TEMPERATURE OF THE COTTON SEATES. 61 



those parts where this percentage is 10 and above have a summer rain- 

 fall beloiv 14 inches, and a winter rainfall above 12 inches. 



Temperature. — The distribution of heat in the cotton States is 

 nearly normal, as the isothermals follow approximately the i^arallels of 

 latitude, the departures from this regularity being due (1) to the heat- 

 ing effect of the Gulf Stream, by which the lines of equal temperature 

 are elevated or deflected northward along the Atlantic coast j (2) to 

 the cooling effect of the mountains, which causes a depression south- 

 ward of these lines, as may be seen in the vicinity of the Appalachians; 

 and (3) to the accumulation of heat in valleys, which carries the iso- 

 thermals up these valleys, often to considerable distances beyond their 

 normal position. With these general principles in view, it will be easy 

 to understand the temperature distribution in the region of which we 

 are writing. 



The mean annual temperature line of 6S° Fahr. runs nearly parallel 

 with the southern coasts of Alabama, Mississippi, Louisiana, and Texas, 

 where these coasts have an east and west direction, and at no great dis- 

 tance north of this shore line. In Texas it is carried up the Eio Grande 

 Yalley, beyond the 102d degree of west longitude. 



The line of 64P follows approximately the parallel of 33o^ running 

 north of it near the coast in North and South Carolina, because of the 

 Atlantic Ocean; south of it in Georgia and Alabama, because of the 

 influence of the Appalachian chain ; it is carried upward by the Missis- 

 sippi and Eed Eiver Valleys, bending downward on each side of them, 

 being deflected far to the south beyond Eed Eiver, in Central Texas, 

 by the influence of the western mountains. 



The line of 60°, starting from the coast of IN"orth Carolina a little 

 north of the 3Gth parallel, crosses that State diagonally to the eastern 

 fgot of the Appalachian range, around the southern end of which it 

 sweeps in a great curve which passes below Talladega in Alabama, and 

 bends northwestward to ISTew Madrid, Mo., whence it runs westward 

 approximately along the 36th parallel through the Indian Territory 

 into Texas, till turned southward like the preceding in the western 

 part of that State. 



The isothermals between 52° and 56^ lie generally north of the cot- 

 ton States, except in the Appalachian region of ISorth Carolina, Ten- 

 nessee, Georgia, and Alabama, and the central parts of Tennessee and 

 Kentucky, but in none of these localities is the production of cotton 

 on any large scale, except in Western IN'orth Carolina, the valley of the 

 Chattahoochee in Georgia, that of the Tallapoosa, Coosa, and Tennes- 

 see in Alabama, and a part of the central basin of Tennessee, where 

 the mean annual temperature is between 56° and 60°. 



The isothermals for the summer are far less regular than those of the 

 year. Thus the summer line of 80°, starting at the coast near Charles- 

 ton, runs westward to Macon, Ga. ; thence south to Tallahassee, Fla. ; 

 thence diagonally across Alabama to Tuscaloosa, to which it is raised 



