The accompanying sketch shows a small heater 8 in. by 6 in.,with about 9 ft. of £-in. pipe attached. There is an air valve on top of the heater, and a small filling cistern is connected to the return pipe. This would fail owing to air in the pipes, and it must be difficult to fill the pipes without locking air in with the pipes arranged as shown. Putting an air pipe to each pipe at the point marked with an asterisk at A should prove a remedy, these two air pipes either going up separately or joining together, but in each case they must go as high as the little cistern. This point should be the highest point in the circulation, the flow pipes from the top of the boiler rising, say, 1 in. to the air pipes, and then descending lin. from this point towards the cistern connection.

Heating Chicken Rearer.