英文科學讀本 第三冊·Lesson 04 A Feather

Lesson 04 A Feather

Where have you been, Fred? asked Will. "We have hunted everywhere for you."

I've been in the fowls' house, said Fred, "to find a few feathers. Look what a fine lot I've got. They will do well, won't they?"

Oh, I know, said Will. "You are thinking about our lesson. Yes, they will be just the thing. Where's Norah?"

In a few minutes the three were seated at the table ready for a chat, and Fred handed some of the quill feathers round.

Now, a glance at one of these feathers, he said, "will tell us that it consists of two parts. There is the long stem, which runs from the root to the very tip of the feather, and on either side of this is the blade or web."

Let us examine the central stem first. The lower half of it near the root seems to be quite different from the upper half. Try and cut it across with your knife, Will. Will tried, but he found it no easy task to cut through this part of the stem, for it was like strong, tough horn. However, he did cut it across at last, and then they saw that it was really a round hollow tube.

Teacher calls this lower part of the stem the quill, said Fred. " It is thin, hollow, and extremely light, but it is very tough, strong, and elastic, and will bear a great deal of rough usage. The lower end of it forms the root, which holds it in the skin of the bird."

Now let us look at the other part of the stem. It is called the shaft. Suppose you strip your feather and then examine it. What can you say about it?

The quill of the feather is round, said Norah, "but this part has four sides. The upper and under sides are smooth, like the surface of the quill, the other two sides are rough. It was from these edges of the shaft that we tore off the web just now. I can see, too, that the shaft becomes smaller and smaller towards the tip."

Quite right, said Fred. "Now we will go a step farther. Watch, while I cut through the shaft as we did through the quill just now. This part of the stem, you see, is not hollow like the quill. It is filled with a loose, white, tough substance—the pith."

We have done with the quill and the shaft now, he continued. "I want you to turn your attention to the other part of the feather, which teacher calls the web."

If you examine this web you will see that it is made of a great many long, narrow, thin blades— the barbs. These spring from the shaft, and are arranged with their two flat sides close together.

Pluck one or two of them. You can see that the edges of the barbs are provided with a great number of very small blades—the barbules. Barbule means a little barb.

These barbules are really little hooks. They interlock themselves one in the other, and so hold the barbs of the web close together.

Look, while I run my finger along the feather the wrong way. You see the little hooks are pulled apart, and the barbs themselves are separated from each other.

Teacher showed us that the barbs always point towards the tip of the feather, and away from the quill; and, in addition to that, every feather on the bird's body points backwards.

This is very important. As the bird moves through the air the feathers are pressed closer and closer to its body. This helps the bird in its flight, and, at the same time, keeps it warm.

SUMMARY

A feather consists of a stem and a web. The stem has a hollow quill, and a shaft filled with light pith. The web consists of barbs; the edges of the barbs are held together by the barbules. All the birds' feathers point backwards.