16 BULLETIN 121, U. S. DEPARTMENT OF AGEICULTUEE. 



After the cotton has reached the mill it is still possible to get 

 varying results from the same bale by running the beaters too fast, 

 thus breaking the fibers, by feeding too heavily, or by operating with 

 improper adjustments of beater grids, or by allowing too strong an 

 air current on the pickers. 



On the card it is possible to get a wide variation in results, even 

 when the machine is supposed to be adjusted accurately. The reason 

 for this is that the most important settings or adjustments are made 

 anywhere between five and fifteen one-thousandths of an inch. A 

 difference of one or two thousandths will measurably affect the per 

 cent of waste. It is therefore apparent that only the most painstak- 

 ing care can obviate these possibilities of error. Again, if the speed 

 of certain parts of the card is varied, or if a heavier lap is fed. or 

 if the grinding of the steel wire clothing of the cylinder, doffer. or 

 revolving flats is neglected, or if the stripping of these is too infre- 

 quent, a varying amount of waste will result. 



At the comber a number of conditions may cause a variation in 

 the amount of waste. Among these are differences in speed, in the 

 angle of the top comb, in the distance between the nippers and the 

 detaching rolls, in the weight of the lap, in the rate of feed, the 

 timing of the parts, etc. If any of these factors are changed, even 

 in a slight degree, a different result is obtained. The temperature 

 and humidity also affect the results of such tests. 



Items enough have been enumerated to show the possibility of 

 error in tests of this nature. However, as all of these tests were 

 made on the same machines, and all except the Delta, at the same 

 time, and without the slightest mechanical change, the results ob- 

 taned are strictly comparable as to five samples and very closely 

 comparable as between these and the Delta. 



TESTS OF BREAKING STRENGTH. 



Table X shows the breaking strength in pounds per skein of the 

 carded and combed yarns. All varieties were spun into 50s yarn, and 

 the twist per inch was calculated as follows: The standard twist 

 factor for filling yarns being 3.25, this factor, multiplied by the 

 square root of the counts (50s) gives the twist per inch thus: V50= 

 7.07; 7.07X3.25=22.97 turns per inch. 



In preparing the yarn for these breaking strength tests it is tfi2 

 custom of the trade to reel off a skein containing 120 yards. The 

 reel is 54 inches in circumference, and when the skein is attached to 

 the testing machine it is an endless length of yarn. This skein is 

 hung upon two hooks and when the tester is started these hooks begin 

 to draw slowly apart. The strength of the skein is registered on a 

 dial. 



