36 
BULLETIN 882, U. S. DEPARTMENT OF AGRICULTURE. 
that to a certain extent prevails during the flight of the airplane. 
These stresses were produced upon test samples 1 inch by 12 inches 
(8 inches between the jaws) by disengaging the weight pawl and 
loading the machine by hand at the rate of approximately 1 inch 
per minute. Stresses of 90, 80, and TO per cent of the original 
breaking strength of the cloth were produced and the sample allowed 
to remain in the machine until it broke from this continual load 
or until a reasonable time had passed in which it was certain that 
the cloth could be stressed indefinitely without breaking. The re- 
sults of these tests are shown below : 
Table 14. — Effect of continual stresses on 68 by 68 plain, weave fabrics made 
front fancy Pima if mch American Egyptian cotton. 
Sam- 
Fabric. 
Time of stressing at— 
8j. 
ceSKd.i 80 per cent load. 
90 per cent load. 
1 
H. m. s. \ H. m. s. 
18 1 42 30 
24 30 1 23 (Broke.) 
68 45 3 17 (Broke.) 
65 30 4 ! 3 (Broke. 
i 
H. m. s. 
10 (Broke.) 
2 
(Broke.) 
1 (Broke.) 
1 30 (Broke.) 
3 
4 
Special twist, mercerized in the piece and § 
1 The twist in the yarn of which this cloth is made was that obtained from using a twist multiple of 3.83 in 
the singles and 3. 63 in the ply. 
The above table is supplemented by figure 16, and in connection 
therewith the following conclusions are drawn : None of the fabrics 
were reliable when subjected to 90 per cent of the load in the manner 
described; for 80 per cent they were reliable for only a few hours; 
and for 70 per cent they were reliable for an indefinite length of 
time. These results show that the piece-mercerized sample was the 
best of the fabrics tested. 
Microscopic examination was made of the piece-mercerized fabric 
in comparison with the corresponding gray cloth to determine what 
effect mercerization had upon the construction of the cloth. This 
investigation showed that the number of ends per inch in the warp 
and filling remained constant. The diameter of the threads had been 
decreased, but despite this fact the dimensions of the interstices de- 
creased because of the flattening of the yarns in the cloth by the 
heavy roller of the mercerizing machine. The results of these tests 
are shown in Table 15. 
