Agricultural chemistry — agrotechny. 



313 



The results of a large number of tests of samples are summarized below ; 

 TensUe strength of cotton fibers. 



Variety of cotton. 



Breaking strain. 



Highest. 



Lowest. 



Average. 



American Upland (Gossypium hirsutum): 



Big-Boll Stormproof gi^oup 



Big-BoU group 



Cluster group 



Semieluster group 



Peterkin group 



Early group 



Long-stapie group 



Sea Island ( O. barbadense) 



Egyptian (G. barbadense) from Arizona and California 



Grams. 



9.0 

 11.6 

 7.7 

 7.1 

 6.0 

 6.9 

 5.6 

 7.6 

 8.0 



Grams. 

 5.2 

 4.6 

 5.1 

 4.7 

 5.0 

 5.2 

 3.5 

 4.7 

 5.6 



Grams. 

 6.67 

 6.60 

 6.00 

 5.86 

 5.70 

 5.63 

 4.72 

 6.14 

 6.65 



" The highest aud lowest figures giveu 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 tlie longer staples make stronger yarns. 

 The strength is in more direct ratio to the diameter. 



" The accurate measurement of the diameters of the twisted, ribbonlike cot- 

 ton fibers presents such difBculties and requires so much time that it is not 

 included in all tests." The average diameter for American Upland, measured 

 Avith an eyepiece micrometer, was 31.88 microns, maximum 34.8, and minimum 

 28.8; for Sea Island the average was 24.31, maximum 28.1, and minimum 21.75: 

 and for American-grown Egyptian the average was 23.3, maximum 28.1, and 

 minimum 18.4 microns. The pull necessary to detach the fiber from the seeds 

 in American Upland varieties ranges from 1.8S to 2.3 gm., and in Sea Island 

 from 1.75 to 1.95 gm. 



Long-fiber material constitutes two natural groups: (1) Soft fibers such as 

 bast fibers, which include flax, hemp, jute, and ramie; and (2) hard fibers, 

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

 hemp). The soft fibers vary greatly in thickness, and cling together so as to 

 make it practically impossible to select strands for comparison. 



For testing hard fibers, a machine having a capacity of 1 gm. to 90 kg. was 

 used, and the breaking strain of each sample was computed to an arbitrary 

 standard of a fiber weighing 1 gm. per meter of length. 



Weight and breaking strain of liard fibers. 



Kind of fiber. 



Weight 



per 

 meter. 



Average 



breaking 



strain 



per 

 strand. 



Breaking 



strain 



per 



gram 



meter. 



Abaci (Manila hemp), Musa textUis: 



Highest 



Lo west 



Average 



Henequen (Yucatan sisal), A gave fourcroydes 



Sisal (Hawaii and East Africa), A. sisalana 



Cantala (Manila maguey), A. cantala 



Phormium (New Zealand hemp), Phormium tenai 



Zapupe Vincent (A . lespinassei) •. . . 



Cabuya (from Costa Rica), Furcraea cabuya 



Grams. 



0. 04019 

 .06817 

 . 05470 

 . 05420 

 . 04370 

 . 03040 

 . 04670 

 .05120 

 . 04070 



Grams. 

 3,020 

 2,012 

 2,254 

 1,0S5 

 1,472 

 625 

 1,222 

 1,394 

 1,297 



Grams. 

 75, 143 

 29,521 

 45, 115 

 20, 021 

 32, 773 

 2,055 

 26, 159 

 27, 198 

 31,933 



