第一类

1. The same thing happens to this day, though on a smaller scale, wherever a sediment-laden river or stream emerges from a mountain valley onto relatively flat land, dropping its load as the current slows: the water usually spreads out fanwise, depositing the sediment in the form of a smooth, fan-shaped slope.

2. In lowland country almost any spot on the ground may overlie what was once the bed of a river that has since become buried by soil; if they are now below the water’s upper surface (the water table), the gravels and sands of the former riverbed, and its sandbars, will be saturated with groundwater.

3. But note that porosity is not the same as permeability, which measures the ease with which water can flow through a material; this depends on the sizes of the individual cavities and the crevices linking them.

4. If the pores are large, the water in them will exist as drops too heavy for surface tension to hold, and it will drain away; but if the pores are small enough, the water in them will exist as thin films, too light to overcome the force of surface tension holding them in place; then the water will be firmly held.

5. But the myths that have grown up around the rites may continue as part of the group’s oral tradition and may even come to be acted out under conditions divorced from these rites.

6. Another, advanced in the twentieth century, suggests that humans have a gift for fantasy, through which they seek to reshape reality into more satisfying forms than those encountered in daily life.

7. For example, one sign of this condition is the appearance of the comic vision, since comedy requires sufficient detachment to view some deviations from social norms as ridiculous rather than as serious threats to the welfare of the entire group.

8. Timberline trees are normally evergreens, suggesting that these have some advantage over deciduous trees (those that lose their leaves) in the extreme environments of the upper timberline.

9. This is particularly true for trees in the middle and upper latitudes, which tend to attain greater heights on ridges, whereas in the tropics the trees reach their greater heights in the valleys.

10. As the snow is deeper and lasts longer in the valleys, trees tend to attain greater heights on the ridges, even though they are more exposed to high-velocity winds and poor, thin soils there.

11. Wind velocity also increases with altitude and may cause serious stress for trees, as is made evident by the deformed shapes at high altitudes.

12. Some scientists have proposed that the presence of increasing levels of ultraviolet light with elevation may play a role, while browsing and grazing animals like the ibex may be another contributing factor.

13. Probably the most important environmental factor is temperature, for if the growing season is too short and temperatures are too low, tree shoots and buds cannot mature sufficiently to survive the winter months.

14. Immediately adjacent to the timberline, the tundra consists of a fairly complete cover of low-lying shrubs, herbs, and grasses, while higher up the number and diversity of species decrease until there is much bare ground with occasional mosses and lichens and some prostrate cushion plants.

15. In order for the structure to achieve the size and strength necessary to meet its purpose, architecture employs methods of support that, because they are based on physical laws, have changed little since people first discovered them-even while building materials have changed dramatically.

16. Some of the world’s finest stone architecture can be seen in the ruins of the ancient Inca city of Machu Picchu high in the eastern Andes Mountains of Peru.

17. It works in compression to divert the weight above it out to the sides, where the weight is borne by the vertical elements on either side of the arch.

18. The Ogallala aquifer is a sandstone formation that underlies some 583,000 square kilometers of land extending from northwestern Texas to southern South Dakota.

19. Unfortunately, the cost of water obtained through any of these schemes would increase pumping costs at least tenfold, making the cost of irrigated agricultural products from the region uncompetitive on the national and international markets.

20. Whatever the final answer to the water crisis may be, it is evident that within the High Plains, irrigation water will never again be the abundant, inexpensive resource it was during the agricultural boom years of the mid-twentieth century.

21. To take an extreme example, farmlands dominated by a single crop are so unstable that one year of bad weather or the invasion of a single pest can destroy the entire crop.

22. Ecologists are especially interested to know what factors contribute to the resilience of communities because climax communities all over the world are being severely damaged or destroyed by human activities.

23. The destruction caused by the volcanic explosion of Mount St. Helens, in the northwestern United States, for example, pales in comparison to the destruction caused by humans.

24. Many ecologists now think that the relative long-term stability of climax communities comes not from diversity but from the “patchiness” of the environment, an environment that varies from place to place supports more kinds of organisms than an environment that is uniform.

25. Similarly, a plant or animal cannot squander all its energy on growing a big body if none would be left over for reproduction, for this is the surest way to extinction.

26. At the other extreme are “competitors,” almost all of whose resources are invested in building a huge body, with a bare minimum allocated to reproduction.

27. A new plant will spring up wherever a seed falls on a suitable soil surface, but because they do not build big bodies, they cannot compete with other plants for space, water, or sunlight.

