SONE  , or Sox, a

river of central India which has been identified with the Erannoboas of the Greek geographers . With the exception of the Jumna it is the chief tributary of the Ganges on its right bank . It rises in the Amarkantak highlands about 3500 ft. above sea-level, the Nerbudda and Mahanadi also having their sources in the same table-land . From this point it flows north-west through an intricate mass of hills, until it strikes the Kaimur range, which constitutes the southern wall of the Gangetic plain . Here it turns east and continues in that direction until it falls into the Ganges about Io m. above Patna, after a total course of 465 M . Its upper waters drain about 300 M. of wild hilly country, which has been imperfectly explored; while in its lower section of 16o m. it traverses the British districts of Mirzapur, Shahabad, Gaya and Patna . The Sone canals, fed by the river, form a great system of irrigation in the province of Behar . The headworks are situated at Dehri about 25 M. below the point where the river leaves the hilly ground . The weir across the Sone at this point is believed to be the longest constructed in a single unbroken piece of masonry, the length between abutments being 12,469 ft . A main canal is taken off on either bank of the river, and each of these is divided into branches, according to the requirements of the ground . The system consists of some 370 M. of canals and 1200 M. of distributaries, irrigating 555,000 acres . The Sone canals were begun in 1869, and came into operation in 1874; they form a valuable protection to the rice crop of Behar .