[Illustration: FIG. 23. Interior of No. 1 brooder house showing walk and hover combined in the middle of the house and pens on each side. (_Photograph from the Bureau of Animal Industry, U. S. Department of Agriculture._)] _Heating Apparatus._ Heat is furnished by means of a coal burning stove which heats water and causes it to circulate through pipes run the length of the house. The heater must always be placed in the windward end of the building as otherwise it is hard to get the heat down to the other end as the wind tends to drive it back. The hot water pipes are carried down the center of the house and the return pipes are located in the same place. A low partition is run lengthwise of the house dividing the pipes and thus forming double pens, half extending from the center to the front and half from the center to the rear of the house. The pipes and the partition between them is covered over with boards making a 4 foot walk or runway directly over the pipes, which comes into most convenient use as a place to convey, by means of a wheelbarrow, feed or other material needed in the house, and as a convenient place from which to care for the ducklings in the pens on each side. This board covering over the pipes also serves to hold the heat and thus forms hovers. It is advisable to partition off the first third of the house, that is, the portion in which the heater is located, with a solid partition. Then by having suitable valves in the pipes, the heat can be cut off from the rest of the house and only the smaller partitioned off end used as a separate and independent section of the brooder. This is especially useful when only a small number of ducklings are being hatched early in the spring when the weather is cold and it may be difficult to heat the whole building properly. It is also economical in fuel under such conditions. If, on the other hand, the number of ducklings hatched during the cold weather is so large that all or nearly all of the house capacity is needed to care for them, it will usually pay to install an additional heater, the pipes from which can be run along the rear wall of the building, in order to keep up a proper house temperature when the weather is severe.