2. The scales lying close to the stem will have what effect on the surface of the fiber?

3. What effect will a smooth surface have on light?

4. What characteristic is given to mohair from the fact that the smooth surface reflects light?

5. From what animal is mohair obtained in greatest quant.i.ty?

6. Where is mohair being grown in the United States?

=Experiment 10--Cotton Fiber=

Apparatus: Microscope, foot-rule.

Materials: Tuft of cotton fibers, cotton ball, seeds.

Reference: _Textiles_, chapter ix, page 105.

_Directions_

1. Hold a tuft of cotton fibers tightly between the fingers and thumb of each hand and pull apart with a jerk. What is your judgment of the strength of the _staple_ (fiber)?

2. Loosen gently the fibers of one of the tufts you have pulled apart.

What is the feel of cotton? the appearance as you hold it to the light?

3. Detach several fibers one by one. How does the length compare with that of the wool and mohair? Measure and record the length of three fibers.

4. How do cotton fibers compare in fineness with wool fibers?

5. Compare the elasticity of cotton with that of wool.

6. Examine the cotton fibers under the microscope. Observe that the enlarged fiber looks like a twisted ribbon. When the fiber was growing it was cylindrical in shape. When ripe the plant drew back its life-giving fluid from the fiber and it collapsed and twisted like a corkscrew. The twist is peculiar to the cotton, being present in no other fiber. The twist makes the cotton fiber suitable for spinning, helping to hold the short fibers together.

7. Read of the cotton plant from _Textiles_, chapter ix.

8. The four chief cotton producing countries are the United States, Egypt, India, Brazil.

9. There are several cla.s.sifications of cotton. The most common are Sea Island (in the lead); Egyptian (a close second); Uplands (that of the United States, southern part); and Peruvian.

10. Uplands is the most common cotton of our South.

_Questions_

1. What characteristic causes the cotton fiber to be easily recognized under the microscope?

2. Why does the twist render the cotton fiber suitable for spinning?

3. What are the characteristics of the cotton fiber?

4. Why is cotton known as a vegetable fiber?

5. Name the chief cotton producing countries.

6. What are the most common cla.s.sifications of cotton?

7. What is the finest growth of cotton? (Sea Island commands at the present time $1.00 a lb., while Middling Uplands brings 15 cents.)

8. Where is cotton known as Upland Cotton grown?

=Experiment 11--Silk Fiber=

Apparatus: Tripod, alcohol lamp, small pan of water, lead pencil.

Material: Silk coc.o.o.n.

Reference: _Textiles_, chapter xvii, page 203.

_Directions_

1. Place the coc.o.o.n in a small pan of water. Apply heat to the pan until the water boils. The coc.o.o.n is placed in hot water to soften the glue which holds the fibers together.

2. Remove the outside loose fibers which cannot be reeled. This tangled silk on the outside of the coc.o.o.n is called _floss_.

3. Brush the finger over the coc.o.o.n to find the loose ends. Unwind carefully until you find a continuous end. Wind or _reel_ the silk fiber over a lead pencil.

4. The silk fiber is the most beautiful and perfect of all fibers.

5. Hold the coc.o.o.n to the light as you reel. How does the silk fiber compare in fineness with the wool and cotton fibers?

6. The silk fiber is from 1000 to 4000 feet long. Unlike the other fibers the silk fiber is already a thread.

7. How does light effect the silk fiber? When the gum is thoroughly washed off the silk takes on its l.u.s.ter which is its chief characteristic.

8. Break the fiber after you have reeled a small quant.i.ty. Notice how the fiber springs back. Extend and release again. What characteristic does this ill.u.s.trate?

9. Examine the silk fiber under the microscope. Notice that it is round and smooth and resembles a gla.s.s rod. It shows what appear to be two fibers united by the gum secreted at the same time that the fiber was formed. Describe the silk fiber as it appears under the microscope.

10. Silk is taken from the reel and twisted into a skein of raw silk and thus exported.

11. The manufacture in the United States begins with raw silk. It is handled here first by the _throwster_ who winds it from the skein and makes different varieties of thread.

_Questions_

1. Why is the silk coc.o.o.n first placed in hot water?

2. What is known as floss?