"A Staff Officer," writing in _The Times_ of July 16, 1860, declared that the most efficacious and the most economical line of defence which London could have would be a circular railway forming a complete cordon around the Metropolis at a distance of fifteen miles from the centre, and having for its interior lines of operation the numerous railways already existing within that radius. On this circular railway there should be "Armstrong and Whitworth ordnance mounted on large iron-plated trucks" fitted with traversing platforms in the way already recommended by W. Bridges Adams, the trucks themselves, however, and not only the locomotives, being protected by "shot-proof shields." The circular railway was to be constructed primarily for strategical purposes; but during peace the line would be available for ordinary traffic, and in this way it could be made to yield at least some return on the capital expenditure. The writer of this letter, Lieut. Arthur Walker, then an officer of the 79th Highlanders and the holder of a staff appointment at the School of Musketry, Fleetwood, followed up the subject by reading a paper on "Coast Railways and Railway Artillery" at a meeting of the Royal United Service Institution on January 30, 1865.[12] On this occasion he specially advocated the use of "moveable batteries" for coast defence in conjunction with railways constructed more or less within a short parallel distance of the entire coast line. Field artillery, he recommended, should be mounted on a truck the sides of which would be "encased in a cuirass of sufficient thickness," while the engine and tender would also be "protected by an iron cuirass, and placed between two cupolas for further protection." He considered that "to attempt to land in face of such an engine of war as this would be simply impossible." Moving batteries of this kind would be "the cheapest of all possible fortresses.... We have nothing to do but to improvise well-adapted gun-carriages for our rails." At the same meeting Mr. T. Wright, C.E., gave details of a proposed railway train battery for coast, frontier and inland defence which was designed to carry ten, twenty or forty guns or mortars. Another early advocate of the use of railways as an actual instrument of warfare was Colonel E. R. Wethered, who, in 1872, wrote to the War Office suggesting that heavy ordnance should be mounted on wheeled carriages so constructed that they could be moved along any of the railways, from point to point. In this way the three-fold advantage would be gained of (1) utilising the railway system for purposes of national defence; (2) rendering possible a concentration of artillery with overwhelming force at any given spot, and, (3) by the use of these moveable carriages for the conveyance of the guns, exposing the men to less risk.