Fuel for Smudges. 113 



interruptedly from the hillsides, whence the cooled 

 air flows down into the valley underneath the smoke 

 and chills the plants. Damp straw, tar, turpentine, 

 old hay, anything that will result in the greatest 

 amount of smoke, will serve as fuel for these fires. 

 Have the fuel on the ground in advance, and start 

 the fires while the temperature is several degrees 

 above the danger point. 



"It is believed that decidedly better results will 

 be attained if damp fuel is used, or if the fire be 

 sprayed with water, for this will add vapor to the 

 air which, in condensing, will assist in checking 

 radiation by obscuring the sky with fog or cloud, 

 and at the same time the dew-point will be raised 

 to the temperature of the air. This plan should 

 result in absolutely preventing injury if the tem- 

 perature be much above the danger point, for the 

 condensation of the vapor will continue to distribute 

 heat throughout the space occupied by the mist. 

 In the case of smudge fires, the fire warms and 

 expands the air near it, causing it to rise. This 

 establishes an upward current of warm air from 

 the fire, which conducts the heat of the fire upward 

 and beyond the space needing protection, and cool 

 air flows in from the sides to take its place. Thus 

 the heat of the fire has but little effect in dimin- 

 ishing the intensity of the frost, almost the entire 

 protection being gained by the blanket of smoke 

 produced. By spraying the fire, on the other hand, 

 a large portion of the heat of the fire is consumed 

 in evaporating the water which, rising from the 