28. These plants are termed opportunists because they rely on their seeds’falling into settings where competing plants have been removed by natural processes, such as along an eroding riverbank, on landslips, or where a tree falls and creates a gap in the forest canopy.

29. Human landscapes of lawns, fields, or flowerbeds provide settings with bare soil and a lack of competitors that are perfect habitats for colonization by opportunists.

30. A massive oak claims its ground for 200 years or more, outcompeting all other would-be canopy trees by casting a dense shade and drawing up any free water in the soil. 

31.It should be noted, however, that the pure opportunist or pure competitor is rare in nature, as most species fall between the extremes of a continuum,exhibiting a blend of someopportunistic and some competitivecharacteristics.

32.Because some paintings were made directly over others, obliterating them,it is probable that apainting’s value ended with the migration it pictured.

33.One Lascaux narrative picture, which shows aman with a birdlike headand a wounded animal, would seem to lendcredence to this third opinion,but there is still much that remainsunexplained.

34.Perhaps so much time has passed that there will never be satisfactoryanswers to the cave images,but their mystique only adds to theirimportance.

35.In 1994 there were nearly 20,000 wind turbines worldwide, most groupedin clusters called wind farmsthat collectively produced 3,000 megawatts ofelectricity.

36.Most were in Denmark (whichgot 3 percent of its electricity from windturbines) and California (where 17,000 machines produced 1 percent ofthe state’s electricity,enough to meet the residential needs of a city aslarge as San Francisco).

37.In the long run, electricity from large wind farms in remote areas might beused to make hydrogen gas fromwater during periods when there is lessthan peak demand forelectricity.

38.Large wind farms might also interfere with the flight patterns of migratorybirds in certain areas, andthey have killed large birds of prey (especiallyhawks, falcons, and eagles)that prefer to hunt along the same ridge linesthat are ideal for windturbines.

39.David Douglas, Scottish botanical explorer of the 1830s ， found adisturbing change in theanimal life around the fort during the periodbetween his first visit in 1825and his final contact with the fort in 1832.

40.The researchers Peter Ucko and Andree Rosenfeld identified threeprincipal locations ofpaintings in the caves of western Europe: (1) inobviously inhabited rockshelters and cave entrances; (2) in galleriesimmediately off the inhabitedareas of caves; and (3) in the inner reachesof caves, whose difficulty ofaccess has been interpreted by some as asign that magical-religiousactivities were performed there.

41.Perhaps, like many contemporary peoples, Upper Paleolithic men andwomen believed that thedrawing of a human image could cause death orinjury, and if that wereindeed their belief, it might explain why humanfigures are rarely depicted incave art.

42.For example, wild cattle (bovines) and horses are portrayed more oftenthan we would expect bychance, probably because they were larger andheavier (meatier) than otheranimals in the environment.

43.Consistent with this idea, according to the investigators, is the fact that theart of the cultural periodthat followed the Upper Paleolithic also seems toreflect how people got theirfood.

44.But in that period, when getting food no longer depended on hunting largegame animals (because theywere becoming extinct), the art ceased tofocus on portrayals of animals.

45.When the well reaches a pool, oil usually rises up the well because of itsdensity difference with waterbeneath it or because of the pressure ofexpanding gas trapped above it.

46.More than one-quarter of the world’s oil and almost one-fifth of the world’snatural gas come fromoffshore, even though offshore drilling is six toseven times more expensivethan drilling on land.

47.While there are a dozen or more mass extinctions in the geological record,the Cretaceous mass extinctionhas always intrigued paleontologistsbecause it marks the end ofthe age of the dinosaurs.

48.The explosion lifted about 100 trillion tons of dust into the atmosphere, ascan be determined by measuringthe thickness of the sediment layerformed when this dust settledto the surface.

49.Such a quantity of material would have blocked the sunlight completelyfrom reaching the surface,plunging Earth into a period of cold anddarkness that lasted at leastseveral months.

50.The explosion is also calculated to have produced vast quantities of nitricacid and melted rock thatsprayed out over much of Earth, startingwidespread fires that musthave consumed most terrestrial forests andgrassland.

51.Following each mass extinction, there is a sudden evolutionary burst asnew species develop to fillthe ecological niches opened by the event.

52.Earth is a target in a cosmic shooting gallery, subject to random violent events that were unsuspected afew decades ago.

