Flues
The system of fixing Flues for heating purposes in glass structures is now become nearly obsolete, the better and more effective mode of heating by hot water being almost exclusively adopted. In the earlier days of gardening, the use of Flues was general, and even now many remain and continue to answer their purpose exceedingly well, both for fruit and flower cultivation. Flues may be constructed of bricks, and covered with thick flat tiles or slates, placing a cross piece of sheet iron under each joint; or large pipes may be employed with good results, if properly connected. Fire bricks should be used near the furnace, and the Flue proceed from here round the front part of the house first, returning at the back, or terminating in a chimney at the end, according to the amount of heat required. Corners should be turned by a curve, to allow the heated air and gases to pass more freely, and consequently prevent cracking of the joints. The whole of the heat transmitted to the house must pass through the material used in the construction of the Flue; and all holes or cracks should be kept stopped, to prevent the escape of smoke and injurious gases. It is very important that Flues be kept cleaned out, as a coat of soot prevents the absorption and free passage of heat, and is also and obstruction to the draught. The furnace is best near one end of the house. It should be placed about 2ft. below any part of the Flue, and a gradual ascent allowed the latter until the chimney is reached.