INTRODUCTION. 23 



the sea, confined or lying between two shores, and opening a pas- 

 sage out of one sea into another, as the strait of Gibraltar, or that of 

 Magellan. This is sometimes called a sound, as the strait into the 

 Baltic. A gulf is a part of the sea running up into the land, and 

 surrounded by it except at the passage by which it communicates 

 with the sea or ocean. If a gulf be very large, it is called an inland 

 sea, as the Mediterranean ; if ft do not go far into the land, it is 

 called a bay, as the bay of Biscay ; if it be very small, a creek, haven, 

 station, or road for ships, as Milford Haven. Rivers, canals, brooks, 

 £cc. need no description ; for these lesser divisions of water, like 

 those of land, are to be met with in most countries, and every one 

 has a clear idea of what is meant by them. But in order to ' 

 strengthen the remembrance of the great parts of the land and 

 water we have described, it may be proper to observe that there is 

 a strong analogy or resemblance between them. The description 

 of a continent resembles that of an ocean ; an island encompassed 

 with water resembles a lake encompassed with land. A peninsula 

 of land is like a gulf or inland sea. A promontory or cape of land 

 is like a bay or creek of the sea ; and an isthmus, whereby two lands 

 ■are joined, resembles a strait, which unites one sea to another. 



OF THE TRUE FIGURE AND DIMENSIONS OF 

 THE EARTH. 



Though we have hitherto spoken of the earth as a spherical 

 or globular body, it is necessary to observe that it is not a perfect 

 sphere. Its true figure was the subject of great disputes between 

 the philosophers of the last age, among whom sir Isaac Newton, 

 and Cassini, a celebrated French astronomer, were the leaders of 

 two different parties. Sir Isaac showed, from mathematical prin- 

 ciples, that the earth must be an oblate spheroid, or that it was 

 flatted at the poles and jutted out towards the equator, so that a 

 line drawn through the centre of the earth, and passing through the 

 poles, would not be so long as a line drawn through the same cen- 

 tre, and passing through the east and west points. The French 

 mathematician asserted precisely the reverse, that is, that its diame- 

 ter was lengthened towards the poles. In order to decide this 

 question, the king of France, in 1736, sent out some able mathemati- 

 cians to Lapland, to measure the length of a degree of latitude at 

 the polar circle, and likewise others to Peru, to make the same 

 admeasurement near the equator. Their observations confirmed 

 the opinion of sir Isaac Newton beyond dispute, and proved that the 

 earth is flatter towards the poles than towards the equator. The 

 nature of sir Isaac's reasoning may be in some measure elucidated 

 by the simple experiment of fixing a ball of soft clay on a spindle, 

 and whirling it round, for we shall find that it will jut out or pro- 

 ject towards the middle, and flatten towards the poles. Sir Isaac, 

 from his theory, had determined that the polar diameter of the earth 

 must be to the equatorial as 229 to 230, or about 35 miles shorter. 

 Maupertuis, and the other French mathematicians who went to 

 Lapland, deduced, from their mensuration of a degree, that the 

 equatorial diameter is 7942 miles, and the polar 7852 miles ; so that 

 the former exceeds the latter by 90 miles. 



According to these calculations, the circumference of the earth 

 under the equator will be 24,951 miles, which multiplied by the di~ 



