2024年4月6日发(作者：)

Lesson1

We can read of things that happened 5,000 years ago in the Near East, where

people first learned to write. But there are some parts of the world where even

now people cannot write. The only way that they can preserve their history is to

recount it as sagas--legends handed down from one generation of story-tellers to

another. These legends are useful because they can tell us something about

migrations of people who lived long ago, but none could write down what they did.

Anthropologists wondered where the remote ancestors of the Polynesian peoples

now living in the Pacific Islands came from. The sagas of these people explain that

some of them came from Indonesia about 2,000 years ago.

But the first people who were like ourselves lived so long ago that even their

sagas, if they had any, are forgotten. So archaeologists have neither history nor

legends to help them to find out where the first 'modern men' came from.

Fortunately, however, ancient men made tools of stone, especially flint,

because this is easier to shape than other kinds. They may also have used wood

and skins, but these have rotted away. Stone does not decay, and so the tools of

long ago have remained when even the bones of the men who made them have

disappeared without trace.

Lesson2

Why, you may wonder, should spiders be our friends ? Because they destroy so

many insects, and insects include some of the greatest enemies of the human race.

Insects would make it impossible for us to live in the world; they would devour all

our crops and kill our flocks and herds, if it were not for the protection we get from

insect-eating animals. We owe a lot to the birds and beasts who eat insects but all

of them put together kill only a fraction of the number destroyed by spiders.

Moreover, unlike some of the other insect eaters, spiders never do the least harm

to us or our belongings.

Spiders are not insects, as many people think, nor even nearly related to them.

One can tell the difference almost at a glance for a spider always has eight legs

and an insect never more than six.

How many spiders are engaged in this work on our behalf ? One authority on

spiders made a census of the spiders in a grass field in the south of England, and

he estimated that there were more than 2,250,000 in one acre, that is something

like 6,000,000 spiders of different kinds on a football pitch. Spiders are busy for at

least half the year in killing insects. It is impossible to make more than the wildest

guess at how many they kill, but they are hungry creatures, not content with only

three meals a day. It has been estimated that the weight of all the insects

destroyed by spiders in Britain in one year would be greater than the total weight

of all the human beings in the country.

Lesson3

Modern alpinists try to climb mountains by a route which will give them good