花了点时间：竟然最难做的是第二个句子，想了很久。如有错误，请指正。

Within the span of a hundred years, in the seventeenth and early eighteenth centuries, a tide of emigration -one of the great folk wanderings of history-swept from Europe to America. 46) This movement, impelled (命题人改写为driven) by powerful and diverse motivations, built a nation out of a wilderness and, by its nature, shaped the character and destiny of an uncharted continent.

受到各种强大的动机所驱使，这场运动在荒野中开创了一个国家；本质使然，它也塑造了这片未知大陆的性格和命运。

     47) The United States is the product of two principal forces-the immigration of European peoples with their varied ideas, customs, and national characteristics and the impact of a new country which modified these distinctly European cultural (命题人删除了这三个词)traits. 有两股主要力量形成了美国：一是欧洲移民带来的各式思想、风俗和民族特征，二是这个新国家本身在融合上述特征之后带来的影响。Of necessity, colonial America was a projection of Europe. Across the Atlantic came successive groups of Englishmen, Frenchmen, Germans, Scots, Irishmen, Dutchmen, Swedes, and many others who attempted to transplant their habits and traditions to the new world. 48) But, inevitably,(命题人删掉了这个词) the force of geographic conditions peculiar to America, the interplay of the varied national groups upon one another, and the sheer difficulty of maintaining old-world ways in a raw, new continent caused significant changes. 但是，美国特有的地理条件、不同种族间的相互影响、以及在这片原始的新大陆上维持旧秩序的艰难，带来了巨大的变化。These changes were gradual and at first scarcely visible. But the result was a new social pattern which, although it resembled European society in many ways, had a character that was distinctly American.

    49)The first shiploads of immigrants bound for the territory which is now the United States crossed the Atlantic more than a hundred years after the fifteenth- and sixteenth-century explorations of North America.十五世纪和十六世纪的探索发现了北美洲，又过了一百多年，第一艘满载移民的航船跨过大西洋驶向这片土地，即现在的美国。 In the meantime, thriving Spanish colonies had been established in Mexico, the West Indies, and South America. These travelers to North America came in small, unmercifully overcrowded craft. During their six- to twelve-week voyage, they subsisted on meager rations. Many of the ships were lost in storms, many passengers died of disease, and infants rarely survived the journey. Sometimes tempests blew the vessels far off their course, and often calm brought interminable delay.

    To the anxious travelers the sight of the American shore brought almost inexpressible relief. Said one chronicler, "The air at twelve leagues' distance smelt as sweet as a new-blown garden." The colonists' first glimpse of the new land was a vista of dense woods. 50) The virgin forest with its profusion (命题人把这个词改为richness) and variety of trees was a veritable (命题人把这个词改为real) treasure-house which extended over 1,300 miles from Maine in the north to Georgia (命题人把这个部分改为：from Maine all the way down to Georgia) 原始的森林，有着种类繁多的林木，从缅因州往南一直绵延到乔治亚州，的确是一座宝库。in the south. Here was abundant fuel and lumber. Here was the raw material of houses and furniture, ships and potash, dyes and naval stores.