476 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1960 



acteristic pattern of fiber length distribution. The coefficient of fiber 

 length variability for the array of cotton fibers so removed from the 

 seed by hand, however, is exceeduigly small and its value may go as 

 low as 7 to 10 percent. Ginned lint possessing an exceptionally high 

 degree of fiber length uniformity has been observed to give a co- 

 efficient of length variability as low as 18 percent. Such uniformity, 

 however, occurs only rarely. For the general run of commercially 

 ginned lint appearing in domestic and foreign markets, below 27 per- 

 cent is considered a low length variability; 27 to 34 percent, average; 

 and above 34 percent, high. In the case of so-called "irregular, weak, 

 and wasty" cottons, which generally result from adverse growth con- 

 ditions or premature opening of the bolls by frost and subsequent 

 breakage of the predominant thin-walled fibers during ginning, the 

 coefficient of fiber length variability may go as high as 50 or 60 percent, 

 or even higher. 



Thus, with fibers in most short staple cottons varying in length 

 in diverse proportions from less than i/jg inch to 1 inch or more, with 

 fibers in long-staple cottons varying from less than 146 i^^h to as much 

 as 2 inches, and with fibers varying from less than 146 i^^ch to more 

 than 2 inches in extra long-staple cottons such as Sea Island growths, 

 the length factors and effects bound up in cotton quality become man- 

 ifold. Moreover, the fiber walls are collapsed in gi-eater or less degree 

 throughout the fiber length, lateral convolutions vary from almost 

 none to 500 or more per fiber, and the shapes and areas of the cross 

 section of tlie fiber are usually variable throughout its length. 



Even more amazing, perhaps, is the fact that the fiber length may 

 be as much as 4,000 or more times its width. To illustrate, if a 1-inch 

 cotton fiber with about average cross-sectional features were magnified 

 to a width of 1 inch, its proportionate length equally magnified would 

 be about 100 feet. And, if a typical 2-incli Sea Island fiber were mag- 

 nified to a width of 1 inch, its proportionate length would appear to 

 be about 400 feet. Incredible as these figures ma}^ seem, they il- 

 lustrate the extreme and unusual types of ratios with which textile 

 processing machines must deal when converting raw cotton fibers into 

 spun yarns. 



And, as if this were not complexity enough, cotton fibers attract and 

 give off moisture in continuous adjustment and readjustment to 

 changes in atmospheric humidity, writhing and curling in the process, 

 and varying their apparent length and the tenacity with which they 

 cling, one to the others, when spun into yarns. 



Over the thousands of years that cotton has been spun and woven 

 for man's use, a certain expertness was developed in selecting out and 

 describing cottons which possess in the aggregate, or mass, similar 

 quality characteristics; and it is a tribute to the genius of earlier 



