When these difficulties had been more or less successfully disposed of and laying commenced, a minor but vital detail in the material threatened disaster. The cable coming forward proved to be mainly single D 5—_i.e._ the standard army cable as supplied for overground use in mobile warfare, when few lines are laid and there is no objection to the earth constituting the return circuit. The results already known to have been obtained by the enemy in picking up our messages through earth by means of sensitive listening telephone apparatus, had already caused the issue of stringent orders that all lines within 1,600 yards—later increased to 3,000 yards—of the front line must be metallic circuits—_i.e._ each line had to consist of a pair of insulated wires. Also, owing to inductive effects when a number of pairs of wires are laid closely parallel to each other, as in a trench, a conversation over one pair will be heard in the other circuits unless each pair is twisted. The use of the single cable, therefore, not only doubled the work of laying (as each line necessitated two separate wires), but the untwisted pairs so formed would render the lines noisy and possibly entirely unworkable. Utilizing the frame of a cable wagon trail, and one of its wheels as a foundation, a machine was rapidly improvised by the section on which the drums of single cable were mounted as received, spun into twisted cable, and simultaneously reeled off on other drums for the laying parties. This apparatus was kept going and running at high pressure by the section wheeler, Sapper Page, with a few Artillery Headquarters’ grooms and batmen as his only available assistants. By such strenuous efforts the programme was completed, and when the preparatory bombardment opened, 500 miles of cable had been laid and joined up in over twenty miles of cable trench, and every battery had excellent and reliable communication forward to its observation posts and back to its group commander. Two dug-outs had been constructed on each flank, into which all O.P. lines were led and terminated on special switchboards, designed and made up at the Company Headquarters. Through these O.P. exchanges any battery could be connected to any O.P. for control of fire, which proved most valuable in the changing circumstances of the fighting. At that date the establishment of neither groups nor batteries included switchboards for metallic circuit lines. The necessary number—over thirty—were improvised in a few days at the Company workshops out of electric light fittings purchased in Amiens.