COTTON STRUCTURE 263 



cloth. Therefore, to secure the best grade and price, bolls 

 of cotton should not be picked until well opened, thus 

 giving an opportunity for sun and air to mature the fiber. 

 The value of cotton fiber is determined by (1) length, (2) 

 strength, (3) maturity, (4) fineness, and (5) uniformity. 

 The longest fiber is usually the finest, and such fibers may 

 be used in the manufacture of the finest, thinnest, and most 

 expensive cotton fabrics. 



The following are approximately average lengths of the fibers 

 of the principal kinds of cotton : 



Sea Island, 1.61 inches ; 

 Egyptian, 1.41 inches ; 

 American upland, 0.93 inches ; 

 American long-staple, 1.3 inches. 



The fiber is longest on the larger or upper end of the seed. 



The average diameter of American upland short-staple cotton 

 is TsW to yjsVff inch. The cotton fiber attains its maximum length 

 before reaching its maximum diameter and strength. 



Williams (N. C. Bd. Agr., Bui. Sept., 1906) found that in 12 

 varieties of cotton, the average weight required to break a single 

 fiber was 6.83 grams. Hilgard found the extremes of breaking 

 strength of cotton to be 4 and 14 grams. Cotton is about three 

 times as strong as wool in proportion to the size of fiber. In a 

 pound of Russell cotton there were calculated to be more than 

 15,000,000 fibers, which, if placed end to end, would make a line 

 about 2000 miles long. Cotton fiber is prevented from readily 

 absorbing moisture by an oily covering of each fiber, which is 

 said by Monil to make up about 2 per cent of the weight of the 

 fiber. Absorbent cotton represents cotton from which this oily 

 protection has been removed by treatment with chemicals. The 

 oily covering must be removed before the yarn can be dyed. 



It is thought by farmers that if seed cotton be stored for some 

 time before ginning, the proportion of lint will increase and that 

 it will then make a better-looking sample. If this be true, there 