53.Early in the century, a pump had come into use in which expanding steamraised a piston in a cylinder，and atmospheric pressure brought it downagain when the steam condensedinside the cylinder to form a vacuum．

54. Thefinal step came when steam was introduced into the cylinder to drivethe piston backward as well asforward thereby increasing the speed of theengine and cutting its fuelconsumption.

55.Iron manufacturers which had starved for fuel while depending on charcoalalso benefited fromever-increasing supplies of coal; blast furnaces withsteam- powered bellows turnedout more iron and steel for the newmachinery.

56.He received rudimentary village schooling but mostly he roamed hisuncle's farm collecting thefossils that were so abundant in the rocks of theCotswold hills．

57.The companies building the canals to transport coal needed surveyors tohelp them find the coaldeposits worth mining as well as to determine thebest courses for the canals.

58.In 1831 when Smith was finally recognized by the Geological Society ofLondon as the “father ofEnglish geology”, it was not only for his maps butalso for something even moreimportant．

59.Maturation of the frontal lobes of the brain continues throughout earlychildhood, and this part ofthe brain may be critical for rememberingparticular episodes in waysthat can be retrieved later.

60.Demonstrations of infants’ and toddlers' long-term memory have involvedtheir repeating motoractivities that they had seen or done earlier，such asreaching in the dark for objects, puttinga bottle in a doll’s mouth, or pullingapart two pieces of a toy.

61.Through hearing stories with a clear beginning，middle, and endingchildren may learn to extract the gist ofevents in ways that they will beable to describe many yearslater.

62.The world looks very different to a person whose head is only two or threefeet above the ground than toone whose head is five or six feet above it,0lder children and adultsoften try to retrieve the names of things they saw,but infants would not haveencoded the information verbally．

63.General knowledge of categories of events such as a birthday party or avisit to the doctor's officehelps older individuals encode their experiences,but again, infants andtoddlers are unlikely to encode many experienceswithin such knowledgestructures．

64.Physiological immaturity may be part of why infants and toddlers do notform extremely enduring memories,even when they hear stories thatpromote such remembering inpreschoolers.

65.In 1947 Norwegian adventurer Thor Heyerdahl drifted on a balsa-log raftwestward with the winds andcurrents across the Pacific from SouthAmerica to prove his theorythat Pacific islanders were Native Americans (also called American Indians).

66.Contrary to the arguments of some that much of the pacific was settled byPolynesians accidentallymarooned after being lost and adrift, it seemsreasonable that this feat wasaccomplished by deliberate colonizationexpeditions that set out fullystocked with food and domesticated plantsand animals.

67.The undisputed pre-Columbian presence in Oceaniaof the sweet potato,which is a New Worlddomesticate, has sometimes been used to supportHeyerdahl’s “American Indiansin the Pacific” theories.

68.As Patrick Kirch, an American anthropologist, points out, rather than beingbrought by rafting SouthAmericans, sweet potatoes might just have easilybeen brought back by returningPolynesian navigators who could havereached the west coast of South America.

69.Conditions that promote fossilization of soft-bodied animals include veryrapid covering by sedimentsthat create an environment that discouragesdecomposition.

70.This 700-million-year-old formation gives few clues to the origins ofmodern animals, however,because paleontologists believe it representsan evolutionary experimentthat failed.

71.At one time, the animals present in these fossil beds were assigned tovarious modern animal groups,but most paleontologists now agree that allTommotian fossils representunique body forms that arose in the earlyCambrian period anddisappeared before the end of the period, leaving nodescendants in modern animalgroups.

72.These fossil beds provide evidence of about 32 modern animal groups,plus about 20 other animalbody forms that are so different from anymodern animals that theycannot be assigned to any one of the moderngroups.

73.With question such as these clearly before them, the scientists aboard theGlomar Challenger processed tothe Mediterranean to search for theanswers.

74.In all probability it was the fertile plain of Latium, where the Latins whofounded Rome originated, that created the habits andskills of landedsettlement, landed property, landed economy, landedadministration, and aland-based society.

75.Agriculture seems to have reached these people from the Near East, sincethe first domesticated crops were milletsand sorghums whose origins arenot African but west Asian.

76.Most of Africa presents a curious case in which societies moved directlyfrom a technology of stone toiron without passing through the intermediatestage of copper or bronzemetallurgy, although some early copper-workingsites have been found in West Africa.

77.They spoke a language, prior-Bantu (“Bantu” means “the people”), which isthe parent tongue of alanguage of a large number of Bantu languages still spoken throughout sub-Sahara Africa.

78.Why and how these people spread out into central and southern Africaremains a mystery, butarchaeologists believe that their iron weaponsallowed them to conquer theirhunting-gathering opponents, who still usedstone implements.

