Heavy artillery, wrote Adams, though the most formidable implement of modern warfare, had the disadvantage of requiring many horses to draw it. So the problem arose as to how the horses could be dispensed with. This could best be done, he thought, by putting artillery on "our true line of defence,--our rails," and having it drawn, or propelled, by a locomotive. "Mount," he said, "a gun of twenty tons weight on a railway truck, with a circular traversing platform, and capable of throwing a shot or shell weighing one hundred to one and a half a distance of five miles. A truck on eight wheels would carry this very easily, and there would be no recoil." Such a battery would be "practically a moving fortress," and, used on the coast railways, which he regarded as constituting lines of defence, would be "the cheapest of all possible fortresses--absolutely a continuous fortress along the whole coast." Communication with coast railways at all strategical points should, however, be facilitated by the placing of rails along the ordinary highways. After giving some technical details as to the construction alike of coast railways and road tramways, he proceeded:-- With these roads communicating with the railroads, the whole railway system becomes applicable to military purposes. The railway system is so especially adapted for defence, and so little adapted to invaders, that it should become at once a matter of experiment how best to adapt Armstrong or other guns to its uses. The process of fitting the engines with shot-proof walls to protect the drivers against riflemen would be very easy.... Nothing but artillery could damage the engines or moving batteries, and artillery could not get near them if it were desirable to keep out of the way. One gun transportable would do the work of ten which are fixtures in forts, and there would be no men to take prisoners, for no forts would be captured. The more this system is thought of the more the conviction will grow that it is the simplest mode of rendering the country impenetrable to invaders at a comparatively trifling cost. It will be seen that the scheme here proposed included three separate propositions--(1) the use of railways, as "engines of war," for coast defence; (2) the mounting of Armstrong or other guns on railway trucks from which they could be discharged for the purposes of such defence; and (3) the providing of the engines with "shot-proof walls" for the protection of the drivers. A similar protection for the men operating the guns on the trucks was not then, apparently, considered necessary; but we have here what was clearly the germ of the "armoured train." Among the other suggestions advanced on the same occasion were some for the employment of railways in general for strategical purposes, and more especially for the defence of London; and here, again, the employment of armoured trains was advocated.