This intact boiler, one of the two preserved examples, provided the necessary steam required to operate the press engine and other processing equipment. The holes on the end plates suggest that the steam was supplied by a system of horizontal return tubular (HRT) fire tube boilers. Each opening was connected by a horizontal tube to its counterpart on the opposite end. Heat was conducted from the externally-fired dutch oven through each tube via a flue on the back end of the combustion chamber. The multiple tubes created a large surface area for heating the surrounding water within the sealed boiler. At least 114 openings can be counted on one intact boiler end. Deerr (1911:404) calculated that a seven foot diameter boiler with 120 tubes can supply 1800 ft² of heating surface.