Model of a tubular boiler
This steam boiler has a funnel that could be retracted under sail. There are two doors to the smoke box in the sides and three to the furnaces in the centre. Steam was heated in the boiler by a series of small fire-tubes. Advances in technology made it possible to fit steam boilers with increasing numbers of these tubes. This model has 176 of them, which significantly reduced the size of the boiler and enabled it to be installed below the waterline.