范文一
Irrigation, the artificial watering of land for agriculture, uses water from a number of sources: direct rainfall, direct stream flow, water stored in lakes and reservoirs, high-quality groundwater, brackish surface water, and even seawater. Water for irrigation is diverted from rivers and lakes or pumped underground. Different crops have different irrigation requirements, so there are many forms of irrigation and types of irrigation technology.
Various methods of surface irrigation deliver water to a field directly from a canal, well, or ditch. The surface technique of flooding large fields is widely used because of low capital costs and long tradition. Furrow irrigation, practiced since ancient times, involves digging numerous U-or V-shaped open furrows through irrigated land and introducing water into them from a channel at the top of a field. As with other surface techniques, water collects into ponds on the field. In surface-pipe irrigation, the water is piped to the field and distributed via sprinklers or smaller pipes.
Border irrigation is a type of surface irrigation that involves flooding land in long parallel strips separated by earth banks built lengthwise in the direction of the slope of the land. Water flows from the highest point in the field to the lowest. Basin irrigation is similar to border irrigation but includes earth banks constructed crosswise to those used for border irrigation, dividing a field into a series of basins that can be separately irrigated.
范文二
Listening tape script
n The great library of Alexandria no longer exists, but it’s not known for sure when the library was destroyed. There’s actually considerable debate among historians about who destroyed the library and when. One culprit who has traditionally been accused of destroying the library at Alexandria is Julius Caesar. It’s true that Julius Caesar led an invasion of Alexandria in 48-47 B.C and that, at that time, his forces set the fleet of ships sitting in the Alexandria harbor on fire. Some historians believe that this fire in the harbor that was set by Caesar’s forces, spread into the city of Alexandria and burned the library down, but this belief is no longer widely held today.
n The main reason that the theory that Julius Caesar destroyed the library at Alexandria isn’t widely believed is that there are numerous references to the library in works written long after Caesar’s death.
n The conclusion that seems to be most accepted today is that the library at Alexandria existed, at least in part, until the late fourth century, centuries after the death of Julius Caesar, so it could not have been completely destroyed by Caesar.
n At that time, at the end of the fourth century, there was a large movement to destroy pagan temples and libraries. It seems likely that whatever remained of the library of Alexandria was destroyed at this time.
范文三
Reading material
n The library at Alexandria was said to have been a marvel, the greatest collection of scholarship in the ancient world. It was founded by Ptolemy I, the general that Alexander the Great installed as ruler of the city named after himself. It was Ptolemy’s son, Ptolemy II Philadelphus, who had the vision of expanding the library to make it the largest collection imaginable.
n Under Ptolemy II and those who followed, the library was expanded tremendously. Ptolemy II’s vision was to create a library with every Greek work ever written as well as with as many works from other parts of the Western world as could be gathered together.
n The number of volumen, or scrolls, in the library has been estimated at anywhere between 300,000 and 700,000.
n A huge number of people were employed in preparing scrolls for the library, in as much as each scroll to enter the library had to be copied by hand. Manuscripts were bought or borrowed or taken from all over the Western world to be copied and placed in the library (although it was rather common to copy an original manuscript and then return the copy to the owner and keep the original for the library).
n Ptolemy II often asked for manuscripts from foreign powers in return for traded goods, and manuscripts were often demanded from citizens to pay debts to the government.
n In addition, any time that manuscripts were found on trading ships in the port at Alexandria, the manuscripts were taken and copied and added to the library. It was in these ways that so many manuscripts were collected in the library at Alexandria.
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