154 MILITARY SCIENCES. 



redoubts of open and inclosed works, which we have repeatedly mentioned, 

 we devote some separate drawings to their illustration. Fig. 53 shows the 

 section, jig. 52 the view,j^^. 51 a part of the ground plan of a small block- 

 house, and jig. 49 the view, jig. 50 the section of the block-house in jig. 44. 

 Upon piles, driven into the earth, sills are laid, and upon these the walls are 

 formed of trunks of trees from ten to twelve inches thick, placed close 

 together, side by side, and loopholed. The entrance is on the side most 

 remote from the enemy. Inside there are two or three rows of posts, 

 according to the depth of the block-house, which support the roof-frame 

 joists, on which is then laid a double layer of beams, crossing each other in 

 close contact, and projecting on all sides over the inclosing walls. Upon 

 these beams comes a layer of earth to render the building bomb-proof. 

 Inside, wooden bunks are placed for the accommodation of the garrison. 



Fig. 42 shows a front of attack in a bastioned line, with a block-house as 

 redoubt. The place-of-arms of the covered way, in the re-entering angle, 

 is rounded, and the faces of the covered way cremailliered. Fig. 44 is a 

 lunette, having its gorge closed with palisades and with a block-house there, 

 as redoubt. The salient angle of the counterscarp contains a subterranean 

 block-house for the defence of the ditch. Fig. 43 is a profile through the 

 face of jig. 42, and fig. 45 the profile through the face of jig. 44. In both, 

 the disposition of a subterranean powder magazine is indicated. Figs. 46 

 and 47 show the profile and elevation of the block-house for defence of the 

 ditch, with the subterranean passage leading to it, and jig. 40 is the profile 

 through the bridge, ^^. 42, with passage (postern),/, through and under the 

 parapet to the covered way, k. Fig. 37 represents the interior arrange- 

 ment of a principal fort. Under the platform. A, in the re-entering angles 

 of the four posts, lie the powder magazines, P. In the interior space of the 

 work is the bomb-proof block-house, B, for the garrison, and within it the 

 kitchen, K. Fig. 39 gives a profile through the broken line, ik, jig. 37, 

 from which the internal arrangement of the block-house is to be seen. 

 Fig. 38 is a profile, along GH, through the block-house and the powder 

 magazine. Fig. 40 is the bridge and entrance postern, in section, along 

 the line, s^, in /^. 37, and jig. 41, a section of the kitchen along gg, 

 jig. 37. 



/i. Powder Magazines. Powder magazines, always subterranean, are 

 disposed too under that part of the rampart least exposed to attack, as in 

 pL 47, jig. 44. They are made dry by means of frame pieces and board 

 revetments. Fig. 48 shows the ground plan of a small, and jig. 55, of a 

 large powder magazine. Fig. 56 gives the section of jig. 48, and j^^. 54 

 that of jig. 55. It will be perceived that the entrance does not lead imme- 

 diately into the magazine from without, but that, by means of a gallery 

 disposed for that purpose, it is secured against the direct fires of the enemy. 

 The height of the interior under the frame-piece is six feet. 



2. Permanent Fortijication. 



The old manner of fortifying by means of long straight lines with towers 

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