31. The security of our great arsenal of Woolwich demands (independently of any plea of metropolitan defence) that this important position should be occupied by a work of considerable strength. Such a fortress would answer three purposes, each of them of paramount importance! In the first place, it would remedy the extremely insecure state, and to an enemy the most tempting defencelessness, of our greatest military manufactories and arsenal; secondly, it would, by means of its outworks, effectually bar the Thames from any gun-boat attack; and thirdly, it would form one of the angles of our great polygon of positions for the defence of London. The next of these angles would be at the spur of Norwood Hill; where it would be necessary to construct a considerable fort. The third permanent work would come in the immediate vicinity of Wimbledon, where the range of hills again spurs out to the South; and these three would complete the salient angles of the southern half of the defence of London. Probably two works of a like nature would suffice for the northern division; and a third might be added in the direction of, and perhaps either within range of, or covering Enfield Lock, the great rifle factory for the Army. 32. These five or six forts should be regular permanent works, and of sufficient importance to be secure against a _coup de main_: in fact, to compel an enemy to sit down before them for a siege of greater or less duration. They should all be armed with heavy long-range guns, and should besides contain surplus stores of both guns and ammunition for the armament of other works, to be hereafter described. 33. Such would be all the extent of fortification necessary to be undertaken at first; but to complete the chain, it would be requisite that plots of ground should be acquired in suitable positions: generally, one between each of the permanent forts; and on each of these pieces of ground should be carefully traced the outline of an earthen work, of extent and form to suit each particular case. 34. The execution of these works could be undertaken by the garrisons of the permanent works, which would be relieved from time to time. They would thus form a series of military industrial schools, in which a large proportion of our troops might learn the all-important and much-neglected art, how to use a spade in their own defence. Perhaps some of our volunteers would not be above taking a few lessons of the same kind. Such as have formed themselves into engineer corps would of course do so, and we should thus be able to place another important mode of defence in the hands of these gentlemen. The outworks of the main forts, indeed, might be executed by the same means, and they could thus be kept continually being increased in strength.