PROTIiCTING ORCHARDS AGAINST FROSTS. 277 



the warm air does not rise but is carried off in a horizontal 

 direction. On this account more success will attend the heat- 

 ing of orchards when the air is slightly in motion than when 

 perfectly quiet. Furthermore, when the air is moving rap- 

 idly conditions are unfavorable for the formation of frost. 



Tims it will be seen that cold, still nights are the ones the 

 fruit grower dreads because of the danger from frost and the 

 greater difficulty of heating the orchards. In Missouri there 

 are not many orchards of much consequence that are planted 

 in low ground. However, judging from results obtained in 

 Colorado, it would be quite possible to heat the valleys to a 

 sufficient extent to save the flowers or young fruit from being 

 frozen. But if the area were small and consequently only a 

 comparatively small number of heaters used, it would be 

 quite difficult or even impossible to raise the temperature 

 high enough. ^A^ith an area of twenty to forty acres in a 

 block in a valley, properly heated throughout, there would 

 be very few times, if any, when the crop could not be saved. 

 Upon high ground, as has been seen, even though the surface 

 be rough, the heat will not flow down hill, but escapes upward 

 or is carried off along the ground by the wind. 



In Missouri there will be few seasons, indeed, when raising 

 the temperature as much as five degrees would not save the 

 crop. Of course the higher the ground where the orchard 

 stands, the less the danger from frosts and the fewer the num- 

 ber of degrees it v/ill be necessary to raise the temperature to 

 save the crops. For example, there have been many times in 

 south Missouri when, if the temperature could have been 

 raised two degrees on the hilltops, the crops might have been 

 saved. On the same occasions it would have been necessary 

 to raise the temperature perhaps five or six degrees on adjoin- 

 ing land with an elevation of one hundred feet less. 



By using from 75 to 100 oil pots per acre, if the orchard is 

 fairly well elevated, it should not be difficult under conditions 

 that usually prevail in Missouri to raise the temperature 

 from two to four degrees. This will generally save the crop. 



