These included steam engines from the London and Greenwich Railway that enabled the ships to make 4 knots on their own power, a unique combined steam-based heating and distillation system for the comfort of the crew and to provide large quantities of fresh water for the engine's boilers, a mechanism that enabled the iron rudder and propeller to be drawn into iron wells to protect them from damage, ships' libraries of more than 1,000 books, and three years' worth of conventionally preserved or tinned preserved food supplies.