PAPERS ON PHYSICS 295 
lt was the writer’s purpose to make a study of the possibilities 
of controlling indoor humidity of an ordinary furnace-heated 
residence located in central Illinois during a cold spell. 
The residence used for this study is a frame structure ap- 
proximately 22 by 42 feet, two stories, eight rooms, all rooms 
in daily use. The air supply for the furnace is fresh, outside 
air and is ample and the circulation is perfect. The abund- 
ance of air supplied the furnace prevents overheating; it is 
Fig. 1. The Humidifier 
a warm air system, not a hot air system. The humidifier con- 
sists of a seamless copper tray or pan, 18 by 36 inches (4.5 
square feet of evaporating surface) supported about 2 inches 
above the radiator and within the jacket. (Fig. 1.). The 
water for the humidifier is secured from the city supply and 
is controlled by means of a needle valve. The humidifier is 
provided with an overflow pipe. The furnace dampers are 
controlled by an automatic heat regulator which operates the 
dampers on a change of two degrees, or less, in the temper- 
ature of the living rooms. During this test the temperature 
was maintained at 70° at the warmest part of the living rooms, 
and about 65° at the coolest portions. 
The data were taken during the nine days from December 
20 to December 28, inclusive, 1914. This was probably the 
coldest week of that winter in this region. 
