At the same time the whole faith of the German military staff so far as airship operations are concerned, is pinned to the Zeppelin. Notwithstanding its many drawbacks it is the vessel which will be used for the invasion of Great Britain. Even the harbour question, which is admitted to be somewhat acute, has been solved to a certain degree. At strategical points permanent harbours or airship sheds have been established. Seeing that the airships demand considerable skill in docking and undocking, and that it is impossible to achieve these operations against the wind, swinging sheds have been adopted. On water the practice is to anchor a floating harbour at one end, leaving the structure to swing round with the wind. But on dry land such a dock is impossible. Accordingly turntable sheds have been adopted. The shed is mounted upon a double turn-table, there being two circular tracks the one near the centre of the shed and the other towards its extremities. The shed is mounted upon a centre pivot and wheels engaged with these inner and outer tracks. In this manner the shed may be swung round to the most favourable point of the compass according to the wind. In the field, however, such practices are impossible, and the issue in this connection has been overcome by recourse to what may be termed portable harbours. They resemble the tents of peripatetic circuses and travelling exhibitions. There is a network of vertical steel members which may be set with facility and speed and which are stayed by means of wire guys. At the top of the outer vertical posts pulleys are provided whereby the outer skin or canvas forming the walls may be hauled into position, while at the apex of the roof further pulleys ensure the proper placing of the roofing. The airship is able to enter or leave from either end according to conditions. The material is fireproofed as a precautionary measure, but at the same time the modern aerial bomb is able to penetrate the roofing without any difficulty and to explode against the airship anchored within.