The lantern consists of a rectangular copper housing in which two sets of mirror glass reflectors are arranged with their main (centre) mirrors parallel to the major horizontal axis of the burner, the mantle nozzles of which are arranged in staggered line formation, and are usually 12 in number. The two reflecting systems consist of a set of 3 curved glass mirrors fixed on a sheet metal back plate which is attached my means of hinges to the lantern casing. A simple positive adjuster permits rapid vertical focusssing of the controlled light beams between the angles of 70° and 80° and adjustment can be made to give up to 25° horizontal bias from each set of mirrors, whilst the lantern is designed to give a complete cut-off at 90° with the vertical. The air and gas adjusters are of conventional design, and are accommodated in the roof of the lamps where they are readily accessible. The construction of the lamp is such that complete access to the light chamber for maintenance purposes is obtained by opening the two hinged glass frames which form the lower lantern casing, and there are no interior fittings to hinder lantern cleaning.