40 NORTH CAROLINA THERMAL BELTS. 



"The flora is grand. The azalea there, instead of being a shrub 

 four feet high, attains a height of 10 to 20 feet, and exhibits every 

 shade of pink and orange. 



a We are in latitude 35, but for all practical purposes 3 south of 

 our geographical position. The leaves of plants, shrubs, and flowers 

 remain untouched by frost until the latter part of December, and 

 sometimes till the middle of January, when they are killed by snow 

 or sleet. The early spring in the belt admits of planting any vegeta- 

 bles the first of February without risk from frost. Tomatoes, tobacco, 

 and other tender plants remain green until after the middle of De- 

 cember. Fig trees live through the winter unprotected, and bear full 

 crops, while in the valley they are killed to the ground every winter. 

 Grapes never mildew nor rot, and are of large size and delicious 

 flavor. This belt is confined within distinct and well-defined limits, 

 which remain the same from year to year, and in the middle stratum 

 of air or land on the mountainside." 



Another writer says: "After a snow-storm not a particle of snow 

 will exist in the belt (it melts as it falls), while the tops and sides of 

 the mountains above, and the valleys below, will be covered. 7 ' 



Prof. John Le Conte said : "I wish to put on record the results of 

 observations made by me many years ago on the 'frostless zones 7 of 

 the flanks of the mountain spurs adjacent to the valleys in the Blue 

 Ridge. My observations were made at Flat Rock, near Henderson- 

 ville, Henderson County, a well-watered, fertile, mountain plateau- 

 like valley, which is about 2,200 feet above the sea-level. 



"My own observations, and the information elicited from resi- 

 dents, seem to indicate the following facts : The zones in question 

 are not exempt from frost during the whole of the cold season ; in fact, 

 during the winter the ground in these belts is frequently frozen to a 

 considerable depth, but during the spring months they are conspicu- 

 ously and uniformly frostless." 



It seems, then, to be an established fact that, at these three points, 

 in three different counties, there are some noteworthy meteorological 

 conditions prevailing along this belt of 400 to 1,000 feet of perpendic- 

 ular height, and it seems probable that a similar state of things exists 

 in kind, if not in degree, on all the southern and eastern slopes of 

 parallel mountain ranges in that latitude where protected against 

 wind. 



Respecting the explanation of these phenomena, Mr. McDowell 

 theorizes as follows : "Heat is ever radiating from the earth, and in 

 cold, clear, still nights it mounts upward through the cold, damp 

 air, taking from it its caloric, while the latter rushes down in a cold, 

 frost-producing current, and hence the lowest ground in a valley is 

 ever subject to the hardest frosts. 



"The warm, dry, light current keeps mounting upward like cork in 

 the water, until it reaches a stratum of atmosphere too thin and light 

 to support it, when it consequently falls back and pours its warm, dry, 



