ORCHARD HEATING 7 



fine spray to a distance just sufficient to cover very thoroughly 

 the entire tree. Eight standardized thermometers were placed 

 at various points in the treated section, always at the same 

 height above the ground- The same number were placed around 

 the outside of this section. A small, wooden shelter four inches 

 wide and a foot long was placed over each thermometer in order 

 to keep it dry, since it was hung in the branches of the tree 

 from which water was dripping as in the heaviest of rain 

 storms. Without any water being applied, the mean reading of 

 the thermometers inside the area in question was the same as 

 the mean reading of the check thermometers to within a frac- 

 tion of a degree, With the spray on two nights, the treated sec- 

 tion was found to be 0.5o F. colder than the air outside and was 

 the same both nights- The spray was left on until noon, and 

 although the air was warming up, yet the mean temperature 

 underneath the cloud was one morning l.lo F. colder than the 

 adjoining section and the other morning 2.5o F. colder, showing 

 that the cloud hung over the orchard did slightly retard the rate 

 of warming up when the sun arose in the morning; the effect 

 was very slight, however. A test showed that the air was prac- 

 tically saturated in the trees when the spray was on. 



On the night of April 14, 1912, a frost was experienced and 

 the spray was turned on. The apricots were in full bloom. Ice 

 as thick as one-fourth of an inch formed on the twigs and 

 branches and this weight was so great that the branches began 

 to break. A count of the damaged buds was made the next 

 night, and it was found that those on which the ice formed were 

 killed and that no fruit was obtained from this acre in the fall- 

 The apricots in the other part of the orchard were not damaged 

 by the frost at all, and a normal yield was obtained. The spray, 

 therefore, instead of protecting the orchard from frost, actually 

 damaged it. We had earlier observed in determining the injury 

 that had been caused to the fruit buds in the College orchard at 

 Logan after a night of freezing temperature associated with a 

 storm of sleet, that those buds that were open and were turned 

 up were frozen, while the majority of the buds that were turned 

 down and did not collect snow and sleet in them were not in- 

 jured. The same thing has been observed elsewhere since then. 

 Finer openings might have been made in the nozzle and the ap- 

 plication made higher above the trees, thus tending to merely 

 increase the humidity of the air by evaporation. These smaller 

 openings would become clogged because our equipment gave 



