THE FIGURE OF THE EARTH. 29 



as the measurement of a degree or the movements of our 

 satellite. The concentric, elliptical, and individually hotno- 

 geneous strata, which increase in density according to certain 

 functions of distance from the surface toward the centre of 

 the earth, may give rise to local fluctuations in the intensity 

 of gravity at individual^oints of the earth's surface, which 

 differ according to the character, position, and density of the 

 several points. If the conditions which produce these devi- 

 ations are much more recent than the consolidation of the 

 outer crust, the figure of the surface can not be assumed to 

 be locally modified by the internal motion of the fused masses. 

 The difference of the results of pendulum measurements is, 

 however, much too great to be ascribed at the present day 

 to errors of observation. Even where a coincidence in the 

 results, or an obvious regularity, has been discovered by 

 the various grouping and combination of the points of ob- 

 servation, the pendulum always gives a greater §]lipticity 

 (varying between the limits -^^5 ^^^ niu) ^^^^^ could have 

 been deduced from the measurements of a degree. 



If we take the ellipticity which, in accordance with Bes- 

 sel's last determination, is now generally adopted, namely, 

 2T¥-T5^> we shall find that the bulging* at the equator 



* In Grecian antiquity two regions of the earth were designated as 

 being characterized, in accordance with the prevalent opinions of the 

 time, by remarkable protuberances of the surface, namely, the high 

 north of Asia and the land lying under the equator. *'The high and 

 naked Scythian plains," says Hippocrates (De AereetAgvis, § xix., p. 

 72, Littre), "without being crowned by mountains, stretch far upward 

 to the meridian of the Bear." A similar opinion had previously been 

 ascribed to Empedocles (Phit., De Plac. Philos., ii., 3). Aristotle {Me- 

 teor., i., 1 a 15, p. 66, Ideler) says that the older meteorologists, ac- 

 cording to whose opinions the sun "did not go under the earth, but 

 passed round it," considered that the protuberances of the earth to- 

 ward the north were the cause of the disappearance of the sun, or of 

 the production of night. And in the compilation of the Problems 

 (xxvi., 15, p. 941, Bekker), the cold of the north wind was ascribed to 

 the elevation of the soil in this region of the earth, and in all these 

 passages there is no reference to mountains, but merely to a bulging 

 of the earth into elevated plateaux. I havie already elsewhere shown 

 {Asie Centrale, t. i., p. 58) that Strabo, who alone makes use of the 

 very characteristic word dpoiridia, says that the difference of climate 

 which arises from geographical position must every where be distin- 

 guished fftm that which we ascribe to elevation above the sea, in 

 Armenia (xi., p. 522, Casaub.), in Lycaonia, which is inhabited by 

 wild asses (xii., p. 568), and in Upper India, in the auriferous country 

 of the Derdi (xv., p, 706). "Even in southern parts of the world," 

 says the geographer of Amasia, " every high district, if it be also a 

 plain, is cold" (ii., p. 73). Eratosthenes andPolybius ascribe the very 



