DELTA I Lat.. from Ck. Aii.ra, fourth letter of the alphabet. anything shaped like the letter _X, from Heb. dateth, door, name of the fourth hotter of the alphabetl, An alluvial plain occurring at the mouth of a river. The name was applied originally by the I:reeks to the land area at the mouth of the Nile from the resemblance in shape to their letter _S. All rivers carry finely divided sand and mud in suspension, and, as their cur rents are checked upon entering quieter waters, the solid particles are deposited upon the hat tom of the channels near the river-mouths. Ti e deposit gradually increases in area and also in thickness until it remlies the surface. and then by floods and by growth it till-. I he)011(1 111O11% of high Meter. Al the head of each land area thus built up. divides into diverging forming a tri angle, the of 11111111 fronts upon the sea. A delta 11 ay at the j WW1 14411 of rivers or at the entrattee of .1 river into sea or lake; a fan-shaped deposit re-embling a delta is some times found. also. where river debouelies from wuntainous. region upon a plain. The large delta.. are found at the of great rivers which di-charge into comparatively quiet seas. t'oa-tal currents and strong tidal action re the river depo-its before they accumulate to any considerable thickness. The area of a delta Va.
rie- with the site of the river, the amount of sediment carried and the length of time it has been deposited, and the relative quietude of the sea. The combined delta of the I;anges and Bralimaputra in 11141ia occupies- more than 30, 111)U miles, and the deposit has been found in places to be nearly 300 feet thick: that of the Nile is 2.041 miles wide at the base of the :\lediter raneati sea and Ilto mile- long. The .\lississippi delta is irregular in form, hut it :Il•ord, a time illustration of the manner in which a river ex Channel ..(..:111N:1111. Its area i• about 12. 3n11 square miles, and it is advaneing into the Gulf of Nlexico at the rate of about 260 feet a year. In Italy the Po has constructed a delta so rapidly that the city which in ancient times was a port of spirit-lent importance to have given it- name to the .kdriat it- Sea, is now about 13 inland. Delta are usually fertile, but by reason of their low elevation they are un healthful and their cultivation is hindered by during storm, and tloods. Consult I:eikie. r/-Hook of (,'t ology (1,ondoti, 18931. See 111vEn: SuonE.