108 THE DEVELOPMENT OF RAW COTTON 



We now turn to the results of handing the ginned lint 



from the dated flowers to an expert grader, in order to 



assess their " strength." The manner in 



Grading and W j 1 j c j 1 tnis was done nas been described 



Hair Strength. 



in the Appendix, and it may be taken for 



granted that the grader had no guide whatever as to 

 the relation between the various samples, nor any oppor- 

 tunity of revising his judgments. His results can also 

 be arranged in a curve, and smoothed to five-day means, 

 and compared directly with the other curves. 



When treated in this way it at once becomes apparent 

 that grader's " strength" and "breaking strain" are 

 utterly disconnected, and have nothing whatever to do 

 with one another. This is a practical result of the first 

 importance. 



The most striking example of this is at the end of the 

 curve (Fig. 21), where the breaking strain is falling rapidly 

 to zero, but the grading remains up at SS on the scale. 

 Comparing this with the notes given in the previous 

 section as to the behaviour of 77 G. and 310 N., it becomes 

 possible to see what Strength, as determined by hand- 

 pulling, really means. The grader takes a tuft of lint to 

 test, keeping to a uniform size of tuft ; if the hairs are but 

 slightly thickened, and consequently of low breaking 

 strain, he takes more of them; while if they are heavily 

 thickened, coarse, and of considerable strength individu- 

 ally in consequence, he includes fewer to obtain a tuft of 

 the same size. 



It is pointed out in the Appendix on p. 191 that " im- 

 pact testing " of a bunch of fibres gives a result which is 



