batteries in the outworks of the fortress itself. With respect to the partial closing or entire destruction of the tunnel, both in its land and submarine portions, the Committee have entered into various details, and have made numerous proposals by which, if necessary, these objects may be accomplished. According to my judgment their recommendations, both as to defence and closure, are sound and practical, can be carried on without great cost or difficulty, and will amply suffice for the objects in view. I agree with them that the general line of the land portion of the tunnel had better be constructed not far from the lines of a fortress, whilst the exit should also be under the command of the guns of its outworks. Such a disposition of the tunnel will facilitate the arrangements in respect to the preparation of mines, etc., whilst a full command of the mouth will render its use or occupation by an enemy practically impossible. The various details and proposals of the Committee as to obstruction and closure, partial or permanent, are such as, I think, will commend themselves to engineers, civil or military, as being efficacious for the purpose; and I would further point out that whilst they are comparatively simple, it is evident they can be multiplied indefinitely, and have the further advantage, that the possession of the tunnel and its exit by an enemy would not prevent their being carried into effect; and even should some of them fail, such a contingency would not necessarily entail the failure of others. The means of obstruction, in short, are not only various but are independent of each other, and many of them could be improvised or multiplied even at the last moment. Nothing, indeed, is more obvious than the facility with which the tunnel can be denied to an enemy,
