2024年5月2日发(作者：找不到打印机怎么办)

psychology托福听力原文

TPO2 Lecture 2 Psychology

Narrator : Listen to part of a lecture from a Botany class.

Professor : Hi, everyone. Good to see you all today. Actually, I

expected the population to be a lot lower today. It typically runs

between 50 and 60 percent on the day the research paper is due.

Um, I was hoping to have your exams back today, but, uh, the

situation was that I went away for the weekend, and I was supposed

to get in yesterday at five, and I expected to fully complete all the

exams by midnight or so, which is the time that I usually go to bed,

but my flight was delayed, and I ended up not getting in until one

o'clock in the morning. Anyway, I'll do my best to have them finished

by the next time we meet.

OK. In the last class, we started talking about useful plant fibers.

In particular, we talked about cotton fibers, which we said were very

useful, not only in the textile industry, but also in the chemical

industry, and in the production of many products, such as plastics,

paper, explosives, and so on. Today we'll continue talking about

useful fibers, and we'll begin with a fiber that's commonly known as

Manila hemp. Now, for some strange reason, many people believe

that Manila hemp is a hemp plant.

But Manila hemp is not really hemp. It's actually a member of

the banana family- it even bears little banana-shaped fruits. The

Manila part of the name makes sense, because Manila hemp is

produced chiefly in the Philippine Islands and, of course, the capital

city of the Philippines is Manila. Now, as fibers go, Manila hemp

fibers are very long. They can easily be several feet in length and

they're also very strong, very flexible. They have one more

characteristic that's very important, and that is that they are

exceptionally resistant to salt water.

And this combination of characteristics-long, strong, flexible,

resistant to salt water-makes Manila hemp a great material for ropes,

especially for ropes that are gonna be used on ocean-going ships.

In fact, by the early 1940's, even though steel cables were available,

most ships in the United States Navy were not moored with steel

cables; they were moored with Manila hemp ropes. Now, why was

that?

Well, the main reason was that steel cables degrade very, very

quickly in contact with salt water. If you've ever been to San

Francisco, you know that the Golden Gate Bridge is red. And it's red

because of the zinc paint that goes on those stainless steel cables.

That, if they start at one end of the bridge and they work to the

other end, by the time they finish, it's already time to go back and

start painting the beginning of the bridge again, because the bridge

was built with steel cables, and steel cables can't take the salt air

unless they're treated repeatedly with a zinc-based paint. On the

other hand, plant products like Manila hemp, you can drag through

the ocean for weeks on end. If you wanna tie your anchor to it and

drop it right into the ocean, that's no problem, because plant fibers

can stand up for months, even years, in direct contact with salt water.

OK. So how do you take plant fibers that individually you could

break with your hands and turn them into a rope that's strong

enough to moor a ship that weighs thousands of tons? Well, what

you do is you extract these long fibers from the Manila hemp plant,

and then you take several of these fibers, and you group them into

a bundle, because by grouping the fibers you greatly increase their

breaking strength-that bundle of fibers is much stronger than any

of the individual fibers that compose it. And then you take that

bundle of fibers and you twist it a little bit, because by twisting it,

you increase its breaking strength even more. And then you take

several of these little bundles, and you group and twist them into

bigger bundles, which you then group and twist into even bigger

bundles, and so on, until eventually, you end up with a very, very

strong rope.