79.With Cuicuilco eliminated as a potential rival, any one of a number ofrelatively modest towns mighthave emerged as a leading economic andpolitical power in Central Mexico.

80.The hard volcanic stone was a resource that had been in great demand formany years, at least since therise of the Olmecs (a people who flourishedbetween 1200 and 400 B.C.),and it apparently had a secure market.

81.Moreover, recent research on obsidian tools found at Olmecs sites hasshown that some of theobsidian obtained by the Olmecs originated nearTeotihuacán.

82.The growing power of the elite, who controlled the economy, would givethem the means to physicallycoerce people to move to Teotihuacán andserve as additions to the laborforce.

83.By measuring how many of these meteorites fall to Earth over a givenperiod of time, scientists canestimate how long it might have taken todeposit the observed amount oflr in the boundary clay.

84.They bear a strong resemblance to river systems on Earth, and geologiststhink that they are dried-upbeds of long-gone rivers that once carriedrainfall on Mars from themountains down into the valleys.

85.Runoff channels on Mars speak of a time 4 billion years ago (the age of theMartian highlands), when theatmosphere was thicker, the surface warmer,and liquid water widespread.

86.The onrushing water arising from these flash floods likely also formed theodd teardrop-shaped “islands”(resembling the miniature versions seen inthe wet sand of our beaches atlow tide) that have been found on theplains close to the ends ofthe outflow channels.

87.Judging from the width and depth of the channels, the flow rates musthave been trulyenormous―perhaps as much as a hundred times greaterthan the 105 tons per secondcarried by the great Amazon river.

88. Acomputer-generated view of the Martian north polar region shows theextent of what may have beenan ancient ocean covering much of thenorthern lowlands.

89.Proponents point to features such as the terraced “beaches” shown in oneimage, which could conceivablyhave been left behind as a lake or oceanevaporated and the shorelinereceded.

90.But detractors maintain that the terraces could also have been created bygeological activity, perhapsrelated to the geologic forces that depressedthe Northern Hemisphere farbelow the level of the south, in which casethey have nothing whatever todo with Martian water.

91.It has long been accepted that the Americaswere colonized by a migration of peoples from Asia, slowlytraveling across a land bridge called Beringia(now the Bering Strait betweennortheastern Asia and Alaska)during thelast Ice Age.

92.The first water craft theory about the migration was that around11,000-12,000 years ago therewas an ice-free corridor stretching fromeastern Beringia to the areasof North America south of the great northernglaciers.

93.But belief in this ice-free corridor began to crumble when paleoecologistGlen MacDonald demonstratedthat some of the most importantradiocarbon dates used to support theexistence of an ice-free corridorwere incorrect.

94.He theorized that with the use of watercraft, people gradually colonizedunglaciated refuges and areasalong the continental shelf exposed by thelower sea level.

95.Fladmark's hypothesis received additional support from the fact that thegreatest diversity in NativeAmerican languages occurs along the westcoast of the Americans,suggesting that this region has been settled thelongest.

96.Vast areas along the coast may have been deglaciated beginning around16,000 years ago, possiblyproviding a coastal corridor for the movementof plants, animals, and humanssometime between 13,000 and 14,000years ago.

97.The coastal hypothesis has gained increasing support in recent yearsbecause the remains of largeland animals, such as caribou and brownbears, have been found insoutheastern Alaskadating between 10,000and 12,500 years ago.

98.Fladmark and others believe that the first human colonization of Americaoccurred by boat along theNorthwest Coast during the very late Ice Age,possibly as early as 14,000years ago.

99.The most recent geologic evidence indicates that it may have beenpossible for people tocolonize ice-free regions along the continental shelfthat were still exposed by thelower sea level between 13,000 and 14,000ago.

100.They were concerned that many would be drawn to these new,refreshing conceptions ofteaching only to find that the void between theabstractions and the realitiesof teacher reflection is too great to bridge.

101.Further observation revealed the tendency of teachers to evaluateevents rather than review thecontributory factors in a considered mannerby, in effect, standingoutside the situation.

102.The researchers estimate that the initial training of the same teachersto view events objectivelytook between 20 and 30 hours, with the samenumber of hours again beingrequired to practice the skills of reflection.

103.The teachers in the program described how they found it difficult to putaside the immediate demands ofothers in order to give themselves the time they needed to developtheir reflective skills.

104.Support and encouragement were also required to help teachers in theprogram cope with aspects oftheir professional life with which they werenot comfortable.

