GEOID (from Gr. yij, the

See also:

• EARTH
• EARTH (a word common to Teutonic languages, cf. Ger. Erde, Dutch aarde, Swed. and Dan. jord; outside Teutonic it appears only in the Gr. 'pq'e, on the ground; it has been connected by some etymologists with the Aryan root ar-, to plough, which is seen in
• EARTH, FIGURE OF
• EARTH, FIGURE OF THE

earth)  , an imaginary surface employed by geodesists which has the property that every element of it is perpendicular to the plumb-line where that line cuts it . Compared with the " spheroid of reference " the surface of the geoid is in general depressed over the oceans and raised over the great land masses . (See EARTH, FIGURE OF THE.) GEOK-TEPE, a former fortress of the Turkomans, in Russian Transcaspia, in the oasis of Akhal-tekke, on the Transcaspian railway, 28 m . N.W. of Askabad . It consisted of a walled enclosure in circuit, the wall being 18 ft. high and 20 to 30 ft. thick . In December r88o the place was attacked by 6000 Russians under General Skobelev, and after a siege of twenty-three days was carried by storm, although the defenders numbered 25,000 . A monument and a small museum com- memorate the event .