88 



TEXTILE FIBRES. 



Sea Islands fibres are generally used. The length and the strength of 

 cotton fibres varies considerably, according to the situation and the 

 country in which they are grown. The strength of the cotton fibre 

 relative to its size is fairly great. As a rule, the thickest fibres, 

 though short in staple, are the strongest. 



East Indian fibres are not always well adapted for closely twisting 

 yarns. 



The great strength of East Indian cottons is mainly due to their having 



this property, but much 

 of it is lost when such 

 fibres are twisted with 

 those of American cotton 

 into a yarn. According 

 to the tests made by the 

 late Mr. Charles O'tfeil, 

 the breaking strain of two 

 principal growths of fibres 

 is as follows : Sea Island, 

 83*9 grains ; Surat cotton, 

 163'7 grains. 



In the spiral structure 

 of cotton fibre the margins 

 are more thickened than 

 the central portions. Ripe 

 fibres are more twisted 

 than unripe ones. This 

 is probably due to the 

 deposition of material on 

 the inside of the cell-wall 

 taking place on two sides 

 Fig. 62.-Brown Egyptian seed cotton. alternately, so that when 



the protoplasmic elements are withdrawn from the wall, there is a collapse 

 of certain parts of the cellulose, causing the fibre to appear spiral or 

 twisted. The shape of the fibre, as seen in transverse section, is oblong, 

 half-moon-shaped, triangular or dumbbell-shaped, the last being that most 

 characteristic of a fully ripe fibre, and the circular that of an unripe 

 fibre. In the ripe fibre a fistulose structure is apparent, but in the 

 unripe fibre this is seldom evident. 



Crops. Cotton fibres of the new season's crop are sometimes bloomy 

 staples, indicating that there is some deception in the strength of staple, 

 and that it is slape and weak, although the lustre is highly effective. 

 Some of the fibres will fail to take the dye, so that in indigo and alizarine- 



