14 FRUIT-GROWING 



Another advantage in locating the orchard 

 on a slope is to secure the benefit of "air drain- 

 age." Many persons do not realize how easily 

 cold air slides down-hill. It goes down, of 

 course, because it is heavier than warm air, and 

 on a quiet night one can go out on a hillside 

 and feel the current of cool air rushing down 

 into the valley. I suppose in this motor age 

 every one has experienced the sensation of rid- 

 ing in a machine at night along a road leading 

 from a hill into a valley and noticed the dif- 

 ference in the temperature between the 

 elevations. 



This difference in temperature is of a very 

 practical value to the orchardist and frequently 

 makes all the difference between a full crop and 

 no crop at all. 



Here at Hickory Hill we have a government 

 weather observation station with recording 

 thermometers both on top of the hill and in the 

 valley. The difference in elevation is one hun- 

 dred and sixty-eight feet and on still nights 

 the temperature will vary as much as fifteen 

 degrees. Frequently I have seen the peach 

 crop a failure below a certain definite altitude 

 on the hills. One spring when the peaches 

 bloomed we could see a regular contour line 

 following around the hills. Below this line 

 there was no bloom while above it the trees 

 were filled. The line was so sharp and distinct 



