet]