Description | View of open trench with descaling machine; legend "Internal Cleansing of Main by General Descaling Co Shows apparatus used by General Descaling Co for revoving the flexible steel rods inside a gas main for the purposes of loosening up the internal corrosion which is subsequently washed away by means of o flow of water. Note in the background the sludge pump and to the left of it a pile of corrosion taken from the main"; Ref M196; dated November 1948 |