A water-tube boiler for steam pinnaces and vedette boats designed and built by Mr. A. G. Mumford, Colchester, had been installed in eleven Royal Navy pinnaces. The boilers were constructed in elements, or groups of tubes, fitted into top and bottom headers, which were of forged steel, with one inlet in the bottom header, and one outlet in the top header. Any of the elements or groups of tubes could be disconnected and lowered into the furnace space and removed via the furnace front for repairs, without disturbing the remainder of the boiler, or necessitating the breaking of any joints, beyond the two connected to the element being removed. By removing the top and bottom covers of the tube headers a single defective tube in any position could be removed and replaced without interfering with the surrounding tubes. The boiler could be constructed with either direct through or return draught. The boilers supplied to the Royal Navy all worked with forced draught in closed stokeholes, and performed to the complete satisfaction of the Admiralty Authorities.