It has been already stated that coast defence, and not service at sea, constitutes the especial sphere proposed for the Royal Naval Artillery Volunteers. The term coast defence is perhaps, in a certain sense, a misnomer. The defence of the most important of our commercial harbours against an attack from the sea could not be effectually conducted by a force composed exclusively of men trained for the land service alone. The approach to all the great ports of the United Kingdom from the sea involves the navigation of extensive estuaries, where floating batteries, and armed rafts, and the use of torpedoes, are essential to a complete defence, and would in point of fact effectually prevent the nearer approach of a hostile fleet. In the laying out of torpedoes on an extensive scale, a flotilla of boats would be required; and in furnishing crews for such boats, the well-trained oarsmen, who, it is hoped, will be found willing to enroll themselves in the Royal Naval Artillery Volunteers, would be enabled to render valuable service. In all probability, by their co-operation in the hour of danger, they would release an equal number of highly trained seamen, who would form the crews of sea-going cruisers. All our greatest ports, London, Hull, Newcastle, Leith and Granton, ports for Edinburgh, Glasgow, Bristol, Southampton, Belfast, Dublin, Cork, are situated at the head of an extensive estuary, or at some distance from the mouth of a navigable river. The mere enumeration of these names is sufficient to show how large a sphere there might be, in the event of a threatened invasion, for the employment, in the important and essential task of harbour defence, of an auxiliary force composed, not of trained seamen, but of persons who may be described generally as aquatics. It is to be observed that a mere oarsman, although not trained at the great guns, or in the use of rifle and cutlass, would be enabled to do good work in a service in which the use of boats must be largely resorted to; and that, in order to take a number at a gun mounted on a raft, such as the 'Nancy Dawson,' which the late Captain Cole improvised for our naval operations in the Sea of Azof, or to serve in a gun's crew in a floating battery for harbour defence, neither sea legs nor sea experience are indispensable qualifications. For such duties those qualities are required which equally combine to make a good gunner and a good soldier, whether afloat or on shore--a fair share of physical strength and activity, intelligence, and, above all, courage and patriotism. [Sidenote: The force need not be numerous.]