The selection of the positions for machine guns in permanent works belongs to the art of the engineer, and there is little that can be said of their tactical employment. Fire should be reserved until the attack has reached close range, and then only opened when the target is large and vulnerable. Guns must be concealed by every possible device and all the loopholes must be blinded. By night all guns should be mounted and trained to sweep ground by which the enemy must approach; when search-lights are not in use, the elevation should be checked by the use of a clinometer and the amount of traverse may be shown by chalk lines on the parapet, or white stones placed in two rows. In this way accurate fire may be brought to bear on the assault on the darkest night, and many night attacks were repulsed with machine-gun fire by the Russians at Port Arthur. Sir G. S. Clarke says: “The front faces of the forts were retrenched in some cases by obstacles and a line of field parapet across the terre-plein. _These, with the assistance of machine guns brought up at the last moment_, enabled assaults of the breaches formed by the mines to be repulsed.” Again, “The Russians used machine guns with effect, frequently concealing them in light blindages, so that their positions could not be detected until they were brought to bear upon an attacking force.” The war correspondent Mr. F. Villiers, in his book _Three Months with the Besiegers_, speaking of the storming of West Panlung Redoubt,[40] says: “The death-dealing machine guns of the Russians _in the casemates of the fort_ are playing ghastly havoc--such havoc that only a score or more of Ouchi’s battalions reached the first ditch of the fence, where they threw themselves panting into the grateful cover of the pits their own artillery have torn.” The number of machine guns allotted to the permanent works of Port Arthur is given as 38 by the United States Official Report, while Nojine, in _The Truth about Port Arthur_, gives them in detail as 28, the distribution of which is shown in red figures on the map at the end of Chapter IX. The ten guns unaccounted for were probably mobile, and used for the defence of the harbour and the various landing-places in the neighbourhood of the fortress.