=Its Distance from the Work.=--As a rule, it may be stated that the first parallel is placed as near the work as possible. Most of the batteries of the second artillery position are from 100 to 300 yards in its rear, and the shorter their range the more effective is their fire. The small-arm fire from the first parallel may also be an important feature in modern sieges; to make it so requires the parallel to be located within 1500 yards of the work, if possible. By placing the parallel as near the work as possible, its length and that of the saps are correspondingly reduced, the amount of work lessened, and generally the fall of the place hastened. If an attempt be made to place it too close to the work, however, the working parties will be discovered; they will be within reach of strong sorties, and of the deadly fire of small arms and machine guns; in consequence of which they may suffer very great losses, be driven off, and the construction of the parallel prevented. The minimum distance under the most favorable circumstances is then about 600 to 700 yards. (This was the distance prescribed in the day of smooth-bore guns, and was adopted as recently as 1870 at the siege of Strasburg.) In an open, level country it may not be possible to place the first parallel at a distance from the most advanced work of less than 1800 to 2000 yards. When, however, it is necessary to establish the first parallel at a very great distance, it will not, as a rule, be made continuous, but in fractions covering approaches which are driven forward. The first continuous parallel is then built at from 1000 to 1200 yards from the works, and behind this the second artillery position is established. =80.= =Opening the Parallel.=--The profile of the parallel is one of those already given (Pl. I, Figs. 7-13), and it is traced and constructed as described (pars. 14, 18, and 19), by simple trench, flying sap, or full sap, as may be most advantageous. In some cases, however, it is constructed by enlarging the line of shelter trenches already made by the outposts. To cover the working parties while excavating the trench, when the parallel is near enough the work to be endangered by a sortie, the outposts are advanced to about 300 yards in front of the line, the pickets and supports are posted respectively at about 100 and 200 yards in their rear, and are covered by rifle pits and trenches made for this purpose during the preceding nights. To conceal from the defence, if possible, the proposed location of the parallel, these trenches and pits are constructed by all the outposts in front of their positions. The reserves are held 800 to 1000 yards in rear of the flanks, and the whole covering force should be equal to 1/2 or 2/8 the garrison of the place if an active defence is looked for.