THE STRENGTH OF TEXTILE PLANT FIBERS. 

 Table I. — Tensile strength of eotton fibers . 



19 



Variety of cotton. 



American Upland (Gossypium hirsutum): 



Big-Bon Stormproof group 



Big- Boll CTOup 



Cluster group 



Semicluster group 



Peterkin group 



Early group 



Long-staple group 



Sea Island ( Gossypium barbadense) 



Egyptian (Gossypium barbadense): 

 From Arizona and California 



Breaking strain (grams). 



The highest and lowest figures given in the foregoing table are the 

 averages for 20 fibers, not the highest and lowest breaking strain of 

 single fibers. The tensile strength of single fibers of American 

 Upland cotton is generally in inverse ratio to their length, though 

 the longer staples make stronger yarns. The strength is in more 

 direct ratio to the diameter. The accurate measurement of the 

 diameters of the twisted, ribbonhke cotton fibers presents such 

 difhculties and requires so much time that it is not mcluded in all 

 tests. Measurements by means of a microscope with an eyepiece 

 micrometer have been made of more than 100 samples. A summary 

 of these measurements is shown in Table II. 



Table II. — Diameters of cotton fibers. 



Variety of cotton. 



Diameter (microns). i 



Maxi- 1 Mini- 

 mum. 1 mum. 



Average. 



American Upland (short staple) . 



Sea Island 



Egyptian (American grown) 



3L88 

 24.31 



23.30 



1 1 micron=0.001 millimeter, or nearly 0.00004 inch. 



A series of tests has also been made to determine the pull necessary 



to detach the fiber from the seed. In American Upland varieties this 



ranges from 1.88 to 2.3 grams, and in Sea Island from 1.75 to 1.95 



grams. 



STRENGTH OF LONG FIBERS. 



The long fibers constitute two natural groups: (1) Soft fibers, or 

 bast fibers, such as flax, hemp, jute, and ramie; (2) hard fibers, such 

 as abaca (Manila hemp), henequen, sisal, and phormium (New Zealand 

 hemp). The strands of the soft fibers vary greatly in thickness and 

 thev usually cling together in such a manner as to make it practically 



[Clr. 128] 