105.The fungi absorb moisture and mineral salts from the rocks, passingthese on in waste productsthat nourish algae.

106. Lichenshelped to speed the decomposition of the hard rock surfaces,preparing a soft bed of soilthat was abundantly supplied with minerals thathad been carried in the moltenrock from the bowels of Earth.

107.By means of these seeds, plants spread more widely to new locations,even to isolated islands likethe Hawaiian archipelago, which lies morethan 2,000 miles west of California and 3,500 miles east of Japan.

108.Although we now tend to refer to the various crafts according to thematerials used to constructthem-clay, glass, wood, fiber, and metal-it wasonce common to think of craftsin terms of function, which led to their beingknown as the "appliedarts."

109.Since the laws of physics, not some arbitrary decision, havedetermined the general form ofapplied-art objects, they follow basicpatterns, so much so thatfunctional forms can vary only within certainlimits.

110.That this device was a necessary structural compromise is clear fromthe fact that the cannonballquickly disappeared when sculptors learnedhow to strengthen the internalstructure of a statue with iron braces (ironbeing much stronger thanbronze).

111.Even though the fine arts in the twentieth century often treat materialsin new ways, the basicdifference in attitude of artists in relation to theirmaterials in the fine arts andthe applied arts remains relatively constant.

112.Pakicetus was found embedded in rocks formed from river depositsthat were 52 million years old.

113.The structure of the backbone shows, however, that Ambulocetusswam like modern whales bymoving the rear portion of its body up anddown, even though a fluke wasmissing.

114.The impact of raindrops on the loose soil tends to transfer fine clayparticles into the tiniestsoil spaces, sealing them and producing a surfacethat allows very little waterpenetration.

115.The gradual drying of the soil caused by its diminished ability to absorbwater results in the furtherloss of vegetation, so that a cycle of progressivesurface deterioration isestablished.

116.During the dry periods that are common phenomena along the desertmargins, though, the pressureon the land is often far in excess of itsdiminished capacity, anddesertification results.

117.The increased pressures of expanding populations have led to theremoval of woody plants sothat many cities and towns are surrounded bylarge areas completely lackingin trees and shrubs.

118.The increasing use of dried animal waste as a substitute fuel has alsohurt the soil because thisvaluable soil conditioner and source of plantnutrients is no longer beingreturned to the land.

119.In areas where considerable soil still remains, though, a rigorouslyenforced program of landprotection and cover-crop planting may make itpossible to reverse thepresent deterioration of the surface.

120.The cinema did not emerge as a form of mass consumption until itstechnology evolved from theinitial "peepshow" format to the point whereimages were projected on ascreen in a darkened theater.

121.It was designed for use in Kinetoscope parlors, or arcades, whichcontained only a fewindividual machines and permitted only one customerto view a short, 50-foot filmat any one time.

122.In the phonograph parlors, customers listened to recordings throughindividual ear tubes, movingfrom one machine to the next to hear differentrecorded speeches or pieces ofmusic.

123.He refused to develop projection technology, reasoning that if he madeand sold projectors, thenexhibitors would purchase only one machine-aprojector-from him instead ofseveral.

124.But the movies differed significantly from these other forms ofentertainment, which dependedon either live performance or (in the caseof the slide-and-lanternshows) the active involvement of a master ofceremonies who assembled thefinal program.

125.Although early exhibitors regularly accompanied movies with live acts,the substance of the moviesthemselves is mass-produced, prerecordedmaterial that can easily bereproduced by theaters with little or no activeparticipation by the exhibitor.

126.Even though early exhibitors shaped their film programs by mixingfilms and other entertainmentstogether in whichever way they thoughtwould be most attractive toaudiences or by accompanying them withlectures, their creativecontrol remained limited.

127.With the advent of projection, the viewer's relationship with the imagewas no longer private, as ithad been with earlier peepshow devices suchas the Kinetoscope and theMutoscope, which was a similar machine thatreproduced motion by means ofsuccessive images on individualphotographic cards instead of on strips ofcelluloid.

128.At the same time, the image that the spectator looked at expandedfrom the minuscule peepshowdimensions of 1 or 2 inches (in height) tothe life-size proportions of 6or 9 feet.

129.Those individuals who possess characteristics that provide them withan advantage in the strugglefor existence are more likely to survive andcontribute their genes to thenext generation.

130.Because aggressive individuals are more likely to survive andreproduce, whatever genes arelinked to aggressive behavior are morelikely to be transmitted tosubsequent generations.

