202 The Great Indian Arc of Meridian, [No. 3, 



that the earth is of a globular form, Newton was tbe first who 

 demonstrated that it is not a perfect sphere. From theoretical 

 considerations, and also from the discovery that a pendulum moves 

 slower at the equator than in higher latitudes, he arrived at the 

 conclusion that its form is that of an oblate spheroid. Modern 

 science has confirmed this, and in several ways determined the 

 depression of the pole to a considerable degree of minuteness ; and 

 this is looked upon as well established, because the amount of 

 depression, though determined in ways quite independent of each 

 other, is very nearly the same in all. (1). Upon the hypothesis 

 that the earth was once fluid, and by assuming a (very probable) 

 law of density of its mass, the depression has been found to be 

 l-300th part of the radius at the equator. (2). By pendulum- 

 experiments made in many parts of the earth, the determination is 

 l-288th part. (3.) From the effect of the protuberant parts of 

 the earth's mass on the motion of the Moon in latitude and longi- 

 tude, Laplace made the depression very slightly less than l-300th. 

 (4.) By the measurement of arcs of the meridian in different parts 

 of the world and the latitudes of their extremities, and comparing 

 arcs in high latitudes with arcs in low latitudes (which has always 

 been considered necessary to eliminate certain errors of observation), 

 the depression has been found to be slightly less than l-300th of 

 the equatorial radius. These are so nearly alike that the question 

 has been considered settled, that the earth's figure is an oblate 

 spheroid, and that its ellipticity is 1 -300th. To be sure we see 

 mountains and valleys, and table-lands and oceans, and every kind 

 of surface. But these have been compared for insignificance to 

 the unevennesses on the coat of an orange, and are indeed still 

 more trifling in comparison. 



3. — But both Physical and Practical Geology have brought new 

 ideas to light. Though the earth no doubt was once fluid, it must 

 be countless ages since it was so. The crust, if the mass be not 

 solid to tbe centre, is of great thickness, as the only real calcu- 

 lations on the subject — those by Mr. Hopkins of Cambridge — show. 

 It is discovered that the earth does not, though solid, preserve an in- 

 variable form. It is a well established fact that in some parts its 

 surface is at present undergoing slow depression, while other parts 



