STATE HORTICULTURAL SOCIETY. 77 



place as another provided the night is long enough. We know 

 the moderately elevated hilltop is warmer in the night time and 

 a,lways of more even temperature than the adjacent valley. Why 

 is this? Because being nearer to the cold regions it may be ex- 

 pected to first impart its surface heat; as this rises the warm air 

 of the hillside moves up, perhaps from all sides, forming a cur- 

 rent which may continue till the last warm breath is drawn 

 from the valley and this lingers longest on the hilltop while a 

 colder air has complete possession of the valley below. Now we 

 know these upward currents can not exist without corresponding 

 downward currents or a gradual settling of the upper air. Whilst 

 we incline to the opinion that in comparatively level sections 

 equilibriumis produced by the gradual cooling and settling pro- 

 cess we believe in more uneven sections quite strong downward 

 currents are often formed, which, like water, constantly seek a 

 lower level. Starting from high elevations of land all depres- 

 sions are filled, then down ravines to deep valleys and along val- 

 leys till dense woods or encircling hills stop or retard further 

 progress, then a raising up in a lake-like form till just the hill- 

 tops may remain like islands, or if the night is long enough the 

 whole region receives a thoroughly cold bath. 



Now while I believe results tend to prove the correctness of 

 the foregoing theories, I do not believe these upward and down- 

 ward currents are usually as distinct and forcible as I have in- 

 timated, but that like the whole question of climate they are 

 considerably mixed, i;ot only among themselves but by cross- 

 currents of wind, often so far above the earth's surface as to be 

 unknown to us. 



It has been my object to point as clearly as possible to the 

 best location for the apple orchard in Minnesota. And when 

 we find a change of temperature of seven degrees to eleven feet 

 or twenty-seven degrees to a few rods, this question of location 

 looms up and becomes paramount to all others and a thorough 

 knowledge of it seems to be a necessary preliminary to success- 

 ful experiment. For if we are told that some variety new or old 

 is hardf and productive, we must ask the question, where is it 

 hardy and producrtive? If it has succeeded for a series of years 

 in such unfavorable situations as a sheltered nook in a closed 

 valley or on the high level prairie, then we may entertain hopes 

 of its general adaptation, if otherwise, it is likely to prove a de- 

 lusion and a snare to rope in the unsuspecting granger. 



