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Early bridges had to be built out of material close at hand. In tropical jungles suspension bridges were made of long bamboo poles. In the places

where there were many forests, wood was used. In northern areas pier bridges were built out of stone. In the Middle Ages people constructed wooden beam type bridges. They were usually built on stone piers or wooden piles. Later there appeared concrete and metal bridges.

Nowadays some people ari experimenting with different unusual materials. One of them is paper. Everyone associates paper with weakness. But paper-makers consider it to be a very strong material. In order to prove it paper-makers built a paper bridge across a narrow canyon in Nevada.

The bridge covered a span of 32 ft. The designers calculated that it could safely span 80 ft The structure is ten ft.wide and four ft high It took the engineers only two months to design, test and construct the bridge.

For testing the engineers chose a truck which weighed 12,000 lb. This truck drove quite safely across the paper bridge. The engineers are sure that the bridge can take six times the truck load of 12,000 lbs. (pounds).

The bridge itself weighs 9,000 lbs. (pounds). So the structure was light enough to be laid into place by helicopter.

UNIT 12 Key to Ex. 8

7. elevation

8. building

9. preliminary

10. embankment

11. manufacture

AIJDIAL PRACTICE ] 1» Telephone Answering Machine

This is Markony'$(Цгшу\agency, 14 Oxford Street.We're sorry the agency is closed at the monflht From Monday to Thursday office hours are between nine-thirty a mi tnd m thirty p.m. Friday office hours are from ten-thirty a m to four p m If you have an urgent message please speak after the tone, or call ua |Ain during office hours.

Our telephone nulbl U 6725871. Thank you for your call.

Personal Cc We use them to present data with computer games Do you know a truly modern < The dimension X22 is that it comM I a great machinc other machines, printer. There ai

X22 Computer

Tpiy P( s are a common feature of our life, iftl or prepare a text; we turn to them to Hlpln or diagrams, or just to relax playing

>Ut tlir fantasy X22? The Fantasy X22 is |llt hui a disk drive and a colour monitor. Ш inches The main feature of the Fantasy ^ftr word processing. The Fantasy X22 is advantages. It is compatible with most amputcr is $ 800 which includes the ■available for it. They are listed in the

catalogue. It has two floppy disk drives: for 3.5 and 5.1/4 inch disks. A CD ROM is also available if necessary. The computer has a keyboard of 101 keys. The hard disk has 840 megabites of memory space. The computer has 640K. of base memory and 8 MG of extended memory.

UNIT 13

Key to Ex. 6

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