46) This movement，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.
47)The United States is the product of two principal forces-the immigration of European people with their varied ideas, customs, and national characteristics and the impact of a new country which modified these traits.
48)But 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.
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 15th- and -16th-century explorations of North American.
50)The virgin forest with its richness and variety of trees was a real treasure-house which extended from Maine all the way down to Georgia.