An Elementary Class-Book of General Geography (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER II PHYSICAL GEOGRAPHY 20. The Earth is a great ball a little less than 8000 miles, or rather more than 500,000,000 inches in diameter. It is often said to be a sphere, but a sphere is a mathematical figure every point on the surface of which is equally distant from the centre. In the case of the Earth, however, the distance from either pole to the centre is 13 miles less than from the equator to the centre. Hence the form of our planet is more correctly spoken of as an oblate spheroid, that is, a flattened sphere-like body. But not only is it flattened at the poles, its equator is not a perfect circle with every point on it equidistant from the centre. Sumatra and Ecuador, for instance, are believed to be 1 mile nearer the centre of the Earth than the west coast of Africa or the central Pacific Ocean. Moreover, the surface of the Earth is covered with irregular elevations rising into continents and mountain ranges, and with depressions that sink to form the ocean basins. As all mathematical figures are perfectly smooth, it is therefore more accurate to call the shape of the Earth that of a ball than of a sphere or spheroid. Yet the form of our planet is so like a sphere that in any model small enough to be seen as a whole the irregularity could not be detected by the eye or touch, for the polar diameter is only gth shorter than the equatorial, while the highest mountain is only yth of the Earth's diameter. The circumference of the Earth at the equator is the longest distance that can be traversed on the planet in a direct line, and it measures a little less than 25,000 miles, or rather more than 40,000 kilometres. 21. Natural Divisions of the Earth.?The Earth is really composed of three distinct parts, lying on the whole one over another like the coats of an on...