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cannot be reproduced, for reasons of cost, in the conventional way. It is a technique that makes possible the production of unique copies or very limited editions at a cost far lower than is possible with other techniques of reproduction.

Microphotographic reproduction provides exact facsimiles of original records. Since the technique is a cheaper process of reproduction than printing, many documents are likely to be in­ cluded in a microfilm publication that would ordinarily be re­ jected for publication in the more expensive printed form.

Documents may be reproduced in an abstract form in calendars.

As the work on calendars progressed, they became more and more complete, eventually providing so much information on particular documents that reference to the originals was un­ necessary. When calendars serve as substitutes for the originals because of the abundance of information contained in them, they may be considered as a form of documentary publication; normally they are considered as a form of finding aid.

♦ Make up important questions on the textyou havejust read and letyour groupmates answer them.

Text 50

Engineering Marvels o f the Greeks and Romans

Modem engineers owe a large debt to the great civiliza­ tions of Greece and Rome. Engineers and architects have hatiled the Parthenon and other great Greek public buildings as among the most architecturally perfect of man's creations. Yet there is something odd, and at the same time very significant, about all Greek buildings. From the humblest home to the larg­

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est public auditorium, they all rose from a simple rectangle. The walls were supported by posts and beams, a method of con­ struction the Greeks had learned from the Egyptians and other older civilizations. The slanting (pitched) roofs were formed by a ridgepole and rafters, as many of our houses are today. There were porches, supported by columns which sometimes ran around all four sides of the rectangle. In the larger buildings, in­ terior columns helped support the weight of the roof.

This was the simple, fixed rectangular form. Yet no two Greek buildings were exactly alike, because the Greeks were artists as well as engineers. You can convince yourself of this by trying to make a drawing from the picture of the Parthenon included here. You will find that the beauty of the building depends almost entirely on the proportions of the various parts. Without these very slight but skillful changes in proportion, Greek buildings would have had no more beautiful dimensions than a modern one-car garage which starts from the same rectangular plan.

Let us take, for example, the Parthenon. This famous Greek temple is, basically, a rectangle 100 feet wide and 228 feet long. It has 46 Doric columns, each 34 feet high. To the eye, it may seem that these columns are composed of perfectly straight vertical lines. Actually, however, they curve. They measure 6 feet 3 inches at the base, widen slightly as they rise, and then gradually taper to 4 feet 10 inches in width at the top. You will notice that these columns have grooves, called flutings. These flutings are wider at the bottom of the columns, narrowing as they reach the top. But they do not vary in depth. Such subtle refinements as these are responsible for the fine shadow effects produced in Greek Buildings.

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Even the horizontal lines of the Parthenon and other great Greek structures, are not truly horizontal. The steps leading up to the temple, for instance, are not level, but rise-toward the centre in a gentle arc. The Greeks did this because they knew so much about lines and planes and the optical illusions they can create. They knew that if the Parthenon steps were hori­ zontal, they would appear to sag in the center because of the extreme breadth of the stairs.

The Greeks made great use of the simple machines in their engineering. They cut the outline of a building block into a wall of marble and then split it away by driving wooden wedges into the cut and the wetting the wedges. The pressure of the water-swollen wedges was enough to split off the build­ ing stone along the cuts. The Greeks did not smooth their blocks at the quarry as the ancient Egyptians had done - in­ stead the Greeks left knobs on the stone under which levers could be placed to pry the stones out of the quarry.

Sometimes the building stones were hauled to the building site in ox-drawn carts. At other times the Greeks put the blocks on wooden cradles, under which they placed long rollers to serve as wheels. Still another method was to enclose the block in a round drum of wood and roll the whole thing to the job. Derricks and compound pulleys were used to handle the blocks of stone at the site of the building project.

Few people realize, when looking at pictures of the beauti­ ful stone temples of the Greeks, that their building engineers used a great deal of iron in their work. Where the Egyptians had used stones so massive that they held together by their own weight, the Greeks cut much smaller stones and clamped them together with bars of iron. These bars were bent at right angles

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at each end, and these ends went into holes drilled into the stones. There were grooves cut into the stone between these holes so that the bars would be flush with the face of the stone. Often foundations, crossbeams over doorways, and rather beams were reinforced with iron bars to increase safety. The iron clamps and the iron-bar reinforcements were sealed in with hot lead. The iron was probably treated with allow to make it rust-resistant, but today most of the iron in the ancient Greek ruins has rusted away entirely.

Thus the Greeks seem to have the first engineers to realize that while stone is strong and durable, it does not have the tensile strength (stretching strength) of iron. Tensile strength is measured by the amount ofweight necessary to break a given material.

A class of master workmen of great engineering skill ap­ peared among the Greeks. The most skilled of these were called architectrons, and one of these was in charge of every building project. They directed the workmen, working from specifications cut on a stone tablet which would correspond to the blueprints of the modem engineers. On this tablet the materials to be used, sizes of stones, dimensions of the building and its parts, location and number of windows, doors, steps, and other details were cut.

The Greeks were among the first to plan cities. The cities built during the later period of their civilization had wide main avenues and cross streets, forming rectangular blocks in which were built the public buildings, temples, theatres, homes, ath­ letic fields, monuments and parks.

The streets were paved, and the water supply for each block or square came from a central fountain. These street fountains were fed from springs high in the mountains. Ditches and pipes carried the water to a reservoir near the city, and

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more clay pipes led from the reservoir to the street fountains. In the finer homes of the rich or the influential Greek citizens, water pipes supplied bathrooms and water taps.

The bathroom of a rich man's home in ancient Greece was almost as fine as that of the average American today. Greek ruins have been found which contain built-in tubs, with an overhead spout connected to spring-fed pipes from the hills. There was even a tile drain at the bottom of the tub.

Yet, although their streets were paved and there were a few short roads leading to quarries and wharves, the Greeks were not great road builders.

Curiously, the Greek world possessed skills and ideas which were almost wholly neglected by the Greek engineers themselves. Those gifts included geometry, which Euclid or­ ganized into a body of mathematics, and the many scientific experiments and theories by Archimedes and other Greek philosophers. They may be said to have laid the foundations for modem science, upon which the modem engineer depends so heavily for advancements in his field. The Greek engi­ neers, however, made little use of these things. Their engi­ neering feats were mainly improvements on techniques they had learned from the Egyptians and other earlier peoples, or which they had learned from experience, rather than from scientific theory or experiment.

For example, while the Greek workmen were building their classic temples with oxcarts, levers, and pulleys, a Greek scholar named Hero was trying to develop a steam turbine. Other Greeks were experimenting with water clocks, force pumps and similar mechanical engineering.

The Greeks made only a small contribution to marine engi­ neering. Their ships were much like those of the Egyptians, with square sails and with little ability to sail against the wind.

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They did, however, make their ships broader in the beam (wider) in order that they might safely carry much larger car­ goes than the narrow Egyptian ships.

In military engineering, however, the Greeks made some notable advances in weapons, the first since the spear and bow and arrow. Most of these mechanical weapons were invented by Archimedes, whom we usually think of as a mathematician and scientist. It was he who established the laws o f . the lever and other simple machines, although men had been using such machines without knowing their laws for thousands of years. It was Archimedes, too, who established other principles of physics which engineers use in their work today. One of these was the discovery that an object placed in water displaces an amount of water equal to the volume of the object, and the ob­ ject "loses" in weight by the amount of the water displaced.

But Archimedes, who studied at the famous Egyptian school of mathematics in Alexandria, was also an inventor and practical engineer. His war machines were responsible for many Greek victories in battle. One of these was a battering ram - a huge beam mounted on movable arms so that it could be swung back and forth inside a wheeled frame. A few men working the battering ram could run the frame to the side of a wall and batter an opening through the stones.

Another weapon developed by Archimedes was the cata­ pult. This was a springy lever which was pulled back and loaded with a huge stone, and then released to send the stone flying hundreds of feet.

You can make a catapult of your own that will be a lot of fun for target practice or for use in mock battles with your friends. First, select the springiest tree branch or strip of wood

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you can find. Mount this on a sturdy wooden base at an angle, as shown in the drawing. Next, take a tin can, and nail or screw the can to the spring arm of your catapult. In winter, you can load your catapult with snowballs. In summer it would be safer to use cheap rubber balls for ammunition - rocks fired from your catapult can be dangerous. To fire, you simply pull the spring arm down as far as you can and let go.

♦ Make up a plan. Use some steps to organize sentence out­

line.

1.Read the text very carefully to understand its plot.

2.Divide it into logical parts.

3.Write down the main ideas of these parts. They will serve as main headings. Number them with Roman numerals.

4.Fill in the supporting details for each main heading if necessary. Identify these subheadings with capital letters. In­ dent them beneath the Roman numeral headings.

5.Express the main ideas and supporting details in com­ plete sentences.

6.Review your outline. Be sure that each heading is care­ fully worded and concise.

Text 51

Sleep

We all know that the normal daily cycle of activity is of some 7-8 hours' sleep alternating with some 16-17 hours' wake­ fulness and that, broadly speaking, the sleep normally coin­ cides with the hours of darkness. Our present concern is with how easily and to what extent this cycle can be modified.

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SUPPLEMENT

♦ Translate.

1.Только что получена ценная информация.

2.Наша лаборатория будет переоборудована.

3.Разработаны реальные проекты.

4.Выдвинуты полезные идеи.

5.Все старое оборудование будет демонтировано.

6.Новое надежное оборудование уже разработано.

7.Скоро будут получены ценные результаты.

8.Экономические проблемы, с которыми столкнулись все стороны, очень сложны.

9.Ущерб окружающей среде, наблюдаемый нами, но­ сит глобальный характер.

10.Данные, полученные в ходе исследований, не отли­ чаются от прежних результатов.

11.Ученые, работающие в любой области науки, не должны забывать о своей ответственности.

12.Полагаем, что эта научная проблема будет решена.

13.Следует понять, что математика - абстрактная наука.

14.Среди задач такого класса эта задача самая сложная.

15.В течение почти двух столетий среди самых вы­ дающихся нерешенных задач были задачи простых чисел.

16.Теория, которая будет проверяться в этих экспери­ ментах, вполне убедительна.

17.Данные, которые необходимо получить в ходе экс­ периментов, будут представлены в таблицах.

18.Подход к проблеме, которой мы будем придержи­ ваться, значительно отличается от предыдущих.

19.Мы не можем не попытаться дать определение этим понятиям.

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