6 
BULLETIN" 591, U. S. DEPARTMENT OF AGRICULTURE. 
graph were taken from Table II and placed in this position for con- 
venient reference. The close relationship between the cotton from 
the two sections of the cotton belt and the relationship between the 
grade and the percentage of waste are apparent. 
It .should be borne in mind that the greater part of the cotton 
taken out as waste has a commercial value, since it is used in various 
branches of the waste industry. 
TENSILE-STRENGTH COMPARISONS. 
In order to test the yarn produced from each grade of cotton under 
uniform conditions, tensile-strength tests were conducted in the lab- 
oratory of the Bureau of Markets, United States Department of 
Agriculture, at Washington, D. C. Cotton is hygroscopic, and any 
change in atmospheric moisture affects the tensile strength of the 
material. The laboratory is equipped with humidifiers which are 
regulated by an automatic control within approximately i per cent. 
Skeins of 120 yards each were reeled off the bobbins of yarn made 
from the different grades of cotton and placed separately on racks 
constructed for this purpose. After a sufficient number of skeins 
had been reeled off to give positive results x they were allowed to 
condition in the testing room, having a temperature of 70° F. and a 
relative humidity of 65 per cent. Subsequently they were taken 
from the racks one at a time in rotation and broken with a power 
yarn tester, the downward stroke of the traverse moving at the rate 
of approximately 12 inches per minute. 
Table III gives the result of the tensile-strength tests of 22's warp 
yarns made from five grades of eastern upland and five grades of 
western upland cotton. 
Table III. — Comparative tensile strength o/22 y s yarns in -pounds per skein of 120 yards 
{mill tests). 
Twist » 
Eastern upland. 
Western upland. 
constant. 
M.F. 
G. M. 
M. L.M. 
G. 0. 
Av. 
M. F. 
G.M. 
> 
M. 
L.M. 
G. O. 
Av. 
4 20 
75.9 
75.7 
74.1 
72.5 
76.0 
76.4 
75.8 
69.8 
75.2 
74.4 
70.5 
69.8 
72.3 
73.1 
71.0 
69.6 
70.4 
67.5 
66.4 
67.6 
74.0 
73.4 
71.6 
69.9 
84.1 
86.3 
82.4 
82. 7 
85.7 
82.1 
79.0 
7S.9 
83.7 
82.3 
79.1 
78.5 
72.2 
73-3 
69.7 
69.1 
76.6 
75.9 
75.1 
71.9 
80.5 
4.54 
4 74 
80.0 
77.1 
4 95 
76.2 
Average 
74.6 
74.5 
72.5 ; 71.5 
68.0 
72.2 
83.9 
81.4 
80.9 [ 71.1 
1 
74.9 
78.5 
1 See footnote, p. 17. 
Table III shows that the grade of the cotton does not always 
govern the tensile strength of the yarn. 
During the month of June, 1915, within which this cotton was 
purchased, it was not possible to secure different grades of cotton 
1 By taking subtotals and averaging the tensile strength it was found that 24 skeins usually were sufficient. 
