ORCHARD HEATING 11 



accurate thermometers were placed inside the holes in the box 

 on different sides and at different elevation and one was hung 

 down in the center. Check thermometers were placed around 

 outside the box. As a mean of four experiments which had 

 been run from one-half hour to two hours after a steady state 

 had been reached the thermometers being read every five min- 

 utes, the box maintained a temperature of 14.1o F. higher than 

 the mean air temperature outside the box. A hose was attached 

 to a tank of carbon dioxide and this hose introduced into the 

 bottom -of the box through a hole in the side. This cold gas was 

 allowed to enter the box as fast as it would rim out of the 

 tank- The excess of temperature of the air inside the box over 

 that outside was now found to be 14.3o F. being but 0.2o F. 

 warmer with the gas than without it. Of course the gas that 

 entered was cold, due to its expansion on being liberated from 

 the tank. We 'next warmed the gas by surrounding the hose 

 with -warm water so that the gas entered the box at approxi- 

 mately the temperature of the air in this box- The mean raise 

 in temperature now was found to be 16. 9o F. This is now 2.8 

 F. warmer than without the gas. Twenty-two pounds of carbon 

 dioxide were liberated in the box in fifty minutes, making a 

 volume sufficient to fill it three times. At various times during 

 the experiment samples of air were extracted from the interior 

 of the box and the analysis of these showed an average of 3 per 

 cent of the air as carbon dioxide. Without the use of the carbon 

 dioxide it required 6y 2 watts per square foot to raise the tem- 

 perature IQ F. 



HEATING OF A SHELTERED AREA 



If heating be done in the court of a one story building, the 

 air space being open to the sky but surrounded by brick walls 

 we should get approximately the same result as that obtained 

 when many acres are simultaneously heated in the orchard be- 

 cause in this latter case heat is being passed both ways hori- 

 zontally from different heaters and in the inclosure the heat 

 that strikes the walls will in part be returned to the air space, 

 e- g., if one heater were placed in a room without a roof, the 

 walls would prevent the escape of the heat that struck them 

 and would reflect it back into the middle of it and yet the effect 

 would be the same if the wall were removed and another heater 

 was placed on the other side of it for now the heat that the wall 

 would have reflected back is supplied by the other heater. 



