THE SUB-TROPICAL ZONE. 119 



treated as an annual. The best plants yield 

 about two and, a half pounds of clean cotton, 

 the weakest only about five ounces. They re- 

 quire to be kept free from weeds, especially 

 from the species of convolvulus, or ipomsea, 

 which would speedily choke them, and, espe- 

 cially in Brazil, are very luxuriant. The col- 

 lecting of the ripe cotton capsules is a very 

 laborious work, and requires a great many 

 hands in a large plantation ; the harvest lasts 

 for several weeks. The greatest difficulty is the 

 separation of the cotton from the seeds ; in 

 America this is effected very completely and 

 expeditiously by machinery, but in India by 

 hand. Cotton appears to have been known to 

 the ancients. Herodotus mentions cotton gar- 

 ments 445 years before the Christian era, and 

 the Mexicans manufactured cotton cloth prior to 

 the discovery of America. Its importation into 

 Great Britain has increased with extraordinary 

 rapidity of late years, and to an extent almost 

 unexampled in the history of commerce. In 

 the seventeenth century, the trifling supply re- 

 quired was obtained wholly from Smyrna and 

 Cyprus. In the year 1786, about 20,000,000 

 pounds were imported. In 1838, the quantity 

 was upwards of 500,000,000 pounds ; and in 

 1848, the enormous quantity of 712,554,080 

 pounds were imported into this country ; while 

 the quantity of cotton rn^inufactures exported in 

 the year 1848, was of the value of 16,770,868 ; 

 and of cotton spun into yarn, 5,927,956. 

 The quantity of cotton manufactures, ex- 