131.Children normally desire to vent aggressive impulses on other people,including their parents,because even the most attentive parents cannotgratify all of their demandsimmediately.

132.People decide whether they will act aggressively or not on the basis offactors such as theirexperiences with aggression and their interpretationof other people's motives.

133.Factory life necessitated a more regimented schedule, where workbegan at the sound of a belland workers kept machines going at aconstant pace.

134.One mill worker who finally quit complained revealingly about"obedience to theding-dong of the bell-just as though we are so manyliving machines."

135.Unlike artisan workshops in which apprentices worked closely with themasters supervising them,factories sharply separated workers frommanagement.

136.More than a decade of agitation did finally bring a workday shortenedto 10 hours to most industriesby the 185O’s, and the courts alsorecognized workers' right tostrike, but these gains had little immediateimpact.

137.When not in use, the fins are tucked into special grooves ordepressions so that they lieflush with the body and do not break up itssmooth contours.

138.They must also keep swimming to keep from sinking, since most havelargely or completely lost theswim bladder, the gas-filled sac that helpsmost other fish remain buoyant.

139.The development of the modern presidency in the United States beganwith Andrew Jackson who sweptto power in 1829 at the head of theDemocratic Party and serveduntil 1837.

140.The Fore also displayed familiar facial expressions when asked howthey would respond if theywere the characters in stories that called forbasic emotional responses.

141.Ekman and his colleagues more recently obtained similar results in astudy of ten cultures in whichparticipants were permitted to report thatmultiple emotions were shownby facial expressions.

142.According to this hypothesis, signals from the facial muscles("feedback) are sent backto emotion centers of the brain, and so aperson's facial expression caninfluence that person's emotional state.

143.But when the emotion that leads to stiffening the lip is more intense,and involves strong muscletension, facial feedback may heightenemotional response.

144.Hills and mountains are often regarded as the epitome of permanence,successfully resisting thedestructive forces of nature, but in fact they tendto be relatively short-livedin geological terms.

145.About 400 million years ago, when the present-day continents of North America and Europe werejoined, the Caledonian mountain chain was thesame size as the modern Himalayas.

146.Glaciers may form in permanently cold areas, and these slowly movingmasses of ice cut out valleys,carrying with them huge quantities of erodedrock debris.

147.Fuller devised a type of dance that focused on the shifting play of lightsand colors on the voluminous skirtsor draperies she wore, which she keptin constant motion principallythrough movements of her arms, sometimesextended with wands concealedunder her costumes.

148.Although her early theatrical career had included stints as an actress,she was not primarilyinterested in storytelling or expressing emotionsthrough dance; the drama ofher dancing emanated from her visual effects.

149.Although she discovered and introduced her art in the United States,she achieved her greatestglory in Paris,where she was engaged by theFolies Bergere in 1892 and soon became “La Loie,” the darling of Parisianaudiences.

150.Her interest in color and light paralleled the research of several artistsof the period, notably thepainter Seurat, famed for his Pointillist techniqueof creating a sense of shapesand light on canvas by applying extremelysmall dots of color ratherthan by painting lines.

151.Although she gave little thought to music in her earliest dances, shelater used scores by Gluck,Beethoven, Schubert, Chopin, and Wagner,eventually graduating toStravinsky, Faure, Debussy, and Mussorgsky,composers who were thenconsidered progressive.

152.Always open to scientific and technological innovations, shebefriended the scientistsMarie and Pierre Curie upon their discovery ofradium and created a RadiumDance, which simulated thephosphorescence of that element.

153.Although she is remembered today chiefly for her innovations in stagelighting, her activities alsotouched Isadora Duncan and Ruth St. Denis,two other United Statesdancers who were experimenting with new typesof dance.

154.They may change color with changing light conditions and cloud cover,glowing pink or gold in the morningor evening light, but this color changeis generally related to thelow angle of the Sun above the horizon.

155.one explanation for green icebergs attributes their color to an opticalillusion when blue ice isilluminated by a near-horizon red Sun, but greenicebergs stand out among whiteand blue icebergs under a great variety oflight conditions.

156.The scientists concluded that green icebergs form when a two-layerblock of shelf ice breaks awayand capsizes (turns upside down), exposingthe bubble-free shelf ice thatwas formed from seawater.

157.A green iceberg that stranded just west of the Amery Ice Shelf showedtwo distinct layers: bubblyblue-white ice and bubble-free green ice separated by a one-meter-longice layer containing sediments.