REPORT OF CAPT. GEORGE B. M'CLELLAN. 31 



Each relief is relieved after filling 18 gabions, wliicli should be accomplished in 3 hours. 



The 1st sapper fills 3 gabions, and then becomes No. G ; No. 2 becomes No. 1, &c. The end 

 of the sap roller is on the alignment of the exterior surface of the gabionade. The joint between 

 the sap roller and the gabion in the course of being filled is not covered ; the next 12 joints are 

 each covered by 2 sand bags on end ; after that with sap fagots. 



Temporary crowning fascines are not habitually used. 



Execution of the single sap. — The 1st sajiper leaves a berm of 1' ; his form is 18" deep, 1' wide at 

 bottom ; base of berm slope 1' ; he works on his knees. The 2d sapper follows No. 1 at the distance 

 of 3 gabions ; his form is 2' deep, 2' wide at bottom, berm slope f ; he throws his earth over the 

 gabionade, and works on his knees. The 3d and 4th sappers crown the gabions opposite their 

 forms with one layer of 2 fascines, and then complete their respective forms, preserving the berm 

 slope off ; the form of No. 3 is 2^' deep by 2|' wide at bottom ; that of No. 4 is 3' deep and 3' 

 wide at bottom. Each sapper follows at 3 gabions behind the one in front of him. In the 

 meantime, Nos. 5 and 6 pass up the materials, place and secure with pickets the 2d layer of 

 fascines, remove the sand bags from the joints, and replace them by saj) fagots. 



Nos. 2 and 3 manoeuvre the sap roller. 



Boyaux made by the single sap are 6' wide at bottom. 



Douhle saj). — This is 12' wide between the two rows of gabions. Its trench, when completed, 

 is 10' wide at top, 6' at the bottom. The head is covered by two ordinary sap rollers, not 

 united in any way, the joint being closed by sand bags, or a wool bag. If it is necessary to 

 throw the sap rollers further out than usual, the opening left between them may be covered by a 

 short sap roller. 



The covered sap. — In this, blindage frames are used, each consisting of two stanchions 10^' long 

 X 7" square, and of two cross pieces, the upper of which is 10" X T", the lower 7" X 5". 

 The frame is 4' wide from out to out, and 7^' high from out to out of the cross pieces. The 

 stanchions project equally beyond both cross pieces, and have points 9" long. The frames rest 

 against the berm slope, having its inclination. Two cross beams, each 16' long and 10" X 7", 

 rest on each top cross piece. Five longitudinal beams of a similar section are laid on the cross 

 beams ; on top of these two layers of fascines, and on top of them 3' of earth. The trench thus 

 formed is 7' high in the clear and 6' wide at bottom. In pushing the sap from the crowning 

 of the breach, the first sapper makes his from 3' deep and 2' wide at bottom ; each of the other 

 sappers widens and deepens it 1'. 



MINES. 



Frames of grand galleries are 6' high and 3' wide in the clear. 



Frames of common galleries are 4^' high and 3' wide in the clear. 



Frames of branches are 2^' high and 2' wide in the clear. 



All parts of the frames are 5" wide ; the caps are from 5" to 9" deep, the sills from 3" to 5" deep. 



For branches, the width and dej)th are diminished 1". 



The frames of Dutch galleries are of 2" plank, and from C" to 9" wide. 



Each party of miners consists of three non-commissioned officers and eighteen men, divided 

 into three reliefs, each relief working six hours. In ordinary soil, where no unusual obstacle 

 is encountered, each relief should drive from 3' to 4' in six hours. 



In defending any position by field works, the system pursued was to occupy the flanks and 

 other important points of any given line by redoubts, lunettes closed or palisaded at the gorge, &c., 

 afterwards connecting them by continuous lines if time was afforded, and the locality ren- 

 dered it advisable. When circumstances were favorable, the command of the works was usually 



