HEATING PLANT FOR A LILY POND. 85 



boiler to the piping in the tank. The flow mains rise from the side of the 

 boiler, which is of the sectional type, and run on a brick foundation inclosed in 

 a wooden box to the Lilj- pond. 



On reaching the pond the two flow mains have a stand-pipe, which serves 

 both as an air vent and an expansion pipe. From this point the piping has a 

 fall all the way back to the boiler. After passing the standpipe the flow main 

 drops down and runs around to a point near the main Lily bed where it 

 connects with a Y, from which two four inch pipes are run around the pond, 

 turns being made by means ot 45° ells, as shown. On reaching the point 

 where the return main leaves the tank, the two four inch pipes are connected 

 into a Y and from it to the return main. This method of piping is followed in 

 each end of the pond. 



The requirements laid down by the Park Commissioners were that a tem- 

 perature of 90° should be maintained in the water, regardless of the tempera- 

 ture or amount of water that it might be necessary to turn into the pond. The 

 fires are first lighted early in June. The water, which had been taken from 

 the street mains to supply the pond and change the water in it, has varied in 

 temperature from 40° to 50°, and the specified temperature in the pond has 

 been readily maintained, sometimes running as high as 96° when the weather 

 ■was bright and clear and the sun strong. 



When an outlet at one end of the pond draws off the hot water to reduce 

 the temperature, cold water is brought in to restore the proper temperature 

 and level. 



An overflow pipe is provided at each end of the pond to prevent the water 

 rising above the desired height. In operation it has been found that it is only 

 necessary to attend to the fire in the boiler twice a day, and in damp, dull and 

 cloudy weather, when little heat benefit is derived from the sun, no difficulty 

 has been found in maintaining the temperature at 90° or higher, with the 

 water in the flow main seldom exceeding 120°. The water in the pond is 

 heated by contact with the pipes, in order to avoid a deposit of mud in the 

 boiler that would be probable with the water in circulation, owing to the earth 

 for the plants in the pond and the dust that would blow into the pond and 

 settle, both of which would be carried into the boiler. 



