It is not possible to give here the exact details of this highly ingenious device upon which so much scientific and practical attention was wisely bestowed, but sufficient has been said to enable the reader to form a clear conception of how the mine was caught and held away from the ship's side by the deflecting wire of the paravane.
This device, in one of its many forms, was fitted not only to warships, but also to many hundreds of merchantmen, and was known to have saved thousands of tons of valuable shipping and cargo.
Among those devices which had for their object the minimising of the result of a mine explosion may be mentioned the "Blister System" so successfully employed in the construction of monitors and other big ships, the idea being to surround the inner hull with an outer casing which received the effect of the explosion of either a mine or torpedo and left the inner or real hull of the ship water-tight. Its one weak feature was that it reduced the speed of the ship and the ease with which she could be man[oe]uvred. In future types of large and heavily armed ships this drawback will undoubtedly be largely overcome by an increase in engine-power made possible by the development of engineering science.
The "blister," although outwardly forming a continuous structure round the entire vessel, extending well above and below the water-line, tapered off towards the bows and stern, and was subdivided into different compartments. In this way an explosion against one section did not necessarily damage any other part. The British monitors which so successfully bombarded the Belgian coast and the fortifications of the Dardanelles were fitted with blisters, and more than one of them owed their salvation to this means.
CHAPTER XIII
THE MINE BARRAGE
What undoubtedly forms the most effective counter to unrestricted submarine warfare is the explosive mine barrage, as employed against the German U-boats in the North Sea and the Straits of Dover.
The practicability of these barrage systems depends, however, very largely upon the following factors:—(1) the geographical features of the area of operations; (2) the hydrographical peculiarities of the seas in which the mines have to be laid; (3) the number of properly equipped mine-laying vessels available; (4) an adequate and highly trained personnel; and (5) the mechanical skill and manufacturing power of the nation employing the system.