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考研背诵50篇——30 The origin of Refrigerators
By the mid-nineteenth century, the term icebox had entered the American language, but ice was still only beginning to affect the diet of ordinary citizens in the United States . The ice trade grew with the growth of cities. Ice was used in hotels, ta
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考研背诵50篇——31 British Columbia28.Changing Roles of Public Education
British Columbia is the third largest Canadian provinces, both in area and population. It is nearly 1.5 times as large as Texas , and extends 800 miles( 1,280km ) north from the United States border. It includes Canada s entire west coast and the isl
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考研背诵50篇——32 Botany
Botany, the study of plants, occupies a peculiar position in the history of human knowledge. For many thousands of years it was the one field of awareness about which humans had anything more than the vaguest of insights. It is impossible to know tod
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考研背诵50篇——33 Plankton
Scattered through the seas of the world are billions of tons of small plants and animals called plankton. Most of these plants and animals are too small for the human eye to see. They drift about lazily with the currents, providing a basic food for m
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考研背诵50篇——34 Raising Oysters
In the oysters were raised in much the same way as dirt farmers raised tomatoes- by transplanting them. First, farmers selected the oyster bed, cleared the bottom of old shells and other debris, then scattered clean shells about. Next, they planted f
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考研背诵50篇——35.Oil Refining
An important new industry, oil refining, grew after the Civil war. Crude oil, or petroleum a dark, thick ooze from the earth had been known for hundreds of years, but little use had ever been made of it. In the 1850 s Samuel M. Kier, a manufacturer i
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考研背诵50篇——36.Plate Tectonics and Sea-floor Spreading
The theory of plate tectonics describes the motions of the lithosphere, the comparatively rigid outer layer of the Earth that includes all the crust and part of the underlying mantle. The lithosphere(n.[ 地 ] 岩石圈 )is divided into a few dozen p
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考研背诵50篇——37 Icebergs
Icebergs are among natures most spectacular creations, and yet most people have never seen one. A vague air of mystery envelops them. They come into being ----- somewhere ------in faraway, frigid waters, amid thunderous noise and splashing turbulence
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考研背诵50篇——38 Topaz
Topaz is a hard, transparent mineral. It is a compound of aluminum, silica, and fluorine. Gem topaz is valuable. Jewelers call this variety of the stone precious topaz. The best-known precious topaz gems range in color from rich yellow to light brown
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考研背诵50篇——39 The Salinity of Ocean Waters
If the salinity of ocean waters is analyzed, it is found to vary only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the
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考研背诵50篇——40 Cohesion-tension Theory
Atmospheric pressure can support a column of water up to 10 meters high. But plants can move water much higher; the sequoia tree can pump water to its very top more than 100 meters above the ground. Until the end of the nineteenth century, the moveme
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考研背诵50篇——41.American black bears
American black bears appear in a variety of colors despite their name. In the eastern part of their range, most of these brown, red, or even yellow coats. To the north, the black bear is actually gray or white in color. Even in the same litter, both
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考研背诵50篇——42.Coal-fired power plants
The invention of the incandescent light bulb by Thomas A. Edison in 1879 created a demand for a cheap, readily available fuel with which to generate large amounts of electric power. Coal seemed to fit the bill, and it fueled the earliest power statio
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考研背诵50篇——43.Statistics
There were two widely divergent influences on the early development of statistical methods. Statistics had a mother who was dedicated to keeping orderly records of government units (states and statistics come from the same Latin root status) and a ge
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考研背诵50篇——44.Obtaining Fresh water from icebergs
The concept of obtaining fresh water from icebergs that are towed to populated areas and arid regions of the world was once treated as a joke more appropriate to cartoons than real life. But now it is being considered quite seriously by many nations,
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