March 8, 1889.] 



SCIENCE. 



179 



The area of cotton-culture has attained its present limits only 

 after many attempts to introduce it still farther north, where early 

 frosts prevent its being successfully carried on. At present the 

 northern limit of cotton-culture approximately coincides with a 

 mean January temperature of from 36° to 39° F. Even in the 

 southern districts of cotton-cultivation, it is greatly influenced by 

 the excessiveness of climate. While in the south of Spain the cot- 

 ton-plant is a perennial, it is killed in the United States every 

 winter by frost, and the plantations have to be renewed year by 

 year. But the American plant exceeds, in amount and quality of 

 its product, that of countries where the climate is more favorable 

 to its growth. Besides cotton, corn is grown to a considerable ex- 



We turn to considering the second zone of the Atlantic region, 

 that of corn. In North America corn-culture extends farther north 

 than in any other part of the earth. In more than two-thirds of 

 the eastern part of the United States it is the principal cereal 

 product. Its growth is favored by the heat and the suddenness of 

 precipitation in summer, the sky being generally clear, while rain 

 comes down during brief thunder-storms. The northern and west- 

 ern limit of corn-culture is not determined by the decrease of sum- 

 mer temperature and of precipitation, but by the increasing fre- 

 quency of early frosts in the fall, and late frosts in the spring. In 

 the valley of the Mississippi, corn ceases to be the most important 

 culture under the 43+ degree of latitude, where the mean tem- 



Wheat. Oats. Corn. Cotton. Suga 



.-\GRICULTUR.^L MAP OF THE UNITED STATES AND i 



tent ; but everywhere the former is the central point of interest to 

 the farmer, more money and labor being invested in cotton-planta- 

 tions than in any other culture. It is a remarkable fact, that corn, 

 although the climate is well adapted to its growth, does not give 

 nearly as good and rich harvests as farther north, where the cli- 

 mate is not so well adapted to its growth. The same is true re- 

 garding wheat, which gives the greatest and best returns near the 

 northern limit of its possible cultivation. In the cotton region, 

 wheat, barley, and rye are cultivated only in dry districts, in the 

 higher parts of the AUeghanies, and in the semi-arid region of 

 western Texas. 



Sugar-cane is not cultivated very extensively, as the cold of 

 winter hurts the young plants. It is only in the delta of the Mis- 

 sissippi that it is the prevailing culture, and in the adjoining parts 

 of Louisiana it reaches a considerable extent. 



perature of July amounts to 72°. 5 F. In eastern Ohio and Penn- 

 sylvania it hardly reaches the 40th degree of latitude, and in the 

 mountains of Virginia it does not extend beyond the 37th degree 

 of latitude ; while on the coast, where there are no late frosts, it 

 rises to the 44th degree of latitude. North of this line, early vari- 

 eties of corn are still cultivated, their northern Hmit being indicated 

 on our map by a broken line. North of this line oats take the 

 place of corn. In the West the corn region does not e.xtend nearly 

 as far north as in the East, on account of the greater frequency of 

 late frosts, which the young plant is unable to withstand. The 

 irregularity of the western limit is not caused by climatic differences, 

 but by the recent settlement of the districts. 



In this regfion wheat is cultivated extensively, but it is everywhere 

 second in importance to corn. In the humid, warm regions of 

 Delaware, in Tennessee, Kentuclcy, Missouri, Illinois, about three- 



