arn in Cloth=

Apparatus: Scales, ruler.
Material: Samples of fabrics.
Reference: _Textiles_, pages 144-146.

The United States Government imposes a tax on certain imported fabrics
and yarn. In the case of cotton, the rates of duty are to be
ascertained according to the average number of the yarns in the
condition in which it is imported.

The length of the yarn is to be counted as equal to the distance
covered by it in the cloth, all clipped threads to be measured as if
continuous and all ply yarns to be separated into singles and the
count taken of the total singles; any excessive sizing is to be
removed by boiling or other suitable processes. The number of the yarn
is the English number of 840 yd. to a lb. for a No. 1 yarn.

The average number of yarn may be found without unraveling the fabric,
and is the quotient of the total thread length, by the weight in the
proportion of 840 yd. of yarn equaling 8-1/3 grains, which is
equivalent to a No. 1 yarn.

The following simple formula may be used:

Multiply the count of threads per square inch by the number of square
inches in the sample used, this product to be multiplied by 100; then
divide the product thus obtained by the weight of the sample in grains
multiplied by 432. The quotient will give the number of the yarn.

For example, take a sample of cotton cloth 4 in. square, which equals
16 sq. in., having 28 warp and 28 woof threads, a total of 56 threads
to the square inch, and weighing 8.6 grains. The formula applied would
be as follows:

(56 x 16 x 100) / (8.6 x 432) = 24, the number of the yarn.

The formula may be further simplified by weighing a square yard of the
cloth and dividing the number of threads per square inch by 1/300 of
the weight per square yard in grains.

Find the number of yarn in several cotton fabrics.

=Experiment 61--Study of Fabrics=

A great deal of time should be devoted to the study of standard
fabrics so that pupils may be able to recognize them by inspection and
know how to test them for adulterants.

This may be done by having the pupils study the fabrics one by one,
placing a sample of each in a note-book. Underneath the sample should
be written the use of the fabric, the width, the different grades,
with prices, wearing qualities, and how the fabric is made. In
connection with this work special effort should be made to develop a
textile vocabulary so as to be able to discriminate between the
differe