Testing Yarns.
In addition to wrapping warp yarn to ascertain actual counts, it is frequently tested as to strength; the lea from the reel is placed between two hooks on a testing machine, and by a wheel worm and screw the lower hook is moved downwards, increasing the tension on the yarn. By an index finger this tension is indicated on a face plate, and when the lea is broken the finger stops at the highest weight or strain that the yarn has stood. Below is a table, which will give a general idea of the comparative strength of mule twists, having, for the American cotton, the standard turns in—i.e., square root of counts multiplied by 3-3/4.
| 20’s | American Cotton | = 80lb. |
| 30’s | American Cotton | = 54lb. |
| 40’s { | American Cotton | = 40lb. |
| Egyptian Cotton | = 50lb. | |
| 50’s { | American Cotton | = 28lb. |
| Egyptian Cotton | = 37lb. | |
| 60’s | Egyptian Cotton | = 30lb. |
| 70’s | Egyptian Cotton | = 26lb. |
In yarn the diameters of the threads do not vary inversely as the counts, but inversely as the square root of the counts. Thus, 16’s is not four times as thick as 64’s, but twice as thick, the square roots being four and eight respectively